scholarly journals Agouti yellow mutation increases adrenal response to ACTH in mice

2004 ◽  
pp. 265-270 ◽  
Author(s):  
NM Bazhan ◽  
AY Shevchenko ◽  
NR Karkaeva ◽  
TV Yakovleva ◽  
EN Makarova
Keyword(s):  
Hpa Axis ◽  
Feedback Inhibition ◽  
Plasma Concentrations ◽  
Plasma Corticosterone ◽  
Agouti Protein ◽  
Basal Plasma ◽  
Agouti Related Protein ◽  
Design And Methods ◽  
Hpa Function

OBJECTIVE: Agouti protein (AP) and agouti-related protein with a similar sequence and action are endogenous antagonists of melanocortin receptors, implicated in the control of the hypothalamo-pituitary-adrenal (HPA) axis. Dominant mutation of the agouti gene (agouti yellow (A(y))) in heterozygous A(y)/a mice leads to ectopic overexpression of AP and produces an obese phenotype. The existing data on the HPA function in A(y)/a-mice are equivocal; therefore, the present study aimed to assess HPA function in 3-month-old male C57Bl/6J mice of two agouti genotypes: A(y)/a (ectopic AP overexpression) and a/a (absence of AP). DESIGN AND METHODS: In order to evaluate the HPA function, activating (15-min restriction, ACTH-induced corticosterone production in vitro) and inhibiting (i.p. injection of dexamethasone, 0.02 microg/g body weight) stimuli were employed. To estimate the effect of obesity on some HPA functions, A(y)/a males were subdivided into obese and non-obese groups. RESULTS: Basal plasma concentrations of ACTH and corticosterone; basal corticosterone production in vitro; and feedback inhibition of resting corticosterone levels by dexamethasone were similar in A(y)/a- and a/a-mice. Restraint-induced plasma corticosterone was greater in obese and non-obese A(y)/a-mice than in a/a-mice, whereas restraint-induced plasma ACTH levels were similar. Adrenal cell responses to ACTH (10(-13)-10(-10) M) were higher in obese and non-obese A(y)/a-mice than in a/a-mice. Dexamethasone, injected 3 h prior to stress, inhibited stress-induced corticosterone levels by a significantly greater amount in A(y)/a-mice than in a/a-mice. CONCLUSIONS: AP may have both stimulating and inhibiting influences on the HPA axis. AP overproduction increased the response of the HPA to short-restraint stress due to increased adrenal responsiveness to ACTH; this result was not effected by obesity development.

Changes in the hypothalamic contents of LHRH-I and -II and in pituitary responsiveness to synthetic chicken LHRH-I and -II during the progesterone-induced surge of LH in the laying hen

1990 ◽  
Vol 127 (3) ◽  
pp. 487-496 ◽  
Author(s):  
S. C. Wilson ◽  
R. A. Chairil ◽  
F. J. Cunningham ◽  
R. T. Gladwell
Keyword(s):  
Plasma Concentration ◽  
Pituitary Gland ◽  
Laying Hens ◽  
Plasma Concentrations ◽  
Posterior Hypothalamus ◽  
Anterior Hypothalamus ◽  
Significant Fall ◽  
Basal Plasma

