Activity Of CRH Neurons Research Articles

Molecular Mechanistic Insight Spirulina as Anti-Stress Agent

When under stress, our body reacts by releasing hormones and triggering the nervous system. The hypothalamic-pituitary-adrenal axis, which transmits the stress response, is in charge of the neuroendocrine adaptation of the stress response. Corticotrophin releasing hormone neurons control hypothalamic-pituitary-adrenal function. Increased. Many metabolic and neurological problems linked to stress are associated with the synthesis of corticotrophin releasing hormone. Gamma-aminobutyric acid (GABA) and GABAergic inhibition both play a significant role in controlling the activity of CRH neurons. Several synthetic medicines that target the GABAa receptor and activate GABAa activity are used to lessen the effects of stress. These treatments have relaxing effects but also come with a variety of negative effects. As they have no adverse effects and are harmless, anti-stress herbs are utilised as an alternative therapy to help the adrenal system. Spirulina platensis (commonly referred to as ‘Spirulina’), are well for their Immune system modulation; anti-viral activity; cancer preventive properties, and cardiovascular benefits. In present work an attempt had been made to evaluate the anti-stress potential of active constituent of spirulina by molecular docking.

Orexin facilitates the hypoxic ventilatory response via the activation of corticotropin-releasing hormone neurons that project to the nucleus of the solitary tract

The paraventricular nucleus of the hypothalamus (PVN) contributes significantly to the peripheral chemoreflex-mediated respiratory and sympathetic responses to hypoxia, in part via reciprocal interactions with nucleus of the solitary tract (nTS). Previously we showed that orexin neurons in the perifornical hypothalamus are activated by hypoxia and facilitate the hypoxic ventilatory response (HVR) in the active phase of the circadian cycle . The neural circuitry through which orexin facilitates the HVR is unknown. Orexin receptors (OxR) are expressed in the PVN, and we recently showed that OxR blockade reduced the activation of both corticotropin-releasing hormone neurons in the PVN as well as nTS neurons. In addition, hypoxia activated orexin neurons projecting to the PVN, but not those projecting to nTS. Here we further explored the hypothesis that orexin facilitates the HVR and arterial blood pressure (ABP) response to hypoxia via the activation of nTS-projecting CRH neurons, and that specific OxR1 knockdown in the PVN would reduce the HVR. To test these hypotheses, we nanoinjected fluorescent retrobeads bilaterally into the nTS to label nTS-projecting neurons. Rats were then exposed to hypoxia (2hrs at 11% O2 during the active phase) following injection of either suvorexant (OxR antagonist; 20 mg/kg i.p.; n=4), or vehicle (DMSO; n=4). Using immunohistochemistry (IHC) we then quantified the number of activated (i.e., Fos-immunoreactive; IR) nTS-projecting CRH neurons. In separate groups of rats we nanoinjected shRNA to knockdown Ox1R expression specifically in the PVN (n=8). PVN of control rats was nanoinjected with scrambled RNA (scRNA; n=3) or aCSF (n=2). Three weeks later, rats were exposed to graded hypoxia (from 21% to 10% inspired O2) over 3-5 minutes to assess the acute HVR and ABP response to different levels of hypoxia. OxR blockade reduced the number of Fos-IR, nTS-projecting CRH neurons by ~32% (drug: p<0.0001). Images confirmed successful targeting of shRNA to PVN, and OxR1 knockdown (by ~50%) was confirmed in subsets of samples by Western Blot and IHC. Ox1R knockdown specifically in the PVN had no effect on resting ventilation, but significantly reduced the HVR (main effect: p=0.02; 22% decrease in VE/VCO2 at 13% O2), due to a reduction in the respiratory frequency response to hypoxia (main effect: p=0.004; 38 breath/min decrease at 13% O2). Ox1R knockdown also decreased ABP (~5 mmHg at all O2 levels; main effect: p=0.0015), but not its response to hypoxia. These data suggest that orexin neurons facilitate the HVR via OxR1 Grants: 5R01HL098602 (EH, DK), 5R01HL136710 (KC) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Molecular Mechanistic Insight Spirulina as Anti-stress Agent

When under stress, our body reacts by releasing hormones and triggering the nervous system. The hypothalamic-pituitary-adrenal axis, which transmits the stress response, is in charge of the neuroendocrine adaptation of the stress response. Corticotrophin releasing hormone neurons control hypothalamic-pituitary-adrenal function Increased. Many metabolic and neurological problems linked to stress are associated with the synthesis of corticotrophin releasing hormone. Gamma-aminobutyric acid (GABA) and GABAergic inhibition both play a significant role in controlling the activity of CRH neurons. Several synthetic medicines that target the GABAa receptor and activate GABAa activity are used to lessen the effects of stress. These treatments have relaxing effects but also come with a variety of negative effects. As they have no adverse effects and are harmless, anti-stress herbs are utilised as an alternative therapy to help the adrenal system. Spirulina platensis (commonly referred to as ‘Spirulina’), are well for their Immune system modulation; anti-viral activity; cancer preventive properties, and cardiovascular benefits. In present work an attempt had been made to evaluate the anti-stress potential of active constituent of spirulina by molecular docking.

