摘要:

AbstractPituitary‐adrenal responses to stress in the neonatal rat have been reported to be substantially reduced compared to older animals (i.e. a stress hyporesponsive period). This supposed period of endocrine quiescence is characterized by reduced stress‐induced increases in both plasma ACTH and corticosterone. At the same time a number of authors have noted the decreased plasma corticosteroid‐binding globulin (CBG) levels of the neonate, and there is evidence for an increased percentage of free corticosterone as well as age‐related changes in the volume of distribution for corticosterone. These findings suggest that the reduced CBG levels might enhance the biological significance of existing glucocorticoid levels, beyond that assumed on the basis of plasma total corticosterone levels. We examined this question by estimating hippocampal glucocorticoid receptor occupancy and ‘translocation’ in Day 6, Day 15, and adult animals under basal and stressful conditions. The results showed that: 1) plasma ACTH levels were elevated in Day 6 animals in response to acute exposure to ether, maternal separation, and maternal separation + ether, however, ACTH responses were substantially lower than in Day 15 or adult animals; 2) Plasma total corticosterone levels followed a similar pattern; most noteworthy was the potent glucocorticoid response in Day 15 animals to the combination of maternal separation + ether; 3) Plasma CBG levels in Day 6 animals were extremely low (<3% adult values); by Day 15 CBG levels were about 25% of adult levels. Interestingly, maternal separation was associated with a substantial decrease in plasma CBG levels; 4) Hippocampal glucocorticoid receptor occupancy/translocation was similar at all ages under both basal and stress conditions. The only notable exception occurred during maternal separation in Day 15 animals, where the percentage of hippocampal glucocorticoid receptor occupancy/translocation was higher than that observed at any time in either Day 6 or adult animals. This finding is likely related to the decrease in plasma CBG that occurs following separation of Day 15 pups from the dam.Thus, despite the higher corticosterone level in the adult, the increase in glucocorticoid receptor occupancy/translocation was generally comparable across all ages either under basal conditions, or following stress. These receptor data underscore the importance of developmental changes in plasma

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1996.tb00680.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractWe recently reported that galanin gene expression is markedly increased in the hyperplastic anterior pituitary gland of the human growth hormone‐releasing hormone (hGHRH) transgenic mouse. To determine if another pituitary peptide hormone with putative growth‐promoting activity is similarly affected, or if this effect is specific to the peptide galanin, we examined vasoactive intestinal polypeptide (VIP) gene expression in the hypothalamic‐pituitary axis of male hGHRH transgenic and non‐transgenic mice. The objectives were to: 1) assess VIP peptide concentrations, 2) estimate relative differences in VIP mRNA levels, 3) determine the effects of acute treatment with 17(3‐estradiol on VIP peptide and mRNA levels, and 4) quantify the density of immunoreactive VIP pituitary cells by immunohistochemistry. Four to five month old male hGHRH transgenic mice and their non‐transgenic siblings were identified by PCR. Immunoreactive VIP concentrations were decreased by 50% in the anterior pituitary glands of hGHRH transgenic mice as compared to non‐transgenic siblings. In contrast, no differences in immunoreactive VIP concentrations were observed in the hypothalamus or frontal cerebral cortex of transgenic and non‐transgenic mice. Treatment with 17β‐estradiol significantly increased VIP concentrations in the anterior pituitary gland of both transgenic and non‐transgenic mice; however, VIP peptide concentrations in the anterior pituitary glands of hGHRH transgenic mice remained 50% lower. Relative differences in VIP mRNA levels were estimated by RT‐PCR, and were found to be 2.5‐fold higher in the anterior pituitary glands of non‐transgenic mice. In contrast, no differences in VIP mRNA levels in the cerebral cortex were detected between transgenic and non‐transgenic mice. Treatment with 17(3‐estradiol increased VIP mRNA levels in the anterior pituitary, but not in the cerebral cortex. In concert with the changes in VIP peptide and mRNA, the density of immunoreactive VIP pituitary cells was decreased approximately 50% in hGHRH transgenic mice. In conclusion, unlike galanin gene expression, VIP peptide and mRNA levels are significantly decreased in the anterior pituitary gland of hGHRH transgenic mice. Moreover, these changes appear to be tissue‐specific and are likely due, in part, to the decrease in the density of VIP‐containing pituitary cells in the hyperplastic pituitary. Although the pituitary cell type(s) synthesizing VIP remains unclear, these data suggest that VIP in the anterior pituitary is not stimulating pituitary tumor de

