RESUMEN
Cocaine and Amphetamine-Regulated Transcript (CART) is widely expressed in the central nervous system and in several endocrine organs. CART is an important factor in the regulation of energy homeostasis. The aim of the study was to assess the role of CART in physiological response of pituitary cells in a course of starvation. The pituitary cells harvested from starved and fed ad libitum male rats were cultured for 48h and treated with: 0.1nM, 1nM, 10nM or 100nM doses of CART. The medium was collected after 60min and stored at -70°C until samples were further assayed for: LH, FSH, PRL, GH, TSH and ACTH. We revealed that in cultures of pituitary cells collected from fasted rats the basal levels of the examined hormones were reduced. Incubation of pituitary cells of non-starved rats with any dose of CART reduced the concentration of LH and TSH, while the levels of the other hormones were decreased after administration only specific doses of CART. In cells of fasted rats no change in the concentration of gonadotrophins was observed. The PRL level was increased only in the 1nM dose of CART, while the 10nM and 100nM CART doses markedly enhanced GH and TSH. Moreover, administration of 1nM, 10nM and 100nM of CART to cultured cells of fasted rats resulted in a significant rise of the ACTH. Our results indicate that CART can directly affect the physiological release of PRL, ACTH, TSH and GH in pituitary cells of starved animals. Moreover, CART did not alter the LH and FSH suppression level, which is correlated with food deprivation. This data stays in contrast with the already proposed role of CART as an anorexigenic hypothalamic factor.
Asunto(s)
Ayuno , Hambre , Proteínas del Tejido Nervioso/fisiología , Hipófisis/metabolismo , Hormonas Hipofisarias/metabolismo , Animales , Masculino , Proteínas del Tejido Nervioso/farmacología , Hipófisis/efectos de los fármacos , Hormonas Hipofisarias/análisis , Cultivo Primario de Células , Ratas , Ratas Wistar , Estadísticas no ParamétricasRESUMEN
Adiponectin is a protein secreted primarily by adipose tissue. It has been suggested that adiponectin plays a protective role in the early phase following myocardial infarction. Our primary aim was to investigate the effects of post-myocardial infarction heart failure well-characterized by left ventricular hemodynamic parameters on the total and high molecular weight adiponectin concentrations in plasma, fat and cardiac tissue. Eight weeks after myocardial infarction or sham operation, total and high molecular weight adiponectin concentrations in plasma, fat, and cardiac tissues were assayed in rats. In addition, hemodynamic parameters and expression of the genes encoding atrial natriuretic peptide and brain natriuretic peptide in left ventricle were evaluated. Atrial natriuretic peptide and brain natriuretic peptide mRNA levels in left ventricle tissue were higher in rats with myocardial infarction-induced heart failure compared with the controls. Similarly, total adiponectin concentration was increased in left ventricle (but not in right ventricle) in rats with post-myocardial infarction heart failure. In contrast, adiponectin levels in plasma and cardiac adipose tissue in rats with post-myocardial infarction heart failure were lower than in sham-operated animals. Furthermore, there were no significant differences in levels of high molecular weight adiponectin in plasma, cardiac tissue or adipose tissue between these two groups. We conclude that in the rat model of post-myocardial infarction heart failure, adiponectin level is increased in left ventricle tissue. This is accompanied by decreased adiponectin levels in plasma and cardiac adipose tissue.