ABSTRACT The contents of LHRH-I and -II in the anterior hypothalamus and posterior hypothalamus (including the mediobasal hypothalamus and median eminence) were measured at 90, 180 and 360 min after the i.m. injection of laying hens with progesterone. Whilst no changes were observed in the content of LHRH-I in the anterior hypothalamus, LHRH-I in the posterior hypothalamus tended to fall at 90 and 180 min after injection of progesterone in hens maintained on 16 h light:8 h darkness (16L:8D) and 8L:16D respectively. Pretreatment of laying hens with tamoxifen significantly increased the hypothalamic contents of LHRH-I and -II, raised the basal plasma concentration of LH and modified the LH response to progesterone injection. In hens in which tamoxifen prevented an increase in the plasma concentration of LH after progesterone injection, the content of LHRH-I in the posterior hypothalamus remained unchanged. In contrast, in hens in which progesterone stimulated a steep increase in LH within 90 min, there was a pronounced and significant fall in LHRH-I content of the posterior hypothalamus. No change in the hypothalamic content of LHRH-II was observed during the progesterone-induced surge of LH until plasma concentrations had attained maximal values or started to decline. Then, in hens maintained on 16L:8D, a significant fall in the content of LHRH-II in the anterior hypothalamus was found at both 180 and 360 min after injection with progesterone. Tests in vitro and in vivo of the responsiveness of the pituitary gland to synthetic LHRH-I and -II revealed no change at 90 min after injection of laying hens with progesterone, when plasma concentrations of LH were increasing, but a pronounced reduction when plasma LH concentrations were maximal or falling. These results suggest that LHRH-I mediates in the progesterone-induced increase in the plasma concentration of LH. Although the subsequent decline in plasma LH was associated with a reduced responsiveness of the pituitary gland to LHRH, a significant correlation between the contents of LHRH-I and -II in the anterior hypothalamus and a fall in the hypothalamic content of LHRH-II when plasma LH was maximal or declining allows the possibility of an involvement of this peptide in the neuroendocrine events preceding ovulation. Journal of Endocrinology (1990) 127, 487–496

Differential activation of the pituitary-adrenocortical axis after stress in the rat: use of two genetically selected lines (Roman low- and high-avoidance rats) as a model

1989 ◽  
Vol 123 (3) ◽  
pp. 477-485 ◽  
Author(s):  
C.-D. Walker ◽  
R. W. Rivest ◽  
M. J. Meaney ◽  
M. L. Aubert
Keyword(s):  
Glucocorticoid Receptor ◽  
Conditioned Avoidance ◽  
Plasma Corticosterone ◽  
Type I ◽  
Pituitary Cells ◽  
Acth Secretion ◽  
Rapid Acquisition ◽  
Basal Plasma

ABSTRACT We have examined the activation of the pituitary-adrenal axis in two lines of rats, the Roman high (RHA)- and low (RLA)-avoidance rats known to be emotionally different. These rats are selected for rapid acquisition of a conditioned avoidance response (RHA) compared with failure to acquire this response (RLA). In this study the endocrine response (ACTH, corticosterone, aldosterone) of RLA and RHA rats to two types of stress was examined: exposure to openfield stress for 10 min (Op) or exposure to ether vapours for 3 min (E). Basal plasma ACTH concentrations were lower in RLA than in RHA rats (RLA: 110·8 ± 24·5 ng/l; RHA: 252·7 ± 60·8 ng/l, P<0·05) but the absolute values of ACTH reached after both types of stress were comparable between RLA and RHA rats. Plasma corticosterone and aldosterone under resting conditions were not different between RLA and RHA rats. Plasma corticosterone was higher in RLA following openfield stress (P<0·05) while no differences between RLA and RHA were observed after ether stress (RHA: basal = 66±14·nmol/l, Op =384± 55, E= 606± 75; RLA: basal=121±52, Op = 612 ±92, E= 698 ± 89). Stressinduced increases in plasma aldosterone were higher in the RLA line after both types of stress (RHA: basal = 175±36 pmol/l, Op = 546±53, E= 563± 47; RLA: basal = 272 ± 64, Op =1246 ± 91, E= 863 ± 72). Pituitary responsiveness to exogenous corticotrophinreleasing factor (CRF) in vivo and in vitro differed in the two lines: administration of ovine CRF (10 μg/kg body weight, i.p.) resulted in significant increases in ACTH secretion but the response was significantly lower in RHA rats (RHA: 511·1 ±41·5 ng/l; RLA: 831·4 ± 70·3 ng/l, P<0·01). Dispersed pituitary cells from the RHA line exhibited a smaller response to CRF (10 nmol/l) treatment in vitro compared with cells derived from the RLA rats (RHA: 750 ± 83% of control; RLA: 1374 ±79, P<0·01) suggesting differences in pituitary sensitivity to CRF between the two lines. Additional differences at the pituitary level were observed since the type II glucocorticoid receptor population in RHA rats was higher than in RLA rats (RHA: 246±13 fmol [3H]RU28362 bound/mg protein; RLA: 173±18, P<0·01). Similarly, hippocampal type I glucocorticoid receptor population was increased in RHA rats (RHA: 172·2 ± 8·3 fmol [3H]aldosterone bound/mg protein; RLA: 116·7±7·3, P< 0·01). It is concluded that first, differences in pituitary activity between RLA and RHA rats are distinct from changes observed at the adrenal level, secondly, increased stress-induced ACTH output in the RLA line is associated with enhanced pituitary sensitivity to CRF and possibly with diminished corticosterone inhibitory feedback action on CRF and ACTH secretion, and thirdly, the possible involvement of differences in the pattern of CRF secretion between RLA and RHA rats on resting pituitary ACTH secretion cannot be excluded. Journal of Endocrinology (1989) 123, 477–485