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1996.tb00681.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractImmunolabeling of cryo‐sections of human anterior pituitaries obtained at autopsy, and of cryo‐sections of freshly prepared rat anterior pituitaries, with a panel of monoclonal antibodies against markers of the monocyte/dendritic cell/macrophage lineage, reveals in both species a characteristic pattern of immunopositive cells, among which many cells with dendritic phenotype are found. Cells characterized by marker expression of MHC‐class II determinants and a dendritic morphology are present in both human and rat anterior pituitary. Markers characteristic of dendritic cells such as the L25 antigen and the OX6 antigen were present in anterior pituitaries from human and rat respectively. The population of MHC‐class II expressing dendritic cells of the rat anterior pituitary is compared at the ultrastructural level with the folliculo‐stellate cell population, which cell type has been previously characterized by its distinctive ultrastructure and immunopositivity for the S100 protein. Using immuno‐electron microscopy of rat anterior pituitaries fixed with periodate‐lysine‐paraformaldehyde, we were able to distinguish non‐granulated cells expressing MHC‐class II determinants, whereas no MHC‐class II expression was found in the granulated endocrine cells. Using double immunolabeling of cryo‐sections of these rat AP with 25 nm and 15 nm gold labels, we demonstrated an overlap between the populations of MHC‐class II‐expressing and S100 protein‐expressing cells. Furthermore, MHC‐class II‐expressing and S100‐positive cells showed ultrastructural characteristics that have been previously ascribed to folliculo‐stellate cells. At the light microscopical level in the rat AP, a proportion of 10 to 20% of the S100‐positive cells was found immunopositive for the MHC‐class II marker OX6. In the human AP, S100‐positive folliculo‐stellate cells and cells expressing the leukocyte common antigen CD45 were found to occupy predominantly different tissue compartments in the human anterior pituitary, namely the epithelial parenchyme cords and perivascular compartments respectively. A proportion of CD45+cells was found in the parenchyme compartment and, vice versa, indicating an overlap of the tissue compartments in which both cell types occur. However, at the light microscopical level we could not find cells expressing both the S100 and CD45 marker. The present finding of a proportion of S100‐positive pituitary cells with ultrastructural and immunohistochemical characteristics of both dendritic cells and folliculo‐stellate cells, confirms the suggested heterogeneity of the latter cell group with respect to their ultrastructural phenotype and putative function. The possibility of a myeloid origin of part of the folliculo‐stellate cell group in the AP, is discussed and might elucidate some of the discrepancies in the literature con

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1996.tb00682.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractBrain microdialysis is a method commonly exploited by neuropharmacologists to study the mechanism of action and preclinical features of centrally acting drugs. It allows measurement of chemical messengers released into the extracellular space, providing a first approximation of neuronal function in selected areas.In this study we have applied the microdialysis of the hypothalamus to evaluate the release of somatostatin from neurosecretory neurons which are involved in growth hormone regulation and validated this method with different challenges.

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1996.tb00683.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractExtracellular single unit activity was recorded from 73 neurones in the median preoptic nucleus (MnPO), identified by antidromic activation as projecting to the supraoptic nucleus (SON) area in urethane‐anaesthetized male rats. Thirteen of 73 identified MnPO neurones were silent, and 44 of 60 spontaneously active MnPO neurones were tested for their responses to electrical stimulation of the nucleus tractus solitarius (NTS). The cells were divided into 4 groups according to their responses; those which were excited orthodromically (OD+; n = 15), those which were unresponsive (UN; n = 21), those which were inhibited orthodromically (OD−; n=4), those which showed initial inhibition followed by excitation (OD+n = 4). Some of these neurones were further tested for their responses to haemorrhage and/or increase in blood pressure produced by intravenous administration of the oe‐agonist, phenylephrine, and/or to hyperosmotic stimulation produced by intraperitoneal injection of 1.5 M NaCl. Six out of 10 OD+cells were excited by haemorrhage, 6 out of 11 OD+cells were inhibited by phenylephrine, and 5 out of 9 OD+cells were excited by hypertonic saline. On the other hand the UN cells tended to be unresponsive to each type of stimulus. Three out of 7 OD+cells were excited by both haemorrhage and hypertonic saline, and 3 out of 8 OD+cells were inhibited by phenylephrine and excited by hypertonic saline. The results may suggest that MnPO neurones which receive afferent input from the NTS may be sensitive not only to haemodynamic change but also to change in plasma osmotic pressure and that such population of MnPO neurones may integrate a part of the haemodynamic and osmotic information and contribute to the control of neurohypophysial hormone re