Asunto(s)
Adiponectina/metabolismo , Insuficiencia Cardíaca/fisiopatología , Infarto del Miocardio/complicaciones , Tejido Adiposo/metabolismo , Animales , Factor Natriurético Atrial/genética , Modelos Animales de Enfermedad , Insuficiencia Cardíaca/etiología , Ventrículos Cardíacos/metabolismo , Hemodinámica , Masculino , Peso Molecular , Péptido Natriurético Encefálico/genética , ARN Mensajero/metabolismo , Ratas , Ratas WistarRESUMEN
Orexin A (OxA), also known as hypocretin 1, is a regulatory neuropeptide involved in the control of various autonomic and neuroendocrine functions. It appears to have a significant impact on the regulation of trophic hormones secretion by influencing the hypothalamus and the pituitary. Orexin A acts through two types of receptor found in the pituitary. This suggests the possibility of direct action of OxA at the adenohypophysis level. The aim of this study was to investigate the direct effect of OxA on GnRH (gonadotrophin-releasing hormone)-stimulated LH and FSH secretion from cultured pituitary cells of sexually immature and mature female rats. Anterior pituitary cells obtained from immature and mature female rats (ovariectomized, and ovariectomized and treated with estradiol) were incubated with 10(-10)M or 10(-7)M orexin A for 1 hour and 4h and the effect on GnRH-stimulated (10(-9)M or 10(-6)M) LH and FSH release was examined. The concentrations of secreted gonadotrophins in the culture media were determined by RIA methods. Orexin A significantly inhibited GnRH-stimulated FSH release from pituitary cells isolated from immature female rats, whereas in cells of mature ovariectomized animals, the effect of OxA was dependent on the stimulatory dose of GnRH. When the cells were stimulated with a low dose of GnRH, orexin A inhibited the secretion of gonadotrophins, but when a high dose of GnRH was used, orexin A increased mainly the release of LH. In cultured pituitary cells from ovariectomized, estrogenized mature rats, orexin A inhibited the secretion of LH if the cells were stimulated with a high dose of GnRH. In conclusion, the results of this study revealed that orexin A may modify the sensitivity of gonadotrophic cells to GnRH, and its effect depends on the maturity and estrogen status of the rats from which the cells are isolated.
Asunto(s)
Hormona Liberadora de Gonadotropina/metabolismo , Péptidos y Proteínas de Señalización Intracelular/farmacología , Neuropéptidos/farmacología , Adenohipófisis/metabolismo , Animales , Células Cultivadas , Femenino , Hormona Folículo Estimulante/metabolismo , Hormona Luteinizante/metabolismo , Masculino , Orexinas , Ovariectomía , Adenohipófisis/efectos de los fármacos , Ratas , Ratas WistarRESUMEN
OBJECTIVES: To investigate the role of leptin, ghrelin, GH and IGF-1 in energy balance disturbances in Parkinson's disease (PD). MATERIALS AND METHODS: Thirty-nine patients were included: 11 PD patients with unintentional weight loss, 16 PD patients without weight loss and 12 controls. UPDRS, MMSE, MADRS, appetite scale, BMI, adipose tissue content, plasma leptin and active ghrelin concentrations and serum GH, IGF-1, TSH, T3 and T4, concentrations were evaluated. RESULTS: A lower plasma leptin concentration and a higher serum IGF-1 concentration were found in PD patients with weight loss. BMI and the content of adipose tissue were positively correlated with leptin concentration in all PD patients. Paradoxically, the lower BMI was, the lower plasma active ghrelin concentration was in PD patients with the weight loss. CONCLUSION: These findings confirm that changes of plasma leptin concentration occur in PD patients with loss of weight.
Asunto(s)
Metabolismo Energético/fisiología , Ghrelina/sangre , Leptina/sangre , Enfermedad de Parkinson/metabolismo , Pérdida de Peso , Tejido Adiposo/metabolismo , Anciano , Apetito/fisiología , Índice de Masa Corporal , Femenino , Hormona del Crecimiento/metabolismo , Humanos , Factor I del Crecimiento Similar a la Insulina/metabolismo , Masculino , Persona de Mediana Edad , Enfermedad de Parkinson/fisiopatología , Hormonas Tiroideas/metabolismo , Tirotropina/metabolismoRESUMEN
Cortistatin (CST), a novel neuropeptide, shows high structural homology and functional resemblance with somatostatin. CST binds with high affinity to all somatostatin receptors, and contrary to somatostatin, is also able to bind with MrgX2 and GH secretagogue receptor of ghrelin (GHS-R1) receptors. The aim of the present investigation was to evaluate in vivo the effect of peripheral administration of cortistatin on pituitary hormone release in comparison with somatostatin (SS) treatment. Adult male rats used in the experiment, were given peripheral injection of cortistatin, somatostatin or vehicle. Blood was withdrawn 60 and 120 minutes thereafter. We found short lasting significant decrease of GH concentration as a result of administration of CST and SS when compared with saline injected controls. Prolactin levels were increased 60 min after cortistatin but not to somatostatin injection. There was no effect of CST on both LH and FSH concentration; however, SS administration influenced gonadotropin secretion. We conclude that cortistatin play a regulatory role in pituitary secretion. Moreover, some differences have been found when compared cortistatin to somatostatin. Thus, when analyzing the mechanism of cortistatin activity it is worth to consider the effect of binding with receptors of somatostatin, specific receptor for CST (MrgX2) and GHS-R.
