RESUMEN
A growing body of evidence suggests that the alpha7 neuronal nicotinic receptor (NNR) subtype is an important target for the development of novel therapies to treat schizophrenia, offering the possibility to address not only the positive but also the cognitive and negative symptoms associated with the disease. In order to probe the relationship of alpha7 function to relevant behavioral correlates we employed TC-5619, a novel selective agonist for the alpha7 NNR subtype. TC-5619 binds with very high affinity to the alpha7 subtype and is a potent full agonist. TC-5619 has little or no activity at other nicotinic receptors, including the alpha4beta2, ganglionic (alpha3beta4) and muscle subtypes. The transgenic th(tk-)/th(tk-) mouse model that reflects many of the developmental, anatomical, and multi-transmitter biochemical aspects of schizophrenia was used to assess the antipsychotic effects of TC-5619. In these mice TC-5619 acted both alone and synergistically with the antipsychotic clozapine to correct impaired pre-pulse inhibition (PPI) and social behavior which model positive and negative symptoms, respectively. Antipsychotic and cognitive effects of TC-5619 were also assessed in rats. Similar to the results in the transgenic mice, TC-5619 significantly reversed apomorphine-induced PPI deficits. In a novel object recognition paradigm in rats TC-5619 demonstrated long-lasting enhancement of memory over a wide dose range. These results suggest that alpha7-selective agonists such as TC-5619, either alone or in combination with antipsychotics, could offer a new approach to treating the constellation of symptoms associated with schizophrenia, including cognitive dysfunction.
Asunto(s)
Conducta Animal/efectos de los fármacos , Benzofuranos/uso terapéutico , Trastornos del Conocimiento/tratamiento farmacológico , Neuronas/metabolismo , Agonistas Nicotínicos/uso terapéutico , Quinuclidinas/uso terapéutico , Receptores Nicotínicos/fisiología , Esquizofrenia/tratamiento farmacológico , Psicología del Esquizofrénico , Animales , Antipsicóticos/farmacología , Antipsicóticos/uso terapéutico , Benzofuranos/farmacología , Clozapina/farmacología , Clozapina/uso terapéutico , Trastornos del Conocimiento/metabolismo , Trastornos del Conocimiento/psicología , Conducta Exploratoria/efectos de los fármacos , Femenino , Masculino , Aprendizaje por Laberinto/efectos de los fármacos , Ratones , Ratones Transgénicos , Agonistas Nicotínicos/farmacología , Regiones Promotoras Genéticas , Quinuclidinas/farmacología , Ratas , Ratas Sprague-Dawley , Receptor Tipo 1 de Factor de Crecimiento de Fibroblastos/biosíntesis , Receptor Tipo 1 de Factor de Crecimiento de Fibroblastos/genética , Reflejo de Sobresalto/efectos de los fármacos , Esquizofrenia/metabolismo , Conducta Social , Tirosina 3-Monooxigenasa/genética , Receptor Nicotínico de Acetilcolina alfa 7RESUMEN
Vasopressin affects behavior via its two brain receptors, the vasopressin 1a and vasopressin 1b receptors (Avpr1b). Recent work from our laboratory has shown that disruption of the Avpr1b gene reduces intermale aggression and reduces social motivation. Here, we further characterized the aggressive phenotype in Avpr1b -/- (knockout) mice. We tested maternal aggression and predatory behavior. We also analyzed the extent to which food deprivation and competition over food increases intermale aggression. We quantified defensive behavior in Avpr1b -/- mice and later tested offensive aggression in these same mice. Our results show that attack behavior toward a conspecific is consistently reduced in Avpr1b -/- mice. Predatory behavior is normal, suggesting that the deficit is not because of a global inability to detect and attack stimuli. Food deprivation, competition for food and previous experience increase aggression in both Avpr1b +/+ and -/- mice. However, in these circumstances, the level of aggression seen in knockout mice is still less than that observed in wild-type mice. Defensive avoidance behaviors, such as boxing and fleeing, are largely intact in knockout mice. Avpr1b -/- mice do not display as many 'retaliatory' attacks as the Avpr1b +/+ mice. Interestingly, when territorial aggression was measured following the defensive behavior testing, Avpr1b -/- mice typically show less initial aggressive behavior than wild-type mice, but do show a significant increase in aggression with repeated testing. These studies confirm that deficits in aggression in Avpr1b -/- mice are limited to aggressive behavior involving the attack of a conspecific. We hypothesize that Avpr1b plays an important role in the central processing that couples the detection and perception of social cues (which appears normal) with the appropriate behavioral response.