Relative occupation of type-I and type-II corticosteroid receptors in rat brain following stress and dexamethasone treatment: functional implications

1987 ◽  
Vol 115 (3) ◽  
pp. 459-467 ◽  
Author(s):  
J. M. H. M. Reul ◽  
F. R. van den Bosch ◽  
E. R. de Kloet
Keyword(s):  
Rat Brain ◽  
Plasma Concentrations ◽  
Striking Difference ◽  
Classical Type ◽  
Type I ◽  
Type Ii ◽  
Binding Studies ◽  
Receptor Sites ◽  
Basal Plasma

ABSTRACT The rat brain contains two receptor systems for corticosterone: the type-I corticosterone-preferring receptor and the classical type-II glucocorticoid receptor. The two receptor populations can be distinguished in binding studies with the 'pure' synthetic glucocorticoid 11β,17β-dihydroxy-6-methyl-17α (1-propynyl)-androsta-1,4,6-trione-3-one (RU 28362). In-vitro autoradiography and quantitative image analysis showed that the type-I receptor was localized almost exclusively in the hippocampus, whereas the type-II receptor extended throughout the brain, with the highest levels in the nucleus paraventricularis, nucleus supraopticus and in the thalamic, amygdaloid, hippocampal and septal regions. Unoccupied type-I and type-II receptor sites, as measured in vitro by cytosol binding of 3H-labelled steroids, displayed a large difference in the rate of appearance after adrenalectomy. The availability of type-I receptors exhibited a marked increase, reaching maximal levels within 4–7 h, and then remained constant until 2 weeks after adrenalectomy. The availability of type-II receptors did not change considerably during the first 24 h after adrenalectomy, but displayed a large increase in capacity during the subsequent 2 weeks. After adrenocortical activation as a consequence of exposure to a novel environment, plasma concentrations of corticosterone increased to reach a peak of 811 nmol/l after 30 min and attained the basal concentration (43 nmol/l) after 240 min. During this time, occupation of type-I receptors increased from 77·8% at 0 min to 97% at 30–60 min and then declined to 84·8% after 240 min. Occupation of the type-II receptors was 28·1% at 0 min, 74·5% after 30 min and 32·8% after 240 min. Injection of dexamethasone (25 μg/100 g body wt) at 08.00 h resulted in suppression of basal plasma concentrations of corticosterone and prevented the circadian-driven rise in circulating corticosterone. Occupation of type-I receptors did not change considerably as a result of injection of dexamethasone, but occupation of type-II receptors was markedly increased till 16.00 h compared with that after injection of vehicle. It was concluded that the type-I and type-II receptors are not only localized differently in the rat brain, but also exhibit a striking difference in occupation after manipulation of the pituitary-adrenocortical system. The data further support the concept of a type-I receptor-mediated tonic activating influence and a type-II receptor-mediated feedback action of corticosterone on brain function. J. Endocr. (1987) 115, 459–467

scholarly journals Paraventricular Nucleus Administration of Calcitonin Gene-Related Peptide Inhibits Food Intake and Stimulates the Hypothalamo-Pituitary-Adrenal Axis

Endocrinology ◽  
2003 ◽  
Vol 144 (4) ◽  
pp. 1420-1425 ◽  
Author(s):  
Waljit S. Dhillo ◽  
Caroline J. Small ◽  
Preeti H. Jethwa ◽  
Sabina H. Russell ◽  
James V. Gardiner ◽  
...  
Keyword(s):  
Food Intake ◽  
Hpa Axis ◽  
Male Rats ◽  
Mrna Levels ◽  
Related Protein ◽  
Melanocyte Stimulating Hormone ◽  
Calcitonin Gene ◽  
Agouti Related Protein ◽  
Prior Administration