Asunto(s)
Hormona del Crecimiento/efectos de los fármacos , Neuropéptidos/farmacología , Prolactina/efectos de los fármacos , Animales , Hormona Folículo Estimulante/sangre , Hormona Folículo Estimulante/metabolismo , Hormona del Crecimiento/sangre , Hormona del Crecimiento/metabolismo , Hormona Luteinizante/sangre , Hormona Luteinizante/efectos de los fármacos , Hormona Luteinizante/metabolismo , Masculino , Prolactina/sangre , Prolactina/metabolismo , Radioinmunoensayo , Ratas , Ratas Endogámicas WKY , Somatostatina/farmacologíaRESUMEN
Neuropeptides play a pivotal role in the control of metabolic homeostasis. We aimed to evaluate the release of neuropeptides involved in the control of energy homeostasis in relation to metabolic status in aging humans. The study group consisted of 183 women: 75 centenarians (above 100 yrs old), 26 elderly women (below 70 yrs), 45 younger women (mean 26 yrs) and 37 obese women (mean 41.6 yrs). Fasting plasma concentration of leptin, adiponectin, ghrelin active, neuropeptide Y (NPY) and insulin were measured. Our results showed several differences in the metabolic and neurohormonal status in the centenarian group. The incidence of hypertension, glucose intolerance, insulin resistance and dyslipidemia was lower compared with obese women. Leptin and NPY concentrations were significantly lower than in elderly and obese subjects. Moreover, NPY level was higher than that in the younger group. Plasma adiponectin values were higher than in any of the other group. Insulin levels were significantly lower compared with the young and obese groups. Furthermore, a negative correlation was found between adiponectin and HOMA-IR, and adiponectin and insulin. Ghrelin active concentrations were significantly lower compared with the young subjects. However, ghrelin levels were higher than in obese subjects. We conclude that altered neuropeptide activity in centenarians may play a role in the mechanisms contributing to prolonged survival.
Asunto(s)
Envejecimiento/sangre , Neuropéptidos/sangre , Sistemas Neurosecretores/fisiología , Hormonas Peptídicas/sangre , Adiponectina/sangre , Adulto , Factores de Edad , Anciano , Anciano de 80 o más Años , Femenino , Ghrelina/sangre , Homeostasis/fisiología , Humanos , Insulina/sangre , Leptina/sangre , Longevidad/fisiología , Persona de Mediana Edad , Neuropéptido Y/sangre , Obesidad/sangreRESUMEN
The aim of the study was to determine, using the rat model, whether uterine infections cause an increase in cytokine concentrations in peripheral blood, and whether this increase is accompanied by changes in the pituitary-ovarian axis function. The levels of tumor necrosis factor-alpha, interleukin-1beta, luteinizing hormone, follicle-stimulating hormone, prolactin, progesterone, testosterone and estradiol-17beta in blood plasma as well as the weight of the uterus were determined after intrauterine infusion of lipopolysaccharide (15 microg), peptidoglycan (1 mg) and Escherichia coli (10(6) cfu) suspension on the day of metaestrus. On days 3, 7 and 10 after treatment the rats were sacrificed to collect the blood samples. Inflammation of uterus and vaginal discharge developed in all rats after treatment. The administration of lipopolysaccharide, peptidoglycan and Escherichia coli induced considerable changes in ovarian cyclic activity, mainly diestrus was observed. Application of all these factors resulted in an increase (P<0.05, P<0.01) of plasma levels of tumor necrosis factor-alpha, interleukin-1beta, mainly on day 3 and 7. In the rats receiving pathological factors, the plasma levels of luteinizing hormone, follicle-stimulating hormone, prolactin and estradiol-17beta decreased (P<0.05, P<0.01) whereas progesterone and testosterone increased (P<0.05). These results indicate that in rats, the developing inflammatory process of the uterus following lipopolysaccharide, peptidoglycan and Escherichia coli infusions is connected with an increase of tumor necrosis factor-alpha, interleukin-1beta concentrations in peripheral blood, and is accompanied by changes in the pituitary-ovarian axis function.