Asunto(s)
Agresión/fisiología , Agresión/psicología , Receptores de Vasopresinas/genética , Animales , Conducta Competitiva/fisiología , Señales (Psicología) , Femenino , Masculino , Conducta Materna , Ratones , Ratones Noqueados , Conducta Predatoria/fisiologíaRESUMEN
Two receptors for vasopressin (Avp) are expressed in the brain, the Avp 1a receptor (Avpr1a) and the Avp 1b receptor (Avpr1b). To investigate the role of Avpr1a in behaviors in mice more extensively, we generated a line of mice lacking a functional Avpr1a (knockout, Avpr1a(-/-)). We first performed a baseline phenotypic screen of the Avpr1a knockouts followed by a more detailed analysis of their circadian rhythms and olfactory function. When free-running in constant darkness, the Avpr1a(-/-) mice have a longer circadian tau than the wild types. There are also subtle olfactory deficits in Avpr1a(-/-) mice as measured in an olfactory habituation/dishabituation test and in the discrimination of female urine from male urine using an operant testing paradigm. An extensive body of research has shown that manipulation of the Avpr1a alters behavior, including aggression and social recognition. Therefore, we expected profound behavioral deficits in mice lacking the Avpr1a gene. Contrary to our expectations, social aggression, anxiety-like behavior and social recognition are unaffected in this line of Avpr1a knockout mice. These data suggest either that the Avpr1a is not as critical as we thought for social behavior in mice or, more likely, that the neural circuitry underlying aggression and other social behaviors compensates for the life-long loss of the Avpr1a. However, the olfactory deficits observed in the Avpr1a(-/-) mice suggest that Avp and Avpr1a drugs may affect behavior, in part, by modulation of chemosensory systems.
Asunto(s)
Conducta Animal/fisiología , Ritmo Circadiano/fisiología , Aprendizaje Discriminativo/fisiología , Receptores de Vasopresinas/fisiología , Olfato/fisiología , Conducta Social , Agresión/fisiología , Animales , Presión Sanguínea/fisiología , Condicionamiento Operante/fisiología , Femenino , Genética Conductual , Habituación Psicofisiológica , Masculino , Conducta Materna/fisiología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Receptores de Vasopresinas/genética , Reconocimiento en Psicología/fisiologíaRESUMEN
The vasopressin 1b receptor (Avpr1b) is one of two principal receptors mediating the behavioral effects of vasopressin (Avp) in the brain. Avpr1b has recently been shown to strongly influence social forms of aggression in mice and hamsters. This receptor appears to play a role in social recognition and motivation as well as in regulating the hypothalamic-pituitary-adrenal axis. Most of these studies have been performed in knockout mice, a species in which the localization of the Avpr1b has not been described, thus precluding correlations with the behaviors. We performed in situ hybridization histochemistry (ISHH) with specific probes and found especially prominent expression within the CA2 pyramidal neurons of the hippocampus, with much lower expression in the hypothalamic paraventricular nucleus and amygdala. Reverse transcriptase-polymerase chain reaction (RT-PCR) confirmed expression in those as well other areas in which the ISHH was not sensitive enough to detect labeled cells (e.g. piriform cortex, septum, caudate-putamen and lower brainstem areas). Mouse Avpr1b transcript levels were not altered in the CA2 field by restraint stress or adrenalectomy. Finally, ISHH and RT-PCR showed expression of the Avpr1b gene in the rat and human hippocampi as well. We suggest that the CA2 field may form or retrieve associations (memories) between olfactory cues and social encounters.
Asunto(s)
Corticoesteroides/metabolismo , Hipocampo/anatomía & histología , Hipocampo/metabolismo , Receptores de Vasopresinas/genética , Estrés Psicológico/metabolismo , Vasopresinas/metabolismo , Corteza Suprarrenal/metabolismo , Adrenalectomía , Adulto , Animales , Encéfalo/metabolismo , Encéfalo/fisiopatología , Modelos Animales de Enfermedad , Femenino , Regulación de la Expresión Génica/genética , Hipocampo/fisiopatología , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Persona de Mediana Edad , Hipófisis/metabolismo , Hipófisis/fisiopatología , ARN Mensajero/metabolismo , Ratas , Restricción Física , Especificidad de la Especie , Estrés Psicológico/genética , Estrés Psicológico/fisiopatologíaRESUMEN
Increased aggression is commonly associated with many neurological and psychiatric disorders. Current treatments are largely empirical and are often accompanied by severe side effects, underscoring the need for a better understanding of the neural bases of aggression. Vasopressin, acting through its 1a receptor subtype, is known to affect aggressive behaviors. The vasopressin 1b receptor (V1bR) is also expressed in the brain, but has received much less attention due to a lack of specific drugs. Here we report that mice without the V1bR exhibit markedly reduced aggression and modestly impaired social recognition. By contrast, they perform normally in all the other behaviors that we have examined, such as sexual behavior, suggesting that reduced aggression and social memory are not simply the result of a global deficit in sensorimotor function or motivation. Fos-mapping within chemosensory responsive regions suggests that the behavioral deficits in V1bR knockout mice are not due to defects in detection and transmission of chemosensory signals to the brain. We suggest that V1bR antagonists could prove useful for treating aggressive behavior seen, for example, in dementias and traumatic brain injuries.