Abstract Calcitonin gene-related protein (CGRP) inhibits food intake and stimulates the hypothalamo-pituitary-adrenal (HPA) axis after intracerebroventricular injection in rats. However, the hypothalamic site and mechanism of action are unknown. We investigated the effects of intraparaventricular nucleus administration (iPVN) of CGRP on food intake and the HPA axis in rats and the effect of CGRP on the release of hypothalamic neuropeptides in vitro. In addition, we investigated the effects of food deprivation on hypothalamic CGRP expression. CGRP dose-dependently reduced food intake in the first hour after iPVN injection in fasted male rats (saline, 5.1 ± 0.8 g; 0.3 nmol CGRP, 1.1 ± 0.5 g; P &lt; 0.001 vs. saline). iPVN injection of CGRP8–37 (a CGRP1 receptor antagonist) alone had no effect on food intake. However, the reduction in food intake by iPVN CGRP was attenuated by prior administration of CGRP8–37 [CGRP8–37 (10 nmol)/CGRP (0.3 nmol), 3.0 ± 0.8 g; P &lt; 0.05 vs. 0.3 nmol CGRP]. CGRP (100 nm) stimulated the release of α-melanocyte stimulating hormone, cocaine- and amphetamine-related transcript, corticotropin-releasing hormone, and arginine vasopressin from hypothalamic explants to 127 ± 19%, 148 ± 10%, 158 ± 17%, and 198 ± 21% of basal levels, respectively (P &lt; 0.05 vs. basal), but did not alter the release of either neuropeptide Y or agouti-related protein. Hypothalamic CGRP mRNA levels in 24-h fasted rats were increased to 130 ± 8% of control levels [CGRP mRNA (arbitrary units), 4.75 ± 0.4; controls, 3.65 ± 0.34; P &lt; 0.05]. Our data suggest that CGRP administered to the PVN inhibits food intake and stimulates the HPA axis.

Corticosteroids mediate fast feedback of the rat hypothalamic-pituitary-adrenal axis via the mineralocorticoid receptor

2008 ◽  
Vol 294 (6) ◽  
pp. E1011-E1022 ◽  
Author(s):  
Helen C. Atkinson ◽  
Susan A. Wood ◽  
Emma S. Castrique ◽  
Yvonne M. Kershaw ◽  
Crispin C. R. Wiles ◽  
...  
Keyword(s):  
Receptor Antagonist ◽  
Hpa Axis ◽  
Mineralocorticoid Receptor ◽  
Feedback Inhibition ◽  
Inhibitory Effect ◽  
Plasma Corticosterone ◽  
Time Of Day ◽  
Sampling System ◽  
Mineralocorticoid Receptor Antagonist ◽  
Hypothalamic Pituitary Adrenal

The aim of this study was to investigate fast corticosteroid feedback of the hypothalamic-pituitary-adrenal (HPA) axis under basal conditions, in particular the role of the mineralocorticoid receptor. Blood samples were collected every 5 min from conscious rats at the diurnal peak, using an automated blood sampling system, and assayed for corticosterone. Feedback inhibition by rapidly increasing concentrations of ligand was achieved with an intravenous bolus of exogenous corticosteroid. This resulted in a significant reduction in plasma corticosterone concentrations within 23 min of the aldosterone bolus and 28 min of methylprednisolone. Evaluation of the pulsatile secretion of corticosterone revealed that the secretory event in progress at the time of administration of exogenous steroid was unaffected, whereas the next secretory event was inhibited by both aldosterone and methylprednisolone. The inhibitory effect of aldosterone was limited in duration (1 secretory event only), whereas that of methylprednisolone persisted for 4–5 h. Intravenous administration of canrenoate (a mineralocorticoid receptor antagonist) also had rapid effects on the HPA axis, with an elevation of ACTH within 10 min and corticosterone within 20 min. The inhibitory effect of aldosterone was unaffected by pretreatment with the glucocorticoid receptor antagonist RU-38486 but blocked by the canrenoate. These data imply an important role for the mineralocorticoid receptor in fast feedback of basal HPA activity and suggest that mineralocorticoids can dynamically regulate basal corticosterone concentrations during the diurnal peak, a time of day when there is already a high level of occupancy of the cytoplasmic mineralocorticoid receptor.

scholarly journals BDNF Overexpression in the Prelimbic Cortex Does Not Reduce Anxiety- and Depression-like Behavior in Serotonin Knockout Rats

2020 ◽  
Author(s):  
Danielle M. Diniz ◽  
Kari Bosch ◽  
Francesca Calabrese ◽  
Paola Brivio ◽  
Marco A. Riva ◽  
...  
Keyword(s):  
Hpa Axis ◽  
Selective Serotonin Reuptake Inhibitors ◽  
Depressive Disorders ◽  
Forced Swim Test ◽  
Plasma Corticosterone ◽  
Anxiety And Depression ◽  
Prelimbic Cortex ◽  
Forced Swim ◽  
Basal Plasma ◽  
The Brain

AbstractDepressive disorders are one of the leading causes of non-fatal health loss in the last decade. Adding to the burden, the available treatments not always properly work for some individuals. There is, therefore, a constant effort from clinical and preclinical studies to bring forward a better understanding of the disease and look for novel alternative therapies. Two target systems very well explored are the serotonin and the brain-derived neurotrophic factor (BDNF) systems. Selective serotonin reuptake inhibitors (SSRIs), a commonly used class of antidepressants, target the serotonin transporter (SERT) and increase serotonin levels, which in turn also leads to an increase in BDNF. A rat model lacking SERT (SERT knockout) has been a useful tool to study the interplay between serotonin and BDNF. SERT−/− rats present increased extracellular levels of serotonin, yet BDNF levels are decreased, especially in the prefrontal cortex (PFC) and hippocampus. The animals further display anxiety- and depression-like behavior. Therefore, BDNF might mediate the phenotype expressed by the SERT−/− rats. In this study, we sought to investigate whether overexpression of BDNF in the brain of SERT−/− rats would rescue its anxious and depressive-like behavior. Through stereotaxic surgery, SERT−/− and wild-type (WT) rats received BDNF or GFP lentivirus microinfusions into the prelimbic cortex subregion of the mPFC and were submitted to the sucrose consumption, open field test, and forced swim tests. Additionally, we measured hypothalamus-pituitary-adrenal (HPA)-axis reactivity. The results revealed that SERT−/− rats presented decreased sucrose intake, decreased locomotor activity, and increased escape-oriented behavior in the forced swim test compared to WT rats. BDNF upregulation in WT rats caused alterations in the HPA-axis function, resulting in elevated basal plasma corticosterone levels and decreased plasma corticosterone upon stress. In conclusion, BDNF overexpression in the PrL, in general, did not rescue SERT−/− rats from its depression- and anxiety-like behavior, and in WT animals, it caused a malfunction in the HPA-axis.

OVARIAN AND ADRENAL STEROIDS DURING PREGNANCY AND THE OESTROUS CYCLE IN THE RAT

1977 ◽  
Vol 74 (1) ◽  
pp. 89-98 ◽  
Author(s):  
T. F. OGLE ◽  
J. I. KITAY
Keyword(s):  
Adrenal Gland ◽  
Mating Behaviour ◽  
Plasma Concentrations ◽  
Plasma Corticosterone ◽  
Oestrous Cycle ◽  
Coefficient Of Determination ◽  
Adrenocortical Function ◽  
Metabolic Clearance

Changes in adrenocortical function of the rat during the 4-day oestrous cycle and pregnancy were studied in vivo and in vitro. Regulation of adrenal production of progesterone and corticosterone was of particular interest. Morning (09.00 h) plasma concentrations of corticosterone were similar at each phase of the cycle, but a higher concentration was found in the afternoon (15.00 h pro-oestrus). However, the rate of progesterone utilization for corticosterone production by adrenal homogenates was essentially unchanged at all periods of the cycle. Therefore, the activities of the 21- and 11β-hydroxylating systems appeared not to be important determinants of plasma corticosterone levels (coefficient of determination (r2) = 0·06). These results indicate that adrenal secretion of progesterone is not specifically regulated during the cycle. On the other hand, resting plasma levels of corticosterone declined by 80–85% from the value on the morning of pro-oestrus between days 5 and 12 of pregnancy and then increased on day 22 and after parturition. These fluctuations did not result from alterations in the rate of metabolic clearance but rather, were closely coupled to the capacity of adrenal tissue to convert progesterone to corticosterone (r2 = 0·87). These findings suggest that progesterone utilization may be specifically curtailed at the expense of corticosterone production at days 5 and 12 of pregnancy. Concurrent measurements of adrenal venous progesterone and ovarian venous progesterone (under stressful conditions) showed that the adrenal gland secretes 2–10 times more progesterone than the ovary at all stages of the oestrous cycle, on day 22 of pregnancy, and on the first day of lactation. Thus, the adrenal gland is capable of secreting large amounts of progesterone which, if present at the appropriate time, may inhibit, delay or facilitate ovulation and onset of mating behaviour as described by other workers. Under such circumstances, however, progesterone secretion appears not to be specifically regulated but seems instead to be due to precursor spillover, since the proportionate secretion of corticosterone does not change.

scholarly journals The vagus nerve is critical for regulation of hypothalamic-pituitary-adrenal axis responses to acute stress

2021 ◽  
Author(s):  
Bailey N Keller ◽  
Angela E Snyder ◽  
Caitlin R Coker ◽  
Elizabeth A Aguilar ◽  
Mary K O'Brien ◽  
...  
Keyword(s):  
Vagus Nerve ◽  
Hpa Axis ◽  
Restraint Stress ◽  
Acute Stress ◽  
Plasma Corticosterone ◽  
Action Potential Firing ◽  
Acute Restraint Stress ◽  
Potential Firing ◽  
Crf Neurons ◽  
Hpa Function

The hypothalamic pituitary adrenal (HPA) axis is a critical regulator of physiologic and psychological responses to acute and chronic stressors. HPA axis function is control by numerous feedback inhibitory mechanisms, disruptions of which can lead to various psychiatric conditions, such as depression, posttraumatic stress disorder, and schizophrenia. Vagus nerve stimulation has been shown to be efficacious in these various mental health issues potentially via modulation of HPA axis function, but the mechanisms by which the vagus nerve may regulate HPA function has not been fully elucidated. In the present studies, we sought to test the hypothesis that the vagus nerve is a critical regulator of HPA function. Neuroendocrine function and neurocircuit changes in corticotropin releasing factor (CRF) neurons in the paraventricular nucleus of the hypothalamus (PVN) was examined following acute stress after subdiaphragmatic left vagotomy (VX) in adult male Sprague-Dawley rats. We found that VX mimics HPA activation seen in sham surgery animals exposed to acute restraint stress, particularly increased plasma corticosterone levels, elevated PVN CRF mRNA, and increased action potential firing of putative CRF neurons in PVN brain slices. Furthermore, VX animals exposed to acute restraint stress showed increased elevations of plasma corticosterone and PVN CRF mRNA which may be due to lack of compensatory PVN GABAergic signaling in response to acute stress. Both Sham/Stress and VX/no stress conditions increases action potential firing in putative PVN CRF neurons, but this effect was not seen in the VX/stress condition, suggesting that not all forms of stress compensation are lost following VX. Overall, these findings suggest that the vagus nerve may play a critical role in regulating HPA axis function via modulation of local PVN neurocircuit activity.

scholarly journals Relaxin-3 stimulates the neuro-endocrine stress axis via corticotrophin-releasing hormone

2014 ◽  
Vol 221 (2) ◽  
pp. 337-346 ◽  
Author(s):  
B M McGowan ◽  
J S Minnion ◽  
K G Murphy ◽  
D Roy ◽  
S A Stanley ◽  
...  
Keyword(s):  
Hpa Axis ◽  
Reproductive Function ◽  
Plasma Corticosterone ◽  
Stress Axis ◽  
Central Administration ◽  
Appetite Control ◽  
Plasma Acth ◽  
Releasing Hormone