Asunto(s)
Citocinas/sangre , Hormonas/sangre , Inflamación/sangre , Inflamación/inducido químicamente , Animales , Escherichia coli/fisiología , Infecciones por Escherichia coli/sangre , Estradiol/sangre , Ciclo Estral , Femenino , Hormona Folículo Estimulante/sangre , Lipopolisacáridos/administración & dosificación , Hormona Luteinizante/sangre , Ovario/fisiología , Peptidoglicano/administración & dosificación , Hipófisis/metabolismo , Progesterona/sangre , Prolactina/sangre , Ratas , Ratas Wistar , Útero/anatomía & histología , Útero/citología , Excreción VaginalRESUMEN
OBJECTIVES: Some hormonal disturbances were demonstrated in starvation. Leptin, NPY and galanin play an important role in the control of appetite and in the mechanism of hormone release. METHODS: In order to evaluate the effect of starvation on the relationship between leptin, neuropeptide Y (NPY) galanin and pituitary and gonadal hormones release, plasma leptin, NPY and galanin as well as serum LH, FSH, prolactin (PRL), estradiol, progesterone levels in non-starved female rats (in diestrus) and after 72 hrs of starvation were measured with RIA methods. Effects of leptin, NPY and galanin administration on pituitary and gonadal hormones were investigated in vivo and in vitro experiments. RESULTS: Plasma leptin, NPY and galanin as well as serum estradiol and progesterone concentrations were significantly lower in starved rats as compared with non-starved rats. However serum prolactin level was significantly higher in starved rats. Opposite effects after leptin and NPY administration on hormone release in vivo and in vitro experiments were observed in non-starved rats. However, in starved rats we did not find changes in pituitary and gonadal hormones release after leptin, NPY and galanin injection or the hormonal response was blunted. CONCLUSIONS: 1) The disturbances in neuropeptides activity and in hormones release were observed in starvation. 2) Leptin, NPY and galanin have direct and indirect effects on pituitary and gonadal hormones release. 3) In starvation the hormonal response to leptin, NPY and galanin is impaired.
Asunto(s)
Hormonas/sangre , Neuropéptidos/sangre , Inanición/sangre , Animales , Regulación del Apetito/efectos de los fármacos , Regulación del Apetito/fisiología , Metabolismo Energético/efectos de los fármacos , Estradiol/sangre , Femenino , Hormona Folículo Estimulante/sangre , Galanina/sangre , Galanina/farmacología , Leptina/análisis , Leptina/farmacología , Hormona Luteinizante/sangre , Neuropéptido Y/sangre , Neuropéptido Y/farmacología , Progesterona/sangre , Prolactina/sangre , RatasRESUMEN
OBJECTIVES: It has been reported that leptin and neuropeptide Y (NPY) play a role in the control of appetite and in the regulation of hormonal secretion. METHODS: Plasma leptin, neuropeptide Y (NPY) and galanin concentrations were estimated in 13 women with bulimia nervosa (BN) 19 women with anorexia nervosa (AN) and in 19 healthy women of the control group (CG). RESULTS: Plasma leptin concentration in BN was significantly higher than that in AN and it was lower as compared with the control group, despite the same BMI (body mass index) in both the groups. Plasma leptin level in AN was significantly lower as compared with the controls. Plasma galanin concentrations in AN and BN did not differ significantly from the control group. Plasma NPY concentration in AN was lower than that in the control group. However, plasma NPY level in BN was significantly higher as compared with AN and with the control group (CG). The observed increase of NPY in BN was independent of BMI because BMI in bulimia nervosa was normal. CONCLUSIONS: The data may suggest that other factors than body weight changes may be involved in the modulation of leptin and NPY release in BN. The pathological behaviour of patients with bulimia nervosa may result from disturbed NPY release which is the strongest orexigenic factor.
Asunto(s)
Anorexia Nerviosa/sangre , Bulimia/sangre , Galanina/sangre , Leptina/sangre , Neuropéptido Y/sangre , Adolescente , Adulto , Índice de Masa Corporal , Femenino , Humanos , Valores de ReferenciaRESUMEN
OBJECTIVES: In many studies it has been reported, that leptin may play an important role not only in the regulation of food intake and body weight but can modify immune response. The aim of our study was to estimate the effects of the administration of exogenous leptin on serum concentration of proinflammatory cytokines (interleukin 6-IL 6 and tumor necrosis factor alpha-TNF alpha) and anti-inflammatory cytokine (interleukin 10 - IL 10) during LPS induced acute inflammation. We also estimated leptin's influence on pituitary, thyroid, adrenal and gonadal hormones in response to lipopolysaccharide (LPS) induced acute inflammation. METHODS: Male rats Wistar-Kyoto were divided into four groups, which received respectively: placebo (0.9% NaCl), LPS, leptin and leptin with LPS. The TNF alpha and IL 6 serum concentrations were measured after 2 hours and IL 10 after 4 hours. The pituitary, thyroid, adrenal and gonadal hormones serum concentrations were measured after 2 and 4 hours. Cytokine concentrations were estimated using ELISA tests and hormones concentrations using RIA tests. RESULTS: Leptin did not have an effect on both cytokine responses (proinflammatory and anti-inflammatory) in the time of LPS-induced acute inflammation. Leptin enhanced LPS-induced increasing of corticosterone secretion after 2 hours and decreased LPS-induced inhibition of testosterone secretion after 4 hours. CONCLUSIONS: Leptin can modulate hormone response during LPS-induced acute inflammation.