Asunto(s)
Agresión/fisiología , Conducta Animal/fisiología , Química Encefálica/genética , Receptores de Vasopresinas/genética , Factores de Edad , Animales , Temperatura Corporal/fisiología , Corticosterona/sangre , Ingestión de Alimentos/fisiología , Conducta Exploratoria/fisiología , Femenino , Masculino , Aprendizaje por Laberinto/fisiología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Actividad Motora/fisiología , Neuronas/química , Fenotipo , Proteínas Proto-Oncogénicas c-fos/análisis , Reconocimiento en Psicología/fisiología , Conducta Sexual Animal/fisiología , Estrés Fisiológico/fisiopatología , Testosterona/sangre , Percepción Visual/fisiologíaRESUMEN
Pheromones are an important class of environmental cues that affect the hypothalamic-pituitary-gonadal axis in a variety of vertebrate species, including humans. When male mice contact female-soiled bedding, or urine, they display a reflexive luteinizing hormone (LH) surge within 30 min. Aside from the requirement that males have gonads to show this response, the physiological mechanisms that underlie this pituitary response are unknown. In this experiment, we asked if female pheromones acted at the level of gonadotropin-releasing hormone (GnRH) gene expression to affect this hormone response. In addition, we also examined the contribution of one of the oestrogen receptors (ERalpha) by studying this neuroendocrine reflex in wild-type and oestrogen receptor-alpha knockout (ERalphaKO) males. Both ERalphaKO and wild-type males showed the expected LH surge, 45 and 90 min after contact with female pheromones. Males housed in clean bedding or bedding soiled by another adult male did not display the LH elevation. Interestingly, this dramatic change in LH concentrations was not accompanied by any alterations in GnRH mRNA expression or levels of primary transcript in the preoptic area-anterior hypothalamus. The one exception to this was a significant increase in GnRH mRNA expression in tissue collected from wild-type males exposed to bedding from another male. This is particularly intriguing since LH was not elevated in these males. These data replicate and extend our previous finding that ERalphaKO males do exhibit an LH surge in response to female pheromones. Thus, this neuroendocrine response is regulated by a steroid receptor other than ERalpha and does not require alterations in GnRH mRNA expression.
Asunto(s)
Hormona Liberadora de Gonadotropina/genética , Hormona Luteinizante/sangre , Receptores de Estrógenos/genética , Atractivos Sexuales/farmacología , Animales , Receptor alfa de Estrógeno , Receptor beta de Estrógeno , Femenino , Expresión Génica/efectos de los fármacos , Expresión Génica/fisiología , Genotipo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Hipófisis/efectos de los fármacos , Hipófisis/fisiología , Procesamiento Postranscripcional del ARN/efectos de los fármacos , Procesamiento Postranscripcional del ARN/fisiología , ARN Mensajero/metabolismo , Receptores de Estrógenos/metabolismo , Conducta Sexual Animal/efectos de los fármacos , Conducta Sexual Animal/fisiología , Orina/químicaRESUMEN
Estrogen receptor alpha (ERalpha) is believed to be a critical part of the regulatory processes involved in normal reproduction and sexual behavior. However, in this study we show the ERalpha is not required for display of masculine sexual behavior. Male and female, ERalpha knock-out (ERalphaKO) and wild-type mice were gonadectomized and implanted with testosterone. Sexual behavior and social preferences were tested after injection of the dopamine agonist, apomorphine (APO), or vehicle. All wild-type mice showed normal masculine behavior, including mounts and pelvic thrusts in females, and ejaculation in males. In agreement with past reports, ERalphaKO mice, given vehicle, failed to show mating behavior. Yet, ERalphaKO males given APO showed masculine copulatory behavior and chemoinvestigatory behavior directed at females. ERalphaKO females, treated with APO, mounted and thrusted when tested with receptive females. HPLC revealed that wild-type and ERalphaKO mice had equivalent catecholamine content in brain regions associated with masculine sexual behavior. These data show that the ERalpha is not essential during development or adulthood for the expression of masculine sexual behavior in mice. Moreover, dopamine can activate sexual behavior via a mechanism that either acts on an ER other than ERalpha or via an estrogen-independent pathway.
Asunto(s)
Dopamina/farmacología , Receptores de Estrógenos/fisiología , Conducta Sexual Animal/efectos de los fármacos , Animales , Química Encefálica/fisiología , Catecolaminas/metabolismo , Cromatografía Líquida de Alta Presión , Copulación/fisiología , Receptor alfa de Estrógeno , Femenino , Genotipo , Masculino , Ratones , Ratones Noqueados , Orquiectomía , Receptores de Estrógenos/genética , Caracteres Sexuales , Medio SocialRESUMEN
The expression of normal masculine sexual behaviour requires testosterone. Testosterone can bind to androgen receptors, either in its native form, or after reduction to other androgen metabolites. In addition, testosterone can be aromatized to oestrogen, and bind to oestrogen receptor alpha and/or beta. Male copulatory behaviour is deficient in mice lacking functional oestrogen receptor alpha gene (ERalphaKO mice). We sought to determine which aspect(s) of masculine sexual behaviour is compromised in the ERalphaKOs. Specifically, we asked whether ERalphaKO males have reduced motivation and/or an inability to recognize oestrous females. We found significant differences between mice of different genotypes in the amount of chemo-investigatory behaviour displayed and in the target of their investigation. Wild-type males spent more time investigating ovariectomized, oestradiol-treated females, than either males, or ovariectomized females that had not received hormone priming. ERalphaKO males spent little time investigating any of the stimulus mice and showed no preferences. To test the hypothesis that this lack of chemo-investigatory behaviour is due to the inability of ERalphaKO males to detect and respond to female pheromones, we exposed males to chemosensory cues (soiled bedding) from females. Males resided in clean, or female-soiled, cage bedding for 60 min. Next, blood was collected and plasma luteinizing hormone (LH) assayed. We also assessed Fos-like immunoreactivity (Fos-ir) in several neural regions involved in processing chemosensory cues. Despite the fact that male ERalphaKOs spend little time engaged in chemo-investigation of females, their neuroendocrine responses to female-soiled bedding were similar to those seen in wild-type males. Our data suggest that the normal coupling between the neuroendocrine response to females and the generation of sexual behaviour is disrupted in ERalphaKO mice. Responses to female pheromones do not require ERalpha. However, normal male sexual performance requires the ERalpha gene.
Asunto(s)
Hormona Luteinizante/sangre , Feromonas/fisiología , Receptores de Estrógenos/genética , Receptores de Estrógenos/metabolismo , Olfato/fisiología , Animales , Receptor alfa de Estrógeno , Conducta Alimentaria/fisiología , Femenino , Fórnix/química , Fórnix/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Bulbo Olfatorio/química , Bulbo Olfatorio/metabolismo , Hipófisis/química , Hipófisis/metabolismo , Área Preóptica/química , Área Preóptica/metabolismo , Proteínas Proto-Oncogénicas c-fos/metabolismo , Núcleos Septales/química , Núcleos Septales/metabolismo , Factores Sexuales , Área Tegmental Ventral/química , Área Tegmental Ventral/metabolismoRESUMEN
Estrogens are an important class of steroid hormones, having multiple targets, in the body and brain, and exerting ubiquitous effects on behavior. At present, two estrogen receptors (ERalpha and beta) have been cloned and sequenced in mammals. In the brain these receptors are regionally specific, but both have widespread distributions, which are largely non-overlapping. Given the newly emerging complexities of estrogen's mechanisms of action it is important to distinguish which pathways are involved in modifying which behaviors. We use a knockout mouse, lacking functional copies of the estrogen receptor alpha (ERalpha) gene, to study the mechanisms by which estrogens mediate behaviors. There are pronounced ramifications of ERalpha gene disruption on behavior. First, female ERalpha knockout (ERalphaKO) mice do not display normal feminine sexual behavior. Second, treatment of adult mice with androgens promotes masculine sexual behavior in both sexes. However, male-typical sexual behavior is severely compromised in male and female ERalphaKOs. Third, male ERalphaKOs do not exhibit the same social preferences for female mice as do wildtype (WT) littermates. Thus, the ERalpha is essential for normal expression of sexual behaviors. In addition, gonadectomized ERalphaKO and WT mice rapidly learn to escape from the Morris water maze. Exogenous estrogen treatment prevents WT females from learning this task, yet, has no effect in ERalphaKO mice, suggesting that estrogens effects on learning in adult females involves the ERalpha. Based on these data we hypothesize that ERalpha mediates many of the effects of estrogen on sexual behavior, learning, and memory.
Asunto(s)
Estrógenos/genética , Estrógenos/fisiología , Ratones Noqueados/fisiología , Receptores de Estrógenos/genética , Receptores de Estrógenos/fisiología , Conducta Sexual Animal/fisiología , Animales , Receptor alfa de Estrógeno , Femenino , Masculino , Ratones , Ratones Noqueados/genéticaRESUMEN
Steroid hormones regulate levels of gonadotropin mRNA in the pituitary, and gonadotropic hormones in plasma. To determine whether estrogen receptor alpha (ERalpha) mediates steroid negative feedback, wild type (WT) and estrogen receptor alpha knockout (ERalphaKO) mice of both sexes were gonadectomized and implanted with a Silastic capsule containing either estradiol (E2), dihydrotestosterone (DHT), testosterone, or a blank capsule. Ten days later, plasma luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels were measured. Pituitary mRNA levels of gonadotropin subunit (alpha, LHbeta, FSHbeta) and prolactin (PRL) were quantified. LH levels in gonad-intact ERalphaKO females were elevated, similar to values seen following gonadectomy. By contrast, serum LH concentrations in gonad-intact ERalphaKO males were low and rose following gonadectomy, suggesting androgen feedback. Estradiol treatment significantly decreased plasma LH in WT animals, but not in ERalphaKOs. In fact, in female ERalphaKOs, our dose of E2 increased plasma levels of LH as compared with untreated, ovariectomized ERalphaKOs. All the steroid treatments suppressed LH in WT animals whereas only DHT consistently suppressed LH concentrations in ERalphaKO mice. The postgonadectomy rise in plasma FSH was prevented by steroid treatments in WT females, but not in any of the other groups. Gonadotropin subunit and PRL mRNA responses to E2 treatment (both inhibitory and stimulatory) were absent in ERalphaKO mice, suggesting a critical role for ERalpha. Although E2 can exert negative feedback effects on LH release in both males and females by actions at the ERalpha, the androgen receptor plays the primary physiological role in the male mouse.
Asunto(s)
Hormona Folículo Estimulante/sangre , Gonadotropinas/metabolismo , Hormona Luteinizante/sangre , Receptores de Estrógenos/fisiología , Esteroides/fisiología , Animales , Dihidrotestosterona/farmacología , Estradiol/farmacología , Receptor alfa de Estrógeno , Retroalimentación/fisiología , Femenino , Hormona Folículo Estimulante/metabolismo , Expresión Génica , Hormona Luteinizante/metabolismo , Masculino , Ratones , Ratones Noqueados , Hipófisis/metabolismo , Prolactina/genética , Prolactina/metabolismo , ARN Mensajero/metabolismo , Receptores Androgénicos/fisiología , Receptores de Estrógenos/efectos de los fármacos , Esteroides/farmacología , Testosterona/farmacologíaRESUMEN
A carnivore, the ferret possesses a vomeronasal organ--accessory olfactory bulb (VNO-AOB) projection to the hypothalamus; however, little is known about its function. Pheromones in soiled bedding from estrous female ferrets or an artificial peppermint odor significantly augmented nuclear Fos protein immunoreactivity (Fos-IR), a marker of neural activation, in several main olfactory bulb (MOB) sites but not in the AOB of gonadectomized male and females. Testosterone propionate (TP) significantly augmented the MOB's neuronal Fos responses to estrous females' pheromones, but not to peppermint. Estrous odors, but not peppermint, also augmented neuronal Fos-IR in the medial preoptic area (mPOA) of female, but not male, subjects. Pheromones in soiled bedding from breeding male ferrets significantly augmented neuronal Fos-IR in the MOB and in the medial amygdala of gonadectomized, TP-treated male and female subjects. Again, male pheromones failed to influence neuronal Fos-IR in the AOB of either sex, and only females showed significant increases in neuronal Fos-IR in the lateral aspect of the ventromedial nucleus and mPOA. These results point to an essential role among higher mammals of the main olfactory epithelium-MOB projection to the hypothalamus in detecting and processing pheromones. Gonadectomized ferrets showed significant increases in sniffing behavior when placed on either female or male bedding. This occurred regardless of whether they had received TP or oil vehicle, suggesting that testosterone's facilitation of neuronal Fos responses to estrous females' odors in the MOB of both sexes cannot be attributed to increased scent gathering. Androgen receptor-IR was present in the MOB granule cell layer of male and female ferrets, raising the possibility that testosterone acts directly on these cells to augment their responsiveness to pheromones.
Asunto(s)
Hurones/metabolismo , Hipotálamo/metabolismo , Bulbo Olfatorio/metabolismo , Feromonas/farmacología , Proteínas Proto-Oncogénicas c-fos/biosíntesis , Testosterona/farmacología , Animales , Conducta Animal/fisiología , Estro/fisiología , Femenino , Masculino , Mentha piperita , Neuronas/metabolismo , Odorantes , Extractos Vegetales , Proteínas Proto-Oncogénicas c-fos/análisis , Caracteres SexualesRESUMEN
In many mammalian species the neuroendocrine regulation of male and female reproductive behavior is sexually dimorphic. By contrast, many features of female sexual behavior in the musk shrew (Suncus murinus) more closely resemble those of males than of females of other species. Female musk shrews require testosterone (T), which is neurally aromatized to estrogen, to induce sexual behavior. Aromatization occurs in the medial preoptic area (MPOA), and this region is critical for the expression of female receptivity. To compare neural responses to sexual behavior in females and males, we compared the number of Fos-like immunoreactive (Fos-ir) neurons after mating in musk shrews. In both males and females the number of Fos-ir neurons was increased by mating activity in the granule layer of the accessory olfactory bulb (gr-AOB), the bed nucleus of the stria terminalis (BNST), MPOA, the medial amygdala (MeA), and the region corresponding to the midbrain central tegmental field (CTF). Although Fos was induced by mating in several regions, this response was only dimorphic in the ventral medial nucleus of the hypothalamus (VMN), where mating significantly increased Fos-ir in females, but not in males. In both sexes, only the gr-AOB displayed an increase in Fos-ir after exposure to chemosensory cues alone. Thus, the pattern of Fos expression in the brain after mating is only sexually dimorphic in one region, the VMN. Further, in spite of past behavioral studies done in this species, which show a role for pheromones in induction of receptivity, these data show that exposure to pheromones does not induce Fos in structures caudal to the olfactory bulbs.