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1996.tb00684.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe anteroventral periventricular nucleus of the preoptic region (AVPV) represents a key site for hormonal feedback on gonadotropin secretion. It plays a critical role in the neural control of luteinizing hormone secretion and contains high densities of neurons that express receptors for estrogen and progesterone. In this studyin situhybridization was used to examine the expression of mRNAs encoding the estrogen (ER) and progesterone (PR) receptors in the AVPV during the estrous cycle. ER gene expression fluctuated during the cycle with the lowest levels of ER mRNA observed in animals killed on the afternoon of proestrus, and the highest levels present in animals killed during metestrus. This apparent inverse relationship between circulating levels of estradiol (E2) and ER mRNA levels in AVPV neurons was supported by the observation that treatment of ovariectomized rats with E2 suppressed expression of ER mRNA in the AVPV. The influence of progesterone (P4) on ER expression was less pronounced, but a significant increase in ER mRNA in the AVPV was detected 3 h after treatment with P4. In contrast, PR mRNA levels were highest in the AVPV during diestrus and lowest on the morning of proestrus suggesting that PR expression in the AVPV is regulated in a complex manner that may reflect the combined regulatory effects of E2 and P4. E2 treatment caused a dramatic induction of PR mRNA in the AVPV, but P4 did not affect PR mRNA expression acutely, although PR mRNA appears to be attenuated in the AVPV 27 h after P4 treatment. These findings suggest that ovarian steroid hormones regulate ER and PR gene expression in the AVPV during the estrous cycle, which may represent molecular events that contribute to cyclic changes in the responsiveness of AVPV neurons to steroid hormones.

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1996.tb00685.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractMelanin concentrating hormone (MCH) is a 19 amino‐acid peptide expressed in high concentrations within the dorso‐lateral hypothalamus of rats, sheep and man. MCH regulates skin colour and ACTH release in teleost fish, however, its physiological relevance in mammals is unclear. The present study examined the cardiovascular and metabolic actions of intracerebroventricular (i.e.v.) infusion of MCH, and the pro‐MCH derived peptide Neuropeptide‐E‐I (NEI), in conscious, chronically instrumented sheep. Human MCH (1–19) or NEI (1–13) was infused i.e.v. for 24 h into 6 sheep, and measurements were made every 10 min of arterial pressure, heart rate, cardiac output, stroke volume and peripheral blood flow/conductance. Recordings of water intake (H2Oin), urine volume (Uv), urinary Na (UNaV) and K excretion (UKV) were made, as well as hematocrit, plasma Na, K, osmolality, protein, glucose, ACTH, vasopressin, renin, endothelin, ANF, Cortisol and aldosterone concentrations. After 24 h of infusion at 10 μg/h, MCH produced a significant increase in Uv from 0.8 ± 0.2 to 1.4 ± 0.3 l/day, together with an increase in UNaV from 56 ± 8 to 107 ± 14 mmol/day, and in UKV from 202 ± 18 to 369 ± 38 mmol/day. H2Oin was unchanged. Similar renal changes were observed during i.e.v. infusion of NEI. There was no change in any cardiovascular parameter, although hematocrit showed a large decrease with infusion of both peptides after 24 h infusion. Plasma osmolality increased from 291 ±1 to 295 ± 1 mOsm/kg during MCH infusion, whereas total protein and plasma Na and K were unchanged. MCH increased plasma glucose from 3.4 ± 0.2 to 3.8 ± 0.2 mmol/l. Plasma aldosterone exhibited a 30–40% decrease following MCH or NEI infusion, whereas all other plasma concentrations remained unchanged. This study has shown that i.c.v. infusion of MCH or NEI can produce diuretic, natriuretic and kaliuretic changes in conscious sheep, triggered by a possible increase in plasma volume as indicated by the changes in hematocrit. These results, together with anatomical data reporting the presence of MCH/NEI in fluid regulatory areas of the brain, indicate that MCH/NEI may be an important peptide involved in the central control of fl