Asunto(s)
Hormonas/sangre , Inflamación/sangre , Inflamación/inmunología , Leptina/farmacología , Lipopolisacáridos/administración & dosificación , Animales , Corticosterona/sangre , Citocinas/sangre , Inflamación/inducido químicamente , Interleucina-10/sangre , Interleucina-6/sangre , Cinética , Leptina/administración & dosificación , Hormona Luteinizante/sangre , Masculino , Prolactina/sangre , Ratas , Ratas Endogámicas WKY , Testosterona/sangre , Tiroxina/sangre , Triyodotironina/sangre , Factor de Necrosis Tumoral alfa/análisisRESUMEN
BACKGROUND: Sex steroid hormones influence function of the human gastrointestinal tract. Although the specific receptor proteins have been identified in surgical specimens of both intestinal mucosa and colorectal carcinomas, it is still unknown whether they are expressed in intestinal epithelial cells. METHODS: Expression of androgen receptor (AR) protein and estrogen receptor (ER) protein was studied by Scatchard analysis and ELISA (for ER only) in surgical specimens of normal-appearing mucosa, colorectal carcinomas, isolated colonocytes, and human colorectal carcinoma cell lines. Northern analysis was applied to identify the appropriate mRNAs, followed by the sensitive technique of reverse transcription-polymerase-chain-reaction (RT-PCR). RESULTS: AR protein was identified in all surgical specimens analyzed and ER protein in 10 out of 13 normal-appearing mucosa specimens and 4 out of 7 colorectal carcinomas. The receptor proteins were not found in isolated colonocytes or in the transformed cell lines. RT-PCR confirmed that none of the isolated normal colonocytes or transformed colorectal carcinoma-derived cells expressed these mRNAs. Intestinal smooth muscle cells and fibroblasts were found to express sex steroid receptor mRNAs. CONCLUSIONS: Both receptors are present in human large intestine but are expressed in stromal cells and not in intestinal epithelial cells. We hypothesize that sex steroids may influence the function of colonocytes indirectly through stromal-epithelial interactions.
Asunto(s)
Neoplasias del Colon/química , Neoplasias Colorrectales/química , Receptores Androgénicos/metabolismo , Receptores de Estrógenos/metabolismo , Colon/química , Colon/citología , Ensayo de Inmunoadsorción Enzimática , Femenino , Humanos , Masculino , Reacción en Cadena de la Polimerasa , Receptores Androgénicos/genética , Receptores de Estrógenos/genética , Células del Estroma/metabolismo , Células Tumorales CultivadasRESUMEN
The effects of oestradiol and progesterone on LH-subunit mRNA levels were investigated in ovariectomized rats. Four weeks after ovariectomy, rats were implanted with silicone elastomer capsules containing oestradiol and/or injected daily with progesterone in oil (5 mg/rat) for 8 days. The levels of pituitary mRNA encoding alpha and LH-beta were determined using direct hybridization with specific [32P]cDNA probes. After oestradiol implantation in ovariectomized rats, both alpha and LH-beta mRNA decreased with time, with maximum inhibition after 6-8 days of treatment. Progesterone injected alone did not show any effect on alpha and LH-beta mRNA. Cytosolic progesterone receptors, determined using [3H]methyl-17 alpha-progesterone as ligand, were undetectable in control ovariectomized rats. In contrast, 2 days after oestradiol implantation, the number of receptors increased to 287.5 +/- 35.4 (S.E.M.) fmol/pituitary and reached a plateau of 400 +/- 21.8 fmol/pituitary after 4 days. The effects of progesterone were therefore examined by first implanting ovariectomized rats with oestradiol to induce progesterone receptors and then injecting progesterone daily for a further period of 6 days. As a result of this treatment, progesterone induced a decrease in the pituitary gland contents of both alpha and LH-beta mRNAs, and LH release was significantly greater than that observed in the group receiving oestradiol alone. Moreover, the mRNA levels in the animals treated with oestradiol plus progesterone were lower after 8 days of treatment than those observed in ovariectomized rats treated with a tenfold higher dose of oestradiol alone.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Estradiol/farmacología , Hormona Luteinizante/genética , Hipófisis/metabolismo , Progesterona/farmacología , ARN Mensajero/metabolismo , Animales , Sinergismo Farmacológico , Femenino , Hormona Luteinizante/sangre , Ovariectomía , ARN Mensajero/genética , Ratas , Ratas Endogámicas , Receptores de Progesterona/metabolismo , Factores de TiempoRESUMEN