Relaxin-3 is a member of the insulin superfamily. It is expressed in the nucleus incertus of the brainstem, which has projections to the hypothalamus. Relaxin-3 binds with high affinity to RXFP1 and RXFP3. RXFP3 is expressed within the hypothalamic paraventricular nucleus (PVN), an area central to the stress response. The physiological function of relaxin-3 is unknown but previous work suggests a role in appetite control, stimulation of the hypothalamic–pituitary–gonadal axis and stress. Central administration of relaxin-3 induces c-fos expression in the PVN and increases plasma ACTH levels in rats. The aim of this study was to investigate the effect of central administration of human relaxin-3 (H3) on the hypothalamic–pituitary–adrenal (HPA) axis in male rodentsin vivoandin vitro. Intracerebroventricular (i.c.v) administration of H3 (5 nmol) significantly increased plasma corticosterone at 30 min following injection compared with vehicle. Intra-PVN administration of H3 (1.8–1620 pmol) significantly increased plasma ACTH at 1620 pmol H3 and corticosterone at 180–1620 pmol H3 at 30 min following injection compared with vehicle. The stress hormone prolactin was also significantly raised at 15 min post-injection compared with vehicle. Treatment of hypothalamic explants with H3 (10–1000 nM) stimulated the release of corticotrophin-releasing hormone (CRH) and arginine vasopressin (AVP), but H3 had no effect on the release of ACTH fromin vitropituitary fragments. These results suggest that relaxin-3 may regulate the HPA axis, via hypothalamic CRH and AVP neurons. Relaxin-3 may act as a central signal linking nutritional status, reproductive function and stress.

scholarly journals Hypothalamic-Pituitary-Adrenal Axis Hyporesponsiveness to Restraint Stress in Mice Deficient for Large-Conductance Calcium- and Voltage-Activated Potassium (BK) Channels

Endocrinology ◽  
2007 ◽  
Vol 148 (11) ◽  
pp. 5496-5506 ◽  
Author(s):  
Paula J. Brunton ◽  
Matthias Sausbier ◽  
Georg Wietzorrek ◽  
Ulrike Sausbier ◽  
Hans-Guenther Knaus ◽  
...  
Keyword(s):  
Hpa Axis ◽  
Anterior Pituitary ◽  
Restraint Stress ◽  
Plasma Concentrations ◽  
Bk Channels ◽  
Patch Clamp Recording ◽  
Hypothalamic Pituitary Adrenal ◽  
Neurosecretory Neurons

Stress activates the hypothalamic-pituitary-adrenal (HPA) axis, releasing ACTH from the anterior pituitary gland and glucocorticoids from the adrenal cortex. Stress also activates the sympathetic nervous system, evoking adrenaline release from the adrenal medulla. Large-conductance calcium- and voltage-activated potassium (BK) channels have been implicated in regulation of cellular excitability in these systems. Here, we examine the functional role of BK channels in HPA axis regulation in vivo using female mice genetically deficient (BK−/−) for the pore-forming subunits of BK channels. BK−/− phenotype in the HPA was confirmed by immunohistochemistry, Western blot analysis, and corticotrope patch-clamp recording. Restraint stress-induced plasma concentrations of ACTH and corticosterone were significantly blunted in BK−/− mice compared with wild type (WT) controls. This stress hyporesponsiveness was associated with reduced activation of hypothalamic paraventricular nucleus (PVN) neurons. Basal expression of CRH, but not arginine vasopressin mRNA in the PVN was significantly lower in BK−/− mice compared with WT controls. Total anterior pituitary ACTH peptide content, but not proopiomelanocortin mRNA expression or corticotrope number, was significantly reduced in BK−/− mice compared with WT. However, anterior pituitary corticotropes from BK−/− mice fully supported ACTH output, releasing a significantly greater proportion of stored ACTH in response to secretagogue in vitro compared with WT. These results support an important role for BK channels in both the neural circuitry and endocrine output of the HPA axis and indicate that the stress hyporesponsiveness in BK−/− mice primarily results from reduced activation of hypothalamic PVN neurosecretory neurons.

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