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1996.tb00686.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractWe compared sympathoadrenal responses to intermittent cold (SART) stress (in which cold exposure is interrupted by 4‐hourly intervals daily at room temperature) with those to continuous cold (−3°C) stress. Plasma levels of dihydroxyphenylalanine (DOPA), catecholamines and their metabolites as well as tyrosine hydroxylase (TH) activities in sympathetically innervated tissues were examined in rats exposed to each stressor for 1 day or for 5 days. Neither SART nor continuous exposure to cold for 1 day or 5 days altered plasma epinephrine (EPI) levels. However, norepinephrine (NE) and dihydroxyphenylglycol (DHPG) levels increased markedly during exposure to these stressors. On the first day of SART or continuous cold stress, NE levels were increased similarly, but the increments in DHPG levels were greater during SART stress. Since DHPG is formed in neurons, neural reuptake of NE may be more enhanced on the first day of SART stress than on the first day of continuous cold stress. After 5 days of SART stress plasma NE levels were significantly higher than those found after 5 days of continuous cold exposure. Plasma levels of DHPG were elevated to the same extent in both 5 days SART‐ and continuously cold‐stressed rats, whereas plasma levels of methoxyhydroxyphenylglycol (MHPG) increased only by 5 days SART stress. Even at 1 h after the removal from 5 days SART stress, increased plasma levels of NE, DHPG and MHPG were still evident. These results suggest that 5 days SART stress elevates extraneuronal O‐methylation of DHPG, and that NE turnover is more greatly increased by SART stress than by continuous cold stress. Plasma levels of DOPA, dopamine, dihydroxyphenylacetic acid and homovanillic acid also increased after either SART or continuous cold stress for 1 day and 5 days. Adrenal TH activities were significantly increased in rats exposed to SART or continuous cold stress for 1 day and 5 days, but in brown fat TH activity was elevated only in rats exposed to 5 days of continuous cold. Both SART and continuous cold stress are selective and potent stimuli for activation of the sympathoneural system, apparently without significant adrenomedullary EPI release. The increase of TH activity in the brown fat pad as well as of plasma NE and its metabolites is probably a result of adaptation to cold. It appears that even short intervals of return to a normal environmental temperature, as in SART, are sufficient to diminish sympathetic adaptati

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1996.tb00687.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe present study has used a rat neuronal nitric oxide synthase (nNOS) antibody to examine the relationship of nNOS immunoreactivity to GnRH neurons in the ovariectomized and intact diestrous and proestrous rat. A striking band of nNOS‐immunoreactive cells was identified in the rostral preoptic area which began in the median preoptic nucleus and organum vasculosum of the lamina terminalis and formed an inverted Y‐type distribution above the rostral third ventricle at the level of the anteroventral periventricular nucleus. Another band of nNOS‐immunoreactivity was found extending through the internal zone of the median eminence into the arcuate nucleus. Although nNOS immunoreactivity was not detected within GnRH neuronal cell bodies in any of the experimental groups, GnRH perikarya located in the rostral preoptic area, but not elsewhere, were found to be surrounded by nNOS‐containing cells. In the median eminence, nNOS and GnRH immunoreactivities were distributed separately in the internal and external zones, respectively.These results provide evidence that, regardless of their pattern of activity, GnRH neurons in the female rat do not express nNOS. Instead, a close anatomical relationship between nNOS‐immunoreactive cells and GnRH perikarya and fibers has been identified within specific sub‐regions of the rostral preoptic area and in the median eminence. Such findings are compatible with a role for NO at both sites in regulating the release of GnRH throughout the es

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1996.tb00688.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1996.tb00689.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY