Increase In ACTH Research Articles

276 Prenatal Exposure to Dexamethasone Permanently Alters the Expression of 11Beta HSD1, Mineralcorticoid and 5HT1B Receptor in Rat Hippocampus

Changes in gene expression in the brain, pituitary, and adrenal have been reported in a number of prenatal stress studies. However, it is not clear whether the high maternal glucocorticoid (GC) level is directly responsible for these perturbations. We exposed rat dams to DEX during gestation days 14–19 and found a significant decrease in birth weight and adult weight of the male offspring. In addition, this treatment elicited a significant increase in serum ACTH and CORT. In contrast, circulating levels of serotonin were significantly lower in the DEX-exposed adult males. Using real time RT-PCR we measured a significant decrease in the hippocampal mineralcorticoid receptor (MR) and serotonin receptor, 5-HT1B. In contrast, the mRNA levels measured for hippocampal 5-HT1A, 5-HT2A, and glucocorticoid receptor (GR) were not significantly different from the control animals. Interestingly, males exposed to DEX in utero exhibited a significant increase in hippocampal 11 beta hydroxysteroid dehydrogenase 1 (11beta HSDI). Unlike the placental 11beta HSD2 isozyme which inactivates endogenous CORT, hippocampal 11beta HSD1 regenerates active corticosterone from inert 11dehydrocorticosterone. It is becoming increasingly apparent that glucocorticoid actions are not only mediated via intracellular GR and MR, but by the presence of 11beta HSDI and its capacity for regulating intracellular concentration of active GC. HPA axis hyperactivity may result, in part, from a reduced hippocampal tonic inhibition. It is possible that the significant changes in hippocampal corticosteroid receptor and 11beta HSD I gene expression contribute to this loss of inhibition. Moreover, since 5HT receptors in the rat hippocampus are normally under tonic inhibition by corticosteroid, the elevation of both circulating and intracellular CORT would suppress the serotonergic system in this region. These data demonstrate that exposure to DEX in utero has persistent effects on the adult brain thus supporting the prenatal origin of adult dysfunction hypothesis.

The Role of Calcitonin Gene-Related Peptide in the in Vivo Pituitary-Adrenocortical Response to Acute Hypoxemia in the Late-Gestation Sheep Fetus

This study tested the hypothesis that calcitonin gene-related peptide (CGRP) has a role in mediating the in vivo fetal adrenal glucocorticoid response to acute stress. The hypothesis was tested by investigating the effects of fetal treatment with a selective CGRP antagonist on plasma ACTH and cortisol responses to acute hypoxemia in the late-gestation sheep fetus. Under anesthesia, six fetuses at 0.8 of gestation were surgically instrumented with vascular catheters. Five days later, fetuses were subjected to 0.5-h hypoxemia during treatment with either iv saline or a CGRP antagonist, in randomized order, on different days. Treatment started 30 min before hypoxemia and ran continuously until the end of the challenge. Arterial blood samples were collected for plasma ACTH and cortisol measurements (RIA) and blood gas monitoring. CGRP antagonism did not alter basal arterial blood gas or endocrine status. During hypoxemia, similar falls in arterial partial pressure of oxygen occurred in all fetuses. During saline infusion, acute hypoxemia induced significant increases in fetal ACTH and cortisol concentrations. During CGRP antagonism, the pituitary-adrenal responses were markedly attenuated. Correlation of paired plasma ACTH and cortisol values from all individual fetuses during normoxia and hypoxemia showed positive linear relationships; however, neither the slope nor the intercept of the peptide-steroid relationship was affected by CGRP antagonism. These data support the hypothesis that CGRP is involved in the in vivo regulation of fetal adrenocortical steroidogenesis during acute hypoxemia. In addition, the data reveal that CGRP may have a role in the control of other components of the hypothalamo-pituitary-adrenal axis during stimulated conditions in fetal life.