Two different stressors footshocking and immobilization applied for 3 days induced in sheep differential behavioural and hormonal responses in cortisol and prolactin secretion. Immobilization drastically disturbed rumen motoric activity (significantly attenuated its contractions), caused loss of appetite and severe general depression. Footshocking did not induce any of these symptoms. Immobilization induced 2-3 fold higher rise of plasma cortisol mesors on the days of stressing as compared to footshocking. On the poststressing days after footshocking as well as after immobilization plasma cortisol mesors fell to 50% of the prestimulatory values. The rise of plasma prolactin mesors in footshocked and in immobilized animals on the days of stressing was nearly of the same magnitude. However, a significant difference in the response of prolactin secretion between footshocked and immobilized animals occurred in the circadian rhythmicity of the hormone secretion. Footshocking induced circadian rhythmicity with characteristic acrophases, while immobilization did not induce the circadian pattern of prolactin secretion. An attempt of interpretation of the described phenomena has been undertaken.
Asunto(s)
Conducta Animal/fisiología , Hidrocortisona/metabolismo , Prolactina/metabolismo , Estrés Fisiológico/fisiopatología , Animales , Ritmo Circadiano , Electrochoque , Femenino , Inmovilización , OvinosRESUMEN
The effect of 6-hydroxydopamine (6-OHDA) infusion into the third cerebral ventricle on the secretion pattern of prolactin in anoestrous sheep, subjected to repeated and prolonged stress-stimuli was followed. On the 12-15 th day after the infusion of 6-OHDA into the third cerebral ventricle and after having tested the effect of this infusion on plasma prolactin concentration, the animals were subjected to mild electric footshocks 9 hrs daily (9 a.m.-6 p.m.) for 3 consecutive days. Infusion of 6-OHDA induced a very high rise of plasma prolactin values by about 3 times as compared to those found before infusion (from 118.2 +/- 39.5 to 338.9 +/- 81.7 ng/ml mesor 24 h). On the other hand, the response of the animals pretreated with 6-OHDA to electric stimulation was characterized by the lack of changes in plasma prolactin concentration; their plasma hormone concentrations were neither raised during stimulation nor decreased after the stimulation and were maintained during all these days nearly at the same level as after the infusion of 6-OHDA. Central mechanisms which could account for the so high and prolonged elevation of plasma prolactin concentration after the infusion of 6-OHDA and for the lack of its rise under conditions of prolonged stress are discussed.
Asunto(s)
Hidroxidopaminas/farmacología , Prolactina/sangre , Estrés Fisiológico/fisiopatología , Anestro , Animales , Conducta Animal/efectos de los fármacos , Ritmo Circadiano , Electrochoque , Femenino , Hipotálamo/efectos de los fármacos , Hipotálamo/fisiología , Inyecciones Intraventriculares , Oxidopamina , OvinosRESUMEN
The effect of repeated and prolonged stress-stimuli applied during 3 days on the plasma prolactin concentration in sheep, in anoestrous, prooestrous and pregnant animals were studied. The following results were obtained: Repeated and prolonged weak electric stimuli applied in the form of footshocks in sheep during 3 days elicited a rise of mesor plasma concentration. The magnitude and the onset of this rise was not associated and dependent on the physiological state of animals. The mesor values of plasma prolactin concentration in all groups of animals except prooestrous ewes on the day following stimulation returned to their prestressing levels. Repeated and prolonged stimuli disturbed circadian rhythm of prolactin secretion existing only in prooestrous ewes, i.e. they caused its disappearance on the days during stimulation and its reappearance on the day following stimulation but at an accelerated and inverse time of the day to that found before stimulation. The induced rise of plasma prolactin concentration in anoestrous and pregnant ewes on the days during electric stimulation showed, according to Cosinor analysis, all features characteristic for acrophase of the circadian rhythm. This phenomenon may be considered as induced acrophase in stress condition.