Asunto(s)
Neuronas/fisiología , Proteínas Proto-Oncogénicas c-fos/análisis , Conducta Sexual Animal/fisiología , Musarañas/metabolismo , Animales , Biomarcadores/química , Señales (Psicología) , Femenino , Inmunohistoquímica , Masculino , Caracteres SexualesRESUMEN
Mating with intromission induces a prolonged preovulatory LH surge in the estrous female ferret but inhibits LH secretion in the male. We used the dual immunocytochemical localization of Fos (as a marker of neural activation) and tyrosine hydroxylase (TH) to determine whether neurons containing norepinephrine or other catecholamines are activated after mating. Breeding male ferrets were allowed to intromit with estrous females; both animals were perfused 90 min after the onset of intromission. Other male and female ferrets were perfused 90 min after being placed in a cage in which an opposite-sex ferret in breeding condition had previously been housed for 48 h. Control ferrets of each sex were perfused 90 min after being placed alone in a clean testing cage. Mating with intromission significantly augmented the percentage of TH-immunoreactive (TH-IR) neurons colabeled with nuclear Fos-like immunoreactivity (Fos-IR) in both the A6 and the rostral A2 midbrain catecholamine cell groups in females, but not males. Exposure to chemosensory cues alone also increased the percentage of Fos-IR TH neurons in the rostral A2, but not the A6, cell group in females. Chemosensory cues alone did not affect the percentage of double-labeled neurons in either cell group in males. These activated midbrain TH-IR neurons are most likely noradrenergic, and their activation in estrous females may facilitate the mediobasal hypothalamic release of LHRH required for the preovulatory LH surge. In both sexes, mating with intromission, but not chemosensory cues alone, augmented the percentage of periglomerular TH-IR neurons in the main olfactory bulb (MOB) that were colabeled with Fos-IR. These activated TH-IR neurons in the MOB are most likely dopaminergic. Their role in the neural response to mating is currently unknown.
Asunto(s)
Copulación/fisiología , Hurones/fisiología , Mesencéfalo/enzimología , Caracteres Sexuales , Tirosina 3-Monooxigenasa/metabolismo , Animales , Biomarcadores , Femenino , Inmunohistoquímica , Hormona Luteinizante/metabolismo , Masculino , Mesencéfalo/citología , Mesencéfalo/metabolismo , Neuronas/enzimología , Neuronas/metabolismo , Bulbo Olfatorio/citología , Bulbo Olfatorio/enzimología , Bulbo Olfatorio/metabolismo , Ovulación/fisiología , Proteínas Proto-Oncogénicas c-fos/metabolismoRESUMEN
Estrogens are an important class of steroid hormones, involved in the development of brain, skeletal, and soft tissues. These hormones influence adult behaviors, endocrine state, and a host of other physiological functions. Given the recent cloning of a second estrogen receptor (ER) cDNA (the ER beta), work on alternate spliced forms of ER alpha, and the potential for membrane estrogen receptors, an animal with a null background for ER alpha function is invaluable for distinguishing biological responses of estrogens working via the ER alpha protein and those working via another ER protein. Data generated to date, and reviewed here, indicate that there are profound ramifications of the ER alpha disruption on behavior and neuroendocrine function. First, data on plasma levels of estradiol (E2), testosterone (T), and luteinizing hormone (LH) in wild-type (WT) versus ER alpha- mice confirm that ER alpha is essential in females for normal regulation of the hypothalamic-pituitary gonadal axis. Second, ovariectomized female ER alpha- mice do not display sexual receptivity when treated with a hormonal regime of estrogen and progesterone that induces receptivity in WT littermates. Finally, male sexual behaviors are disrupted in ER alpha- animals. Given decades of data on these topics our findings may seem self-evident. However, these data represent the most direct test currently possible of the specific role of the ER alpha protein on behavior and neuroendocrinology. The ER alpha- mouse can be used to ascertain the specific functions of ER alpha, to suggest functions for the other estrogen receptors, and to study indirect effects of ER alpha on behavior via actions on other receptors, neurotransmitters, and neuropeptides.
Asunto(s)
Ratones Noqueados/genética , Receptores de Estrógenos/genética , Conducta Sexual Animal/fisiología , Maduración Sexual/genética , Animales , Femenino , Gónadas/inervación , Sistema Hipotálamo-Hipofisario/fisiología , Masculino , Ratones , Receptores de Estrógenos/fisiología , Maduración Sexual/fisiologíaRESUMEN
The ferret is a reflexively ovulating species in which mating induces a preovulatory LH surge in the estrous female but significantly decreases LH secretion in the breeding male. This sexually dimorphic hormonal response is reflected in a sex difference in Fos-like immunoreactivity (Fos-IR) in forebrain LHRH and non-LHRH neurons after mating. We used dual immunocytochemistry for Fos and LHRH to determine whether the sex dimorphism occurs in the initial detection and transmission or in the central processing of sensory stimuli associated with mating? We also assessed the ability of chemosensory cues alone to augment neuronal Fos-IR in the ferret forebrain. Breeding male and female ferrets were paired, whereupon the male partner achieved an intromission lasting for 16-90 min. Mated male and female subjects were always perfused 90 min after the onset of the male's intromission. Additional male and female subjects were placed alone in a cage in which an opposite sex ferret in breeding condition had been housed for 48 h. Other control ferrets were placed alone in a clean cage. Chemosensory-stimulated and unpaired control subjects were perfused 90 min after being placed in their respective cages. In both sexes mating augmented neuronal Fos-IR in the granular layer of the main olfactory bulb, the caudal thalamic central tegmental field, and the medial amygdala, regions situated early in the putative input pathway to mediobasal hypothalamic LHRH neurons. Neuronal Fos-IR was also increased in these same forebrain regions (the central tegmental field excluded) in both sexes after exposure to chemosensory cues alone. However, more central components of this input pathway, including the preoptic area, the bed nucleus of the stria terminalis, and the ventrolateral portion of the ventromedial hypothalamus as well as the mediobasal hypothalamic LHRH neurons themselves were activated by mating only in the female. In estrous females, exposure only to chemosensory stimuli from a breeding male augmented Fos-IR in the preoptic area and the ventrolateral portion of the ventromedial hypothalamus, but not in the bed nucleus of the stria terminalis or mediobasal hypothalamic LHRH neurons. In breeding males, exposure only to chemosensory cues from an estrous female failed to affect Fos-IR in any of these proximal components of the input pathway or in LHRH neurons themselves. These results suggest that the sex dimorphism in mating-induced LH secretion reflects a sex difference in the central processing of genital-somatosensory stimuli and possibly of chemosensory inputs as well.