Physiological and behavioral responses to interleukin-1β and LPS in vagotomized mice

It is well established that peripheral administration of interleukin-1 (IL-1) and lipopolysaccharide (LPS) can activate the hypothalamo-pituitary-adrenocortical (HPA) axis, alter brain catecholamine and indoleamine metabolism, and affect behavior. However, the mechanisms of these effects are not fully understood. Stimulation of afferents of the vagus nerve has been implicated in the induction of Fos in the brain, changes in body temperature, brain norepinephrine, and some behavioral responses. In the present study, the IL-1β- and LPS-induced changes in certain behaviors, HPA axis activation, and catecholamine and indoleamine metabolism were studied in mice following subdiaphragmatic vagotomy. IL-1β and LPS induced the expected decreases in sweetened milk, food intake, and locomotor activity, and the responses to IL-1β, but not LPS, were slightly attenuated in vagotomized mice. Subdiaphragmatic vagotomy also attenuated the IL-1β- and LPS-induced increases in plasma ACTH and corticosterone, but the attenuations of the responses to IL-1β were only marginally significant. There were also slight reductions in the responses in catecholamine and serotonin metabolism, and the increases in brain tryptophan in several brain regions. These results indicate that the vagus nerve is not the major pathway by which abdominal IL-1β and LPS effect behavioral, HPA and brain catecholamine and indoleamine responses in the mouse. These results resemble those we observed in subdiaphragmatically vagotomized rats, but in that species the subdiaphragmatic vagotomy markedly attenuated the ACTH and corticosterone responses, and prevented the hypothalamic noradrenergic activation, as well as the fever. Overall the results indicate that the various responses to peripheral IL-1 and LPS involve multiple mechanisms including vagal afferents, and that there are species differences in the relative importance of the various mechanisms.

Suppression of the HPA axis stress-response: implications for relapse.

This article presents the proceedings of a symposium held at the meeting of the International Society for Biomedical Research on Alcoholism (ISBRA) in Mannheim, Germany, in October 2004. This symposium explored the potential role of hypothalamic-pituitary-adrenal (HPA) axis dysregulation upon relapse. HPA axis stimulation induces the release of the glucocorticoid cortisol, a compound with profound effects upon behavior and emotion. Altered stress-responses of the HPA axis in abstinent alcohol-dependent subjects, therefore, may influence their affective and behavioral regulation, thus impacting their potential for relapse. Bryon Adinoff began the symposium with a review of HPA axis dysfunction in alcohol-dependent subjects, including recent studies from his lab demonstrating an attenuated glucocorticoid response to both endogenous and exogenous stimulation in one-month abstinent men. Klaus Junghanns presented his work demonstrating that a blunted ACTH or cortisol response to subjective stressors (social stressor or alcohol exposure) is predictive of a return to early drinking. The final two presenters examined the interaction between naltrexone and HPA responsiveness in alcohol-dependent or at-risk subjects, as naltrexone induces an increase in ACTH and cortisol. Falk Kiefer discussed the relationship between basal HPA axis responsivity and clinical outcome following treatment with naltrexone or acamprosate. Plasma ACTH significantly decreased over the course of the study in the placebo group, but not the medication groups [corrected] Lower basal concentrations of ACTH and cortisol were associated with quicker relapse in the placebo group only. Suchitra Krishnan-Sarin described her preliminary work, in which family-history positive (FH+) and family history negative (FH-) subjects were administered naltrexone, followed by an assessment of alcohol-induced craving. The cortisol response to alcohol was significantly and inversely related to craving in the FH+, but not the FH-, subjects. Alterations in HPA axis responsivity may therefore have a negative impact upon clinical outcome in alcohol-dependent subjects, and disinhibition of the axis with medication may have therapeutic potential.

Hypothalamic-pituitary disconnection in fetal sheep blocks the peripartum increases in adrenal responsiveness and adrenal ACTH receptor expression

Although it has been recognized for over a decade that hypothalamic-pituitary disconnection (HPD) in fetal sheep prevents the late gestation rise in plasma cortisol concentrations, the underlying mechanisms remain unclear. We hypothesized that reductions in adrenal responsiveness and ACTH receptor (ACTH-R) expression may be mediating factors. HPD or sham surgery was performed at 120 days of gestation, and catheters were placed for blood sampling. At approximately 138 days of gestation, fetuses were killed, and adrenals were removed for cell culture and analyses of ACTH-R mRNA and protein. After 48 h, adrenocortical cells were stimulated with ACTH for 2 h, and the medium was collected for cortisol measurement. The same cells were incubated overnight with medium or medium containing ACTH or forskolin (FSK), followed by ACTH stimulation (as above) and cortisol and cellular ACTH-R mRNA analyses. HPD prevented the late gestation increase in plasma cortisol and bioactive ACTH and reduced adrenal ACTH-R mRNA and protein levels by over 35%. HPD cells secreted significantly less cortisol than sham cells (3.2 +/- 1.2 vs. 47.3 +/- 11.1 ng.ml(-1).2 h(-1)) after the initial ACTH stimulation. Overnight incubation of HPD cells with ACTH or FSK restored cortisol responses to acute stimulation to levels seen in sham cells initially. ACTH-R mRNA levels in cells isolated from HPD fetuses were decreased by over 60%, whereas overnight incubation with ACTH or FSK increased levels by approximately twofold. Our findings indicate that the absence of the cortisol surge in HPD fetuses is a consequence, at least in part, of decreased ACTH-R expression and adrenal responsiveness.

Local anaesthetics attenuates spinal nociception and HPA-axis activation during experimental laparotomy in pigs

The effect of local anaesthetics on spinal nociception and activation of the hypothalamic–pituitary–adrenal axis (HPA-axis) was examined in a porcine model of abdominal surgery. A standardised laparotomy without visceral involvement was performed on 24 pigs. One group received a unilateral infiltration of mixed lidocaine and bupivacaine in skin, muscle and peritoneum of the surgical area prior to surgery ( n = 12), while local anaesthetics were replaced by isotonic saline in a second group ( n = 12). A sham group was subjected to anaesthesia ( n = 8), but did not undergo surgery. Two hours after surgery, half of the pigs from each group were perfused with formalin and the spinal cord was taken out for stereological quantification of the total number of Fos-like-immunoreactive (Fos-LI) neurones in the dorsal horn. Surgery with saline gave rise to a significant increase in the number of Fos-LI neurones ipsilaterally (107,001 ± 16,548; p < 0.001) as well as contralaterally (12,766 ± 3,842; p < 0.01) compared to the sham group. In animals undergoing surgery with LA, the number of Fos-LI neurones ipsilaterally was not significantly different from the sham group ( p = 0.78), and was reduced significantly both ipsilaterally (6960 ± 1662; p < 0.001) and contralaterally (3974 ± 1131; p < 0.05) compared to the saline group. In the other half of each group, blood samples, for determination of ACTH, cortisol, C-reactive protein and interleukin-6 concentrations, were drawn prior to and at predetermined time-points during and after surgery. Surgery with saline gave rise to dramatic increases in plasma ACTH and cortisol ( p < 0.01 and p < 0.001, respectively) within 15 min of incision. In contrast, no changes from the initial concentrations of ACTH and cortisol were observed in pigs receiving local anaesthetics. No changes in plasma concentrations of C-reactive protein or interleukin-6 were observed in either of the groups. These results indicate that spinal nociception and HPA-axis activation caused by laparotomy in pigs can be attenuated by use of infiltration and incisional local anaesthetics prior to surgery. The present model provides a valuable tool in the evaluation of analgesic treatment during surgery, offering objective measures of both nociception and stress.

Chronic subcutaneous leptin infusion diminishes the responsiveness of the hypothalamic–pituitary–adrenal (HPA) axis in female rhesus monkeys

The fat derived protein leptin has its anorexic action through a number of neuropeptides including an upregulation of corticotropin releasing hormone (CRH) expression in the hypothalamus. However, the influence of leptin on these neuropeptides may be different during stress. The present study used ovariectomized female rhesus monkeys ( n=8) to further define the effect of leptin on HPA responsivity. To accomplish this, we assessed the effects of constant leptin infusion on cortisol and ACTH secretion in both a predictable and unpredictable situation as well as in response to dexamethasone suppression–CRH stimulation test. We hypothesized that leptin would attenuate the increase in cortisol and ACTH to a novel, unpredictable situation and would enhance glucocorticoid negative feedback and diminish the response to CRH. Animals were assessed under control placebo conditions and during a 28 day infusion with recombinant human leptin (6 μg/kg/day, SC). Within each treatment condition, HPA responsivity was assessed during no estradiol replacement and acute estradiol replacement that produced serum concentrations of approximately 40 pg/ml. However, the results indicated that neither estradiol alone or in combination with leptin had any consistent effect on the outcome measures. Compared to the control condition, leptin had no effect on the cortisol diurnal rhythm; however, evening but not morning plasma ACTH concentrations were significantly lower during leptin infusion. In contrast, the response in plasma cortisol and ACTH to an unpredictable situation was significantly attenuated by chronic leptin infusion. Furthermore, leptin enhanced glucocorticoid negative feedback and blunted CRH-induced increase in both cortisol and ACTH. Taken together, these data suggest that in the female monkey, leptin has little effect on basal cortisol. However, when the HPA axis is activated, leptin attenuates the neuroendocrine response by enhancing glucocorticoid negative feedback. These data underscore the potential importance of leptin in maintaining homeostasis through its diverse interaction with the HPA axis.

Hormonal and metabolic responses to acute ghrelin administration in patients with bulimia nervosa

Ghrelin is generally influenced by energy balance status and is inversely associated with body mass index (BMI), being reduced in simple obesity, notable exception being Prader Willi syndrome, and elevated in several conditions of undernutrition, including anorexia nervosa (AN). Interestingly, ghrelin levels have also been found elevated in patients with bulimia nervosa (BN) in spite of normal BMI. In humans, intravenous (iv) ghrelin administration induces endocrine (increase in GH, PRL, ACTH and cortisol) and metabolic (increase in glucose and decrease in insulin) effects as well as an increase in appetite and food intake. In AN, ghrelin administration surprisingly leads to a decreased GH response and absence of glycemic variations but normal PRL, ACTH and insulin response. This pattern would reflect a decrease in sensitivity to ghrelin or, alternatively, the metabolic status of AN. To further clarify the function of ghrelin in eating disorders, the endocrine and metabolic response to acute iv ghrelin (1.0 microg/kg) was studied in seven young women with purging BN (BW, BMI, mean+/-SEM: 20.3+/-0.5 kg/m2). Circulating total ghrelin levels were also measured. The results in BW were compared to those recorded in a group of nine healthy women (HW; BMI 22.3+/-2.5 kg/m2). The GH response to ghrelin in BW overlapped with that in HW. Ghrelin administration also led to a similar increase in PRL, ACTH, cortisol and glucose levels in the two groups. Insulin levels were not significantly modified by ghrelin administration in either group. The overlapping endocrine and metabolic response to ghrelin in the two groups occurred with regard to circulating total ghrelin levels which were higher in BW than in HW. In conclusion, BN, a condition of ghrelin hypersecretion, is connoted by a normal endocrine and metabolic response to exogenous ghrelin administration.

Pharmacodynamic effects of opiate receptor antagonism: An agonist challenge study

Background Pharmacodynamic effects of opiate antagonists and agonists such as naltrexone (NTX) and fentanyl (FE) have been documented in separate studies and various populations. However, no data are available for a direct comparison in the same group of subjects. Methods NTX 50mg QD and a matched placebo were compared in a randomized double-blind crossover study conducted in a research hospital setting. NTX was administered for 3 days to 16 healthy males. ACTH, cortisol, FSH, LH, PRL and pupillary diameter (PD) were measured on Day 1. On Day 3, blockade of agonist-induced effects was tested by use of an IV bolus of FE. Results On Day 1, NTX induced an increase in LH, ACTH and cortisol (p<0.01 each; 90%CI ratio[1.29–1.91],[1.42–2.40],[1.26–2.06]). No effect was observed on FSH, PRL and PD. On Day 3, NTX was associated with a blockade of the following FE effects: increase in ACTH (p<0.0001,[0.15–0.59]), cortisol (p=0.01,[0.38–0.81]) and PRL (p<0.0001,[0.12–0.22]) and reduction in PD (p<0.0001,[2.47–3.32]). NTX did not influence pain perception during the cold pressor test performed after FE. Conclusion Blockade of FE-induced changes in PRL and PD were the most significant treatment effects observed. In contrast to FE-induced decreases in ACTH/cortisol reported in stressed or surgical patients, an increase was observed in healthy volunteers. This effect was blocked by NTX. Clinical Pharmacology & Therapeutics (2005) 77, P28–P28; doi: 10.1016/j.clpt.2004.11.110

Time Course of Vasopressin and Oxytocin Secretion after Stress in Adrenalectomized Rats

To characterize the participation of vasopressin (AVP) and oxytocin (OT) in hypothalamus-pituitary-adrenal regulation after adrenalectomy (ADX), we evaluated corticosterone, ACTH, AVP and OT plasma concentrations and AVP and OT content of the paraventricular nucleus (PVN) at different periods (3 h, 1, 3, 7 and 14 days) in sham or ADX rats under basal conditions and after immobilization stress. ADX animals showed undetectable corticosterone levels, while sham animals showed a marked increase in corticosterone and ACTH 3 h after surgery, then lowering to basal control levels. ADX rats showed high basal ACTH levels with a triphasic response without changes after immobilization. After three hours, the ADX group showed higher OT levels than the sham group. OT was increased after immobilization stress in sham and ADX groups. AVP plasma levels did not change throughout the basal or stress studies in either group. There was a decrease in hypothalamic AVP content 1 and 3 days after ADX under basal and stress conditions. Plasma osmolality showed a significant decrease in the ADX group at 3, 7, and 14 days. In conclusion, there are different pituitary-adrenal axis set points after removal of the glucocorticoid negative feedback. The role of vasopressinergic and oxytocinergic neurons in the ACTH secretion after ADX or immobilization stress appears to differ. Magnocellular AVP is unlikely to contribute to ACTH secretion in response to ADX or immobilization stress. On the other hand, OT is elicited by immobilization stress and might contribute to the ACTH secretion during short-term ADX.

Preserved inhibitory effect of recurrent hypoglycaemia on the male gonadotrophic axis

Hypoglycaemia-induced decreases in male LH and testosterone concentrations are possibly mediated by activation of the hypothalamus-pituitary-adrenal (HPA) axis or by an increase in PRL. As counterregulatory stress hormone release is attenuated during recurrent hypoglycaemia, we questioned whether the gonadotrophic axis and PRL adapt similarly. We performed two consecutive hypoglycaemic clamps on day 1 and one clamp on the following day in 15 healthy men. Blood concentrations of gonadotrophins, PRL, testosterone, ACTH and cortisol were measured during the first and the third clamp, taking place at the same time of day. During hypoglycaemia, serum concentrations of LH and testosterone decreased (P < 0.003 for both), PRL, ACTH and cortisol increased (P < 0.001), and FSH remained unchanged (P = 0.90). The hypoglycaemia-induced decreases in LH and testosterone concentrations were similar during the first and the last clamp (P > 0.28 for both) whereas the increase in PRL, ACTH and cortisol was markedly attenuated during the third clamp (P < 0.001). LH and testosterone responses do not adapt to recurrent hypoglycaemia, whereas the increase in PRL is attenuated, indicating adaptation. Considering the marked decrease in the responses of PRL and the HPA axis after antecedent hypoglycaemia, the data suggest that the hypoglycaemia-induced decreases in LH and testosterone concentrations, not adapting to recurrent hypoglycaemia, are mediated independently, probably by blood glucose itself.

Differential behavioral and neuroendocrine effects of repeated nicotine in adolescent and adult rats

Despite the high prevalence of tobacco abuse among adolescents, the neurobiology of nicotine addiction has been studied mainly in adult animals. Repeated administration of this drug to adult rats induces behavioral sensitization. Nicotine activates the HPA axis in adult rats as measured by drug-induced increases in ACTH and corticosterone. Both behavioral sensitization and corticosterone are implicated in drug addiction. We examined the expression of behavioral sensitization induced by nicotine as well as the changes in corticosterone levels after repeated injections of nicotine in adolescent and adult animals. Adolescent and adult rats received subcutaneous (s.c.) injections of saline or 0.4 mg/kg of nicotine once daily for 7 days. Three days after the last injection animals were challenged with saline or nicotine (0.4 mg/kg; s.c.). Nicotine-induced locomotion was recorded in an activity cage. Trunk blood samples were collected in a subset of adolescent and adult rats and plasma corticosterone levels were determined by radioimmunoassay. Adult, but not adolescent, rats expressed behavioral sensitization. Pretreatment with nicotine abolished corticosterone-activating effect of this drug only in adult animals, indicating the development of tolerance at this age. Our results provide evidence that adolescent rats exposed to repeated nicotine display behavioral and neuroendocrine adaptations distinct from that observed in adult animals.