Asunto(s)
Prolactina/sangre , Estrés Fisiológico/sangre , Anestro , Animales , Ritmo Circadiano , Electrochoque , Femenino , Embarazo , Proestro , OvinosRESUMEN
It has previously been observed that sheep subjected to repeated and prolonged stress stimuli showed biphasic cortisol responses. On the first and second day of stimulation an elevation was observed, while on the subsequent days and on the day after the stimulation a marked suppression of plasma cortisol level and a disappearance of its circadian rhythm was noted. It was hypothesized that these changes in the secretion of the hormone were caused by the alteration of catecholaminergic systems in the CNS. To verify this suggestion chemical lesions of the catecholergic systems of the diencephalon were carried out by the infusion of 6-hydroxydopamine (6-OHDA) into the third cerebral ventricle and animals treated in this fashion were subjected to repeated and prolonged electrical mild footshocking (applied during 3 days). The pretreated animals lost the circadian rhythm in cortisol secretion on the days before as well as during and after the electrical stimulation. The animals pretreated with 6-OHDA showed a significant rise of the plasma cortisol level during stimulation. This rise, as the highest daily concentration, occurring within about 1 h after the beginning of footshocking, was significantly accelerated in time with respect to the physiological acrophase, occurring in the early morning hours at the end of prestimulatory days. On the other hand, the pretreated animals did not show the decrease of plasma cortisol levels on the day after the stimulation, observed in normal non-pretreated ones.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Hidrocortisona/sangre , Hidroxidopaminas/administración & dosificación , Estrés Fisiológico/sangre , Animales , Conducta Animal/fisiología , Ritmo Circadiano , Estimulación Eléctrica , Femenino , Miembro Anterior/fisiología , Hipotálamo/efectos de los fármacos , Inyecciones Intraventriculares , Oxidopamina , Vehículos Farmacéuticos/farmacología , Ovinos , Estrés Fisiológico/fisiopatología , Factores de TiempoRESUMEN
Diurnal variations in the plasma cortisol level were studied in anoestrous, pro-oestrous and pregnant ewes subjected to weak electric stimulation of the fore-limbs 9 h daily for 3 consecutive days. In non-pregnant ewes the cortisol level rose on each of the 3 days when the stimulation was applied and then decreased on the day following the stimulation. A similar decrease in plasma cortisol concentrations in pregnant ewes appeared on the second day of footshocking. The acrophase of the circadian rhythm on electrostimulation days was synchronous with the time of application of footshocks; therefore, in stimulated ewes it was significantly accelerated compared to the prestimulatory day. A decrease in the plasma cortisol level in pro-oestrous and pregnant ewes was accompanied by disappearance of its normal rhythmicity. Since a normal plasma cortisol response to exogenous corticotrophin was noted after 3 days of footshocking it seems unlikely that the decrease in the cortisol level after prolonged stress was caused by exhaustion of the adrenal cortex. Some central mechanisms which could account for the biphasic changes in the plasma cortisol level and for disturbances of the hormone diurnal rhythmicity under conditions of prolonged stress are discussed.
Asunto(s)
Ritmo Circadiano , Hidrocortisona/sangre , Estrés Fisiológico/fisiopatología , Animales , Conducta Animal/fisiología , Estimulación Eléctrica , Estro , Femenino , Miembro Anterior/fisiología , Embarazo , Ovinos , Factores de TiempoRESUMEN
It has been demonstrated in our previous papers that in the anterior part of medial basal hypothalamus (AM BH) in sheep a stimulating, while in the caudal part of MBH (CMBH) an inhibiting centre of prolactin release are situated. These results suggested that CMBH might be the site of PIF production and prompted us to investigate the effect of dopamine (DA) on the concentration of prolactin in the peripheral blood (p.bl.) in animals in which CMBH had been previously lesioned and this concentration was very high. Microinfusion of L-dopamine into the third cerebral ventricle (c.v.) or into the internal maxillary artery in intact as well as in lesioned lactating ewes depressed distinctly the prolactin level in the p.bl. This action of DA suggests that in the CMBH exists dopaminergic system which itself plays an inhibitory role in the control of prolactin release without involvement of PIF.