Asunto(s)
Células Quimiorreceptoras/fisiología , Hurones/fisiología , Hormona Liberadora de Gonadotropina/metabolismo , Neuronas Aferentes/fisiología , Prosencéfalo/fisiología , Reproducción/fisiología , Caracteres Sexuales , Animales , Femenino , Inmunohistoquímica , Hormona Luteinizante/sangre , Masculino , Neuronas/metabolismo , Neuronas/fisiología , Prosencéfalo/citología , Prosencéfalo/metabolismo , Proteínas Proto-Oncogénicas c-fos/metabolismoRESUMEN
Masculine sexual behavior is regulated by testosterone (T). However, T can be metabolized to form estrogens or other androgens, which then activate their own receptors. We used knockout mice lacking a functional estrogen receptor alpha (ER alpha) gene to test the hypothesis that, following aromatization, T acts via the ER alpha to activate normal masculine sexual behavior. After gonadectomy and T replacement, wild-type (WT) male and female mice displayed masculine behavior. However, given the same T treatment, little masculine behavior was displayed by mice of either sex that lack a normal copy of the ER alpha gene. In particular, the latency to display masculine sex behavior and the number of mount attempts per trial were significantly reduced in the ER alpha- mice compared to WT littermates (P < 0.05). In addition, we found that in both sexes, ER alpha- mice have a smaller cluster of androgen receptor immunoreactivity in the bed nucleus of the stria terminalis. Using adult ER alpha- mice we were unable to determine whether these genotypic differences are due to organizational or activational effects. However, it is clear that the ER alpha plays a key role in the expression of masculine sexual behavior and in the regulation of androgen receptors in a neuronal cell population involved in the display of motivated behaviors.
Asunto(s)
Receptores de Estrógenos/deficiencia , Receptores de Estrógenos/genética , Conducta Sexual Animal/fisiología , Animales , Química Encefálica/genética , Química Encefálica/fisiología , Femenino , Genotipo , Procesamiento de Imagen Asistido por Computador , Inmunohistoquímica , Masculino , Ratones , Orquiectomía , Ovariectomía , Reacción en Cadena de la Polimerasa , Receptores Androgénicos/deficiencia , Receptores Androgénicos/genética , Caracteres SexualesRESUMEN
The mating-induced preovulatory surge of luteinizing hormone (LH) lasts for at least 12 h in the female ferret. This prolonged increase in circulating LH is presumably accompanied by a corresponding elevation in the activity and output of luteinizing hormone-releasing hormone (LHRH) neurons projecting to the hypothalamic-hypophyseal portal blood vessels and adenohypophysis. We used the protein products of the immediate early genes (IEGs) c-fos, and c-jun as markers of neural activation in order to determine whether a sub-population of LHRH neurons is differentially activated by mating and whether non-LHRH neurons in specific forebrain regions are selectively activated at different times during the mating-induced preovulatory LH surge. In Experiment 1, estrous female ferrets were perfused 0.5, 1.5, 3.0, 6.0 or 12.0 h after receiving one 5-min intromission from a male or after being placed alone in a testing cage for 20 min. Fos-like immunoreactivity (Fos-IR; Oncogene Ab-2 antiserum) and LHRH-like immunoreactivity (LHRH-IR; LR-1 antiserum) were visualized. The percentage of Fos-IR LHRH neurons was significantly augmented 1.5 h after mating but had returned to basal levels by 3.0 h. The double-labeled LHRH neurons were concentrated in the caudal medio-basal hypothalamus. In non-LHRH neurons the number of Fos-IR neural nuclei was significantly increased by mating in the medial preoptic area (MPOA), bed nucleus of the stria terminalis (BNST), medial amygdala (MA), ventrolateral hypothalamus (VLH), and midbrain central tegmental field (CTF) 1.5 h after mating but, as in LHRH neurons, had returned to basal levels by 3.0 h. In Experiment 2, estrous females were perfused 1.5 h or 8.0 h after either receiving one 5-min intromission or being placed alone in a testing cage, and the brains were processed for LHRH and c-Fos-like (DCH-1, Dr Gerard Evan), c-Jun-like (Jun-IR; Oncogene Ab-2) or Egr-1-like (Egr-IR; Santa Cruz) immunoreactivity. The percentage of LHRH neurons colabeled with both Fos-IR and Jun-IR was significantly greater in the 1.5 h group than in the unpaired group. Again, the induction of these IEG products occurred in LHRH neurons in the caudal medio-basal hypothalamus. Mating significantly increased the number of Fos-IR non-LHRH neural nuclei in the MPOA, BNST, MA, VMH and CTF, as well as the number of Egr-IR nuclei in the MPOA, BNST and MA in the 1.5 h group. By contrast, the number of Jun-IR non-LHRH neurons was unaffected by mating. In these Experiments we have identified a sub-population of LHRH neurons which, using Fos and Jun as markers of neural activation, is activated by mating and may be differentially involved in the generation of the preovulatory LH surge. Although the LHRH system is presumably activated throughout the duration of the 12 h preovulatory LH surge, c-Fos and c-Jun immunoreactivity in LHRH neurons is augmented only transiently. Fos-IR and Egr-IR in non-LHRH neurons show a similar time-course. Together, these results suggest that the presence of augmented levels of these proteins is not required for the maintenance or termination of the preovulatory output of LHRH.