The HPA axis response to stress in women: effects of aging and fitness

This study tested the hypotheses that aging is associated with greater hypothalamic-pituitary-adrenal (HPA) axis reactivity to psychological stress, and whether aerobic fitness is associated with a lower HPA axis response to psychological stress. Three groups, consisting of young-unfit women (27.9+/-2.5 yr, n=10), older-unfit women (66.3+/-1.4 yr, n=14), and older-fit women (66.6+/-2.0 yr, n=12), underwent the Matt Stress Reactivity Protocol (MSRP). The MSRP is a stress test battery that combines mental challenges, a physical challenge, and a psychosocial stressor. Definition of fitness was based on maximal oxygen consumption (VO(2max)) where unfit was defined as having VO(2max)</=average for the respective age group and fit was defined as VO(2max)>average for the respective age group. The MSRP elicited increases in heart rate, blood pressure, ACTH, and cortisol (P<0.001). The older-unfit women had significantly greater cortisol responses to the challenge than both the young-unfit and the older-fit women (P<0.05), who did not differ from each other. ACTH levels were significantly higher in the older-unfit women at baseline and throughout the trial, compared to both young-unfit and the older-fit (P<0.01). The ACTH response was not different between any of the groups. The young-unfit women had greater heart rate responses than the older-unfit (P<0.01), while the latter had greater systolic blood pressure responses (P<0.01). There were no significant differences between the older-unfit and older-fit in terms of heart rate or blood pressure responses. Our result shows that among unfit women, aging is associated with greater HPA axis reactivity to psychological stress, and that higher aerobic fitness among older women can attenuate these age-related changes as indicated by a blunted cortisol response to psychological stress. These findings suggest that exercise training may be an effective way of modifying some of the neuroendocrine changes associated with aging.

Role Played by Hypothalamic Nuclear Factor-κB in Alcohol-Mediated Activation of the Rat Hypothalamic-Pituitary-Adrenal Axis

The DNA binding protein nuclear factor-kappaB (NF-kappaB) is a transcription factor translocated from the cytosol to the nucleus in response to stressors. Here we determined whether the known ability of alcohol to activate the hypothalamic-pituitary axis was mediated by NF-kappaB, tested the hypothesis that this phenomenon was accompanied by increased hypothalamic NF-kappaB transcripts, and investigated some of the mechanisms involved in this response. We found that alcohol-induced increase in plasma ACTH was blunted by the intracerebroventricular (icv) injection of a cell-permeable peptide that inhibits NF-kappaB translocation. Alcohol also increased hypothalamic inhibitory factor kappaB (IkappaB) mRNA levels, a factor that regulates NF-kappaB protein activation and the activity of NF-kappaB DNA binding and whose expression is thought to reflect NF-kappaB activity. This response, which was not accompanied by detectable changes in brain levels of proinflammatory cytokines, was partially retained in adrenalectomized/corticosterone-replaced rats. The icv injection of corticotropin-releasing factor (CRF), a hypothalamic peptide that is released by alcohol and mediates its influence on ACTH secretion, also stimulated hypothalamic IkappaB transcription. We therefore determined whether brain CRF played a role in the influence of alcohol on NF-kappaB signaling pathways. Indeed, the icv injection of the CRF antagonist alpha-helCRF(9-41) decreased alcohol-induced hypothalamic IkappaB transcripts. Because this antagonist did not alter corticosterone levels, our data suggest that the role played by CRF was not modulated by this steroid. Collectively, our results provide evidence for a functional interaction between alcohol and NF-kappaB-dependent pathway in stimulating the rat hypothalamic-pituitary axis activity that involves independent roles of corticosterone and CRF.

Fluoxetine treatment of prepubescent rats produces a selective functional reduction in the 5-HT2A receptor-mediated stimulation of oxytocin

Various childhood mood disorders are being treated with serotonin selective reuptake inhibitors (SSRIs) such as fluoxetine (Prozac(R)), yet limited data are available on their effects on serotonergic systems prior to maturation. This study investigated the effects of chronic fluoxetine treatment on 5-HT2A serotonin receptor-mediated neuroendocrine responses in young male rats. Prepubescent male rats were treated with saline or fluoxetine (10 mg/kg/day, i.p.) for 14 days, a treatment regimen producing maximal changes in postsynaptic 5-HT2A function in adults. Eighteen hours post-treatment, the rats received saline or increasing doses (0.5, 2.0, or 5.0 mg/kg, i.p.) of the 5-HT2 receptor agonist (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl ((+/-)-DOI). Trunk blood was obtained to determine changes in oxytocin, ACTH, corticosterone, and renin responses. Fluoxetine produced a small ( approximately 6%) but significant reduction in body weight gain, but no changes were observed in basal hormone levels. In both saline- and fluoxetine-treated rats, (+/-)-DOI increased plasma oxytocin levels in a dose-dependent manner. However, the magnitude of the oxytocin responses to all doses of (+/-)-DOI were markedly attenuated ( approximately 50%) in the fluoxetine-treated rats, indicating a functional reduction in the E(max) of 5-HT(2A) receptor-mediated oxytocin responses. In contrast, fluoxetine did not alter the (+/-)-DOI-induced increases in plasma ACTH, corticosterone, or renin. These data provide the first demonstration of selective neuroadaptive responses in 55-HT2A serotonin receptor function due to prepubescent treatment with fluoxetine. These data may be clinically relevant with respect to the use of selective serotonin reuptake inhibitors in children and adolescents.

Possible Relationship between Elevated Plasma ACTH and Tall Stature in Familial Glucocorticoid Deficiency

Familial glucocorticoid deficiency (FGD) is characterized clinically by severe glucocorticoid deficiency associated with failure of adrenal responsiveness to ACTH but not with mineralcorticoid deficiency. Excessive growth was described previously in some patients with FGD, many of whom were shown to have mutations in the ACTH receptor gene. The mechanisms responsible for their excessive growth are unknown. We analyzed the ACTH receptor gene in three patients with FGD and discussed the causes of excessive growth in FGD. No mutations were detected in the coding and promoter regions of the ACTH receptor gene of one female patient who had tall stature (+ 2.41S.D.) and advanced bone age (10 years 9 months) when she was 4 years 9 months old. Her plasma ACTH level had been elevated until then (124-2,684 pg/ml). Moreover, plasma estradiol was elevated for her age (21.3 pg/ml), and it decreased in response to the dexamethasone suppression test (from 25.4 to 6.9 pg/ml). Elevated plasma estradiol was apparently related to the increase in plasma ACTH and played a major role in excessive growth in this patient. On the other hand, the genetic analysis showed that the other two patients who were siblings were homozygous for the R137W mutation. Clinically, they responded well to hydrocortisone replacement therapy with almost normal plasma ACTH levels. Although all patients with the R137W mutation reported previously were tall, our patients were of normal height. We speculate that the major causes of excessive growth in FGD are not only from ACTH receptor mutation, but also from the action of elevated plasma ACTH.

Glucocorticoid Receptor Blockade Disinhibits Pituitary-Adrenal Activity during the Stress Hyporesponsive Period of the Mouse

During postnatal development, mice undergo a period of reduced responsiveness of the pituitary-adrenal axis, the stress hyporesponsive period (SHRP), which is largely under control of maternal signals. The present study was designed to test the hypothesis that this quiescence in hypothalamic-pituitary-adrenal (HPA) activity is mediated by glucocorticoid feedback. For this purpose, the role of mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) in control of HPA activity was examined during the SHRP and in response to 24 h of maternal deprivation. Nondeprived or deprived (24 h) CD1 mice on postnatal d 8 were injected sc at 16 and 8 h before testing with the MR antagonist RU28318 or the GR antagonist RU38486. The results showed that, in nondeprived mice, blockade of GR rather than MR triggered a profound increase in anterior pituitary proopiomelanocortin mRNA, circulating ACTH, and corticosterone concentrations. In contrast, CRH mRNA in hypothalamus and GR mRNA in hippocampus and hypothalamus were decreased. Blockade of the GR during the deprivation period amplified the rise in corticosterone induced by maternal deprivation, whereas it reversed the deprivation effect on the other HPA markers, leading to profound increases in plasma ACTH, proopiomelanocortin mRNA expression in the anterior pituitary, CRH mRNA expression in the paraventricular nucleus, and MR mRNA expression in the hippocampus, but not in GR mRNA expression in the hippocampus and paraventricular nucleus. In conclusion, the data suggest that control of postnatal pituitary-adrenal activity during the SHRP involves GR-mediated feedback in the anterior pituitary, which is further potentiated in the absence of the mother.

