RESUMEN
The present study was designed to examine the effects of prenatal stress on the morphological development of sexually dimorphic structures in the anterior hypothalamus in male rats and to determine if there is a relationship between morphologic development of the brain and copulatory behavior in individual animals. Dams in the stress group were subjected to treatments of heat-light restraint during the third trimester of gestation (day 14 to parturition) three times daily for 45-min periods. At 90 days of age, prenatally stressed and control male offspring were tested during the dark cycle for spontaneous male sexual behavior. Volumes of the sexually dimorphic nucleus of the preoptic area (SDN-POA) and the anteroventral periventricular nucleus (AVPV) were measured. Comparisons were made between copulatory behavior and hypothalamic nuclear volumes. SDN-POA volumes were significantly reduced (feminized; males have a larger SDN-POA than females) in prenatally stressed males that did not copulate, whereas, SDN-POA volumes in prenatally stressed males that copulated were not altered. The few control males that did not copulate (sexually non-active) also had significantly reduced SDN-POA volumes compared to the control males that did copulate (sexually active). The volume of the AVPV was significantly increased (feminized; males have a smaller AVPV than females) in prenatally stressed males that were sexually non-active compared to AVPV volumes in sexually active males. The results obtained in this study provide a strong positive relationship between sexual behavior and the morphology of the two sexually dimorphic structures measured.
Asunto(s)
Hipotálamo/anatomía & histología , Complicaciones del Embarazo/psicología , Efectos Tardíos de la Exposición Prenatal , Conducta Sexual Animal/fisiología , Estrés Psicológico , Animales , Copulación/fisiología , Eyaculación/fisiología , Femenino , Edad Gestacional , Calor , Hipotálamo/fisiología , Iluminación , Masculino , Núcleo Hipotalámico Paraventricular/anatomía & histología , Embarazo , Área Preóptica/anatomía & histología , Ratas , Ratas Sprague-Dawley , Restricción Física , Caracteres SexualesRESUMEN
The purpose of the present study was to determine the effects of sexual behaviorial manipulation on brain plasticity in adult male rats. Adult male Sprague-Dawley rats that copulated during male sexual behavior testing were divided into four groups: control male; gonadectomized (Gdx) male; sexually active male; and sexually nonactive male. Female animals were used as an additional control group. At the end of a 12-week experimental period, the animals were again tested for male sexual behavior and tested for sexual motivation. Sexual behavior manipulations over the 12-week period resulted in significant differences in mount latency, mount frequency, intromission latency, intromission frequency, ejaculation latency, and the postejaculation interval. In the motivation test, significant differences in the number of approaches, contacts, and crossings of an electrified grid separating the test animal from a receptive female were also observed. Sexually dimorphic nucleus of the preoptic area (SDN-POA) volumes in sexually nonactive males were significantly smaller than in control males or sexually active males. Anteroventral periventricular nucleus (AVPV) volumes in the male groups were not significantly altered by sexual behavioral manipulations, however, the nonactive AVPV vol. was the only vol. not significantly different from the control female vol. These data demonstrate that in the adult rat, sexual behavioral manipulations resulted in significant alterations in behavior and in the vol. of the SDN-POA and that the effect of sexual behavior on the AVPV needs to be further investigated.
Asunto(s)
Plasticidad Neuronal/fisiología , Área Preóptica/fisiología , Caracteres Sexuales , Conducta Sexual Animal/fisiología , Animales , Peso Corporal/fisiología , Electrochoque , Femenino , Masculino , Motivación , Tamaño de los Órganos/fisiología , Ratas , Ratas Sprague-DawleyRESUMEN
Photically evoked after-discharge (PhAD) bursting was examined in albino rats following either bilateral or unilateral dorsal frontal lesions. The initial effect of either type of frontal lesion was to significantly suppress PhAD occurrence. However, after repeated exposure to the PhAD recording environment no difference could be seen between the lesioned and control animals. In addition, no difference in PhAD could be detected between the two visual cortices in any of the groups. Spontaneous alternation and open-field activity were also tested. Both frontally lesioned groups of animals were significantly more active than control animals in the initial stages of testing. These findings indicate that the frontal cortex can inhibit brain stem mechanisms which are responsible for behavioral arousal and the modulation of hypersynchronous bursting in the cortex. However, because no difference was seen between the two visual cortices in any of the groups, it is suggested that this mechanism is not a strictly unilateral mechanism.
Asunto(s)
Conducta Animal/fisiología , Lóbulo Frontal/fisiología , Corteza Visual/fisiología , Animales , Electrofisiología , Estimulación Luminosa , Ratas , Ratas Endogámicas , Corteza Visual/citologíaRESUMEN
Photically evoked after-discharge (PhAD) bursting was examined in lightly restrained albino rats following frontal and mid-cortical lesions. The initial effect of dorsal frontal lesions was to significantly suppress PhAD occurrence. Spontaneous activity as measured on an open-field arena was examined as a second variable. Frontally lesioned animals were significantly more active than mid-cortically lesioned and non-lesioned control animals in the initial stages of behavioral testing. These results indicate that the frontal cortex has an inhibitory influence on reticular formation (rf) arousal mechanisms which are responsible for behavioral arousal and the modulation of hypersynchronous burst-like phenomena occurring at the level of the cortex.