Asunto(s)
Estro/fisiología , Genes Inmediatos-Precoces/inmunología , Genes Inmediatos-Precoces/fisiología , Hormona Liberadora de Gonadotropina/análisis , Prosencéfalo/química , Conducta Sexual Animal/fisiología , Animales , Especificidad de Anticuerpos , Química Encefálica/genética , Núcleo Celular/química , Proteínas de Unión al ADN/análisis , Proteínas de Unión al ADN/inmunología , Femenino , Hurones , Inmunohistoquímica , Masculino , Neuronas/química , Prosencéfalo/citología , Proteínas Proto-Oncogénicas c-fos/análisis , Proteínas Proto-Oncogénicas c-fos/inmunología , Proteínas Proto-Oncogénicas c-jun/análisis , Proteínas Proto-Oncogénicas c-jun/inmunología , Factores de Tiempo , Factores de Transcripción/análisis , Factores de Transcripción/inmunología , Dedos de Zinc/inmunologíaRESUMEN
Previous research has shown that mating induces the expression of the immediate-early gene, c-fos, as detected by the increased presence of nuclear FOS-like immunoreactivity (FOS-IR), in specific forebrain regions of both male and female rats. In the male both olfactory-vomeronasal (O/V) and genital/somatosensory (G/S) inputs appear to contribute to the neural FOS response to mating whereas in the female G/S input carried by the pelvic nerves appears to mediate the forebrain FOS response. To date, however, no direct sex comparison of the mating-induced forebrain FOS response has been made in rats maintained under the same steroidal conditions nor has the contribution of afferent sensory input from the pelvic nerves been assessed in males. We first compared the level of FOS-IR in brain regions of mated and unpaired gonadectomized male and female rats given 5 micrograms/kg estradiol benzoate (EB) for 7 days and 500 micrograms progesterone (P) 4 h prior to testing. One h after experiencing 1 ejaculation, both sexes showed increased FOS-IR in the medial preoptic a (MPOA), bed nucleus of the stria terminalis (BNST), medial amygdala, the ventro-lateral portion of the ventromedial nucleus of the hypothalamus (VMN), and the midbrain central tegmental field (CTF). This increase was significantly greater in the MPOA and medial amygdala of mated females than of males. Bilateral transection of the pelvic nerves significantly attenuated the increase in FOS-IR after mating in the CTF of male rats and in the MPOA, BNST, VMN, medial amygdala and CTF of females. Thus, following mating there is no sex difference in the brain regions which express c-fos, but there is a dimorphism in the contribution of afferent information conveyed by the pelvic nerves to the mating-induced FOS response. The neural FOS response of the female to mating is heavily dependent upon the G/S afferent inputs carried by the pelvic nerves whereas the male's neural c-fos response may depend on O/V input plus G/S input conveyed via other efferent pathways such as the pudendal nerves.
Asunto(s)
Nervios Periféricos/fisiología , Prosencéfalo/metabolismo , Proteínas Proto-Oncogénicas c-fos/biosíntesis , Conducta Sexual Animal/fisiología , Animales , Eyaculación/fisiología , Estradiol/farmacología , Femenino , Inmunohistoquímica , Masculino , Orquiectomía , Ovariectomía , Área Preóptica/citología , Área Preóptica/fisiología , Prosencéfalo/anatomía & histología , Ratas , Caracteres Sexuales , Núcleos Talámicos/fisiología , Núcleo Hipotalámico Ventromedial/citología , Núcleo Hipotalámico Ventromedial/metabolismoRESUMEN
The nuclear protein product (FOS) of the immediate-early gene, c-fos, was visualized immunocytochemically in the brains of male rats after they either achieved 8 intromissions with an estrous female or were left alone in a test arena. Mating induced equivalent increments in the number of FOS immunoreactive (IR) neurons present in the medial preoptic area (mPOA), the bed nucleus of the stria terminalis (BNST), and the medial amygdala in groups of males that were gonadally intact or had been castrated and treated for 7 days with either testosterone propionate, dihydrotestosterone propionate, estradiol benzoate (EB), or oil vehicle. Equivalent, low numbers of FOS-IR neurons were seen in these brain regions in additional groups of castrated males that received either EB or oil vehicle but were not paired with a female before being killed. Circulating sex steroids apparently contribute little to the mating-induced stimulation of c-fos gene expression, even in brain regions known to contain high levels of androgen and estrogen receptor.