Chronic morphine increases the pituitary–adrenocortical response of juvenile rats to mild stress

We previously reported that chronic exposure of adult male rats to morphine by pellet implantation has no effect on corticosterone secretion but causes a marked testosterone-dependent increase in CBG. In the studies reported here, we examined the effects of chronic morphine on the pituitary–adrenocortical axis of male rats prior to the developmental rise in testosterone. In contrast to adults, morphine had little effect on CBG in peripubertal males. We found nothing remarkable with regard to basal hormone levels; morphine caused only a transient increase in ACTH and corticosterone in juveniles. However, while the pituitary–adrenocortical response to mild stress was normal in adults exposed to morphine, it was markedly increased in juveniles. After 7 days of morphine exposure, the stress response was as much as 2.5 times greater than normal in morphine-treated juveniles. This exaggerated response to stress did not appear to be due to the passive withdrawal of morphine or to an additive effect of stress plus morphine. Instead, morphine may either increase the perceived severity of stressors or decrease sensitivity to the negative feedback effects of stress levels of corticosterone in juvenile males. Either way, there is a striking shift in morphine's effects on the pituitary–adrenocortical axis across development.

Encefalomielitis alérgica experimental en ratas sometidas a restricción calórica

This work analyzes the effect of calorie restriction on the development of experimental allergic encephalomyelitis (EAE) in Lewis rats. Plasma levels of ACTH, corticosterone, prolactin and growth hormone (GH) and mitogenic responses in submaxillary lymph nodes were measured. Male Lewis rats (6 weeks-old) were submitted to a calorie restriction equivalent to 66% of food restriction or to a normal diet. Fifteen days later, rats were injected with complete Freund's adjuvant plus spinal chord homogenate (SCH) or with complete Freund's adjuvant alone. Rats were monitored daily for clinical signs of EAE and were killed on day 15 after immunization. Only rats subjected to normal diet exhibited clinical signs of the disease. The increase in plasma ACTH and corticosterone found after SCH immunization in controls was not detectable in calorie restricted rats. Likewise, the correlation between circulating ACTH and corticosterone was no longer found after calorie restriction. Generally, calorie restriction by itself augmented plasma ACTH or corticosterone and this increase was not further amplified by SCH immunization. Only calorie restricted rats exhibited augmented plasma prolactin levels after SCH immunization, and decreased plasma GH levels regardless of immunization. Calorie restriction depressed the mitogenic response of lymphoid cells to concanavalin A but not to lipopolysaccharide. Calorie restricted rats did not exhibit augmented mitogenic response to concanavalin A following SCH immunization as those found in controls. The results are compatible with the view that the course of EAE can be significantly modified by caloric restriction.

Panic induction with cholecystokinin-tetrapeptide (CCK-4) Increases plasma concentrations of the neuroactive steroid 3alpha, 5alpha tetrahydrodeoxycorticosterone (3alpha, 5alpha-THDOC) in healthy volunteers.

3alpha-reduced neuroactive steroids such as 3alpha, 5alpha-tetrahydroprogesterone (3alpha, 5alpha-THP) and 3alpha, 5alpha-tetrahydrodeoxycorticosterone (3alpha, 5alpha-THDOC) are potent positive allosteric modulators of gamma-aminobutyric acid type A (GABAA) receptors and display pronounced anxiolytic activity in animal models. Experimental panic induction with cholecystokinin-tetrapeptide (CCK-4) and sodium lactate is accompanied by a decrease in 3alpha, 5alpha-THP concentrations in patients with panic disorder, but not in healthy controls. However, no data are available on 3alpha, 5alpha-THDOC concentrations during experimental panic induction. Therefore, we quantified 3alpha, 5alpha-THDOC concentrations in 10 healthy volunteers (nine men, one woman) before and after panic induction with CCK-4 by means of a highly sensitive and specific gas chromatography/mass spectrometry analysis. CCK-4 elicited a strong panic response as assessed by the Acute Panic Inventory. This was accompanied by an increase in 3alpha, 5alpha-THDOC, ACTH and cortisol concentrations. This increase in 3alpha, 5alpha-THDOC might be a consequence of hypothalamic-pituitary-adrenal (HPA) axis activation following CCK-4-induced panic, and might contribute to the termination of the anxiety/stress response following challenge with CCK-4 through enhancement of GABAA receptor function.