Should I Stay or Should I Go? CRHPVN Neurons Gate State Transitions in Stress-Related Behaviors.

Corticotropin-releasing hormone (CRH) neurons in the paraventricular nucleus of the hypothalamus are the canonical controllers of the endocrine response to stress. Here we propose a new role for these cells as a gate for state transitions that allow the organism to engage in stress-related behaviors. Specifically, we review evidence indicating that activation of these cells at critical times allows organisms to move to a state that is permissive for motor action. This is evident when the organism is under duress (defensive behavior), when the organism has successfully vanquished a threat (coping behavior), and when an organism initiates approach to a conspecific (social behavior). The motor behavior that follows from the activation of CRH neurons is not necessarily under the control of these cells but is determined by higher order circuits that discriminate more refined features of environmental context to execute the appropriate behavior.

The Central Amygdala Corticotropin-releasing hormone (CRH) Neurons Modulation of Anxiety-like Behavior and Hippocampus-dependent Memory in Mice

The encoding, consolidation and retrieval of memories is a multifaceted process that depends strongly on the optimal level of arousal but high levels of arousal may trigger anxiety, which negatively impacts the memory processing by the brain. We investigated the role of CRH neurons in the central amygdala (CeA) for their capacity to modulate both, the anxiety-like behavior and hippocampus-dependent memory. First, we activated the CRH neurons in CeA using cre-dependent AAV-DREADD in CRH-cre mice. The activation of CeA CRH neurons increased the anxiety-like behavior in Elevated-O maze (O-maze) and Light-Dark box (LDB). The activation of the CeA CRH also decreased Y-maze memory performance and the discrimination index in novel object recognition test (NOR). The inhibition of CeA CRH neurons with AAV-DREADD had the opposite effects on the anxiety-like behavior and the memory tests. Next, we used a combination of retrograde cre virus injected into locus ceruleus (LC) and cre-dependent AAV-DREADD injected into the CeA. While the excitation of the CeA neurons that project to LC increased the anxiety-like behavior, it also led to a better performance on the memory tests. The behavioral and memory effects were accompanied by increased c-Fos expression in the LC region. Pretreatment with CRH1 receptor antagonist antalarmin hydrochloride blocked the effects that were observed after the activation of the CeA projections to LC. Our findings highlight the role of CeA CRH neuronal population not only as a generator of anxiety but also demonstrate their role in the control of hippocampus-dependent memory.

Hypothalamic CRH neurons orchestrate complex behaviours after stress.

All organisms possess innate behavioural and physiological programmes that ensure survival. In order to have maximum adaptive benefit, these programmes must be sufficiently flexible to account for changes in the environment. Here we show that hypothalamic CRH neurons orchestrate an environmentally flexible repertoire of behaviours that emerge after acute stress in mice. Optical silencing of CRH neurons disrupts the organization of individual behaviours after acute stress. These behavioural patterns shift according to the environment after stress, but this environmental sensitivity is blunted by activation of PVN CRH neurons. These findings provide evidence that PVN CRH cells are part of a previously unexplored circuit that matches precise behavioural patterns to environmental context following stress. Overactivity in this network in the absence of stress may contribute to environmental ambivalence, resulting in context-inappropriate behavioural strategies.

Loss of GABAergic Inhibition in Hypothalamus in Chronic Stress

Chronic stress increases activity of hypothalamic‐pituitary‐adrenal (HPA) axis. CRH‐expressing neuron in the PVN is an essential component of HPA axis and plays a critical role in stress response. The activity of CRH neurons is regulated by excitatory and inhibitory GABAergic synaptic inputs. We hypothesized that chronic stress diminishes GABAergic inhibition, which contributes to hyperactivity of PVN‐CRH neurons. We identified PVN‐CRH neurons by expressing green fluorescent protein (GFP) driven by CRH promoter. Chronic unpredictable mild stress (CUMS) significantly increased plasma corticosterone levels. Blocking GABAA receptor significantly increased plasma corticosterone levels in unstressed rats. Furthermore, it significantly increased firing activity of PVN‐CRH neurons in unstressed rats but did not significant change in CUMS rats, while GABAA receptor significantly decreased firing activity of PVN‐CRH neurons in unstressed rats but slightly increased in CUMS rats. CUMS treatment significantly increased Na+‐K+‐2Cl‐ cotransporter (NKCC1) protein and mRNA levels while decreased K+‐2Cl‐ (KCC2) protein and mRNA levels in the PVN tissue. Immunocytochemical staining showed that they are expressed on CRH immunoreactivity positive PVN neurons. In addition, treatment with NKCC1 specific inhibitor decreased the basal firing activity of PVN‐CRH neurons in CUMS rats, but not in unstressed rats. Furthermore, it restored gabazine‐induced excitatory effect on PVN‐CRH neurons in CUMS rats. These data suggest that GABAergic inhibition in the PVN is diminished due to upregulation of NKCC1 in chronic stress.

Impact of repeated asenapine treatment on FosB/ΔFosB expression in neurons of the rat central nucleus of the amygdala: colocalization with corticoliberine (CRH) and effect of an unpredictable mild stress preconditioning.

FosB/ΔFosB expression in the central amygdalar nucleus (CeA) in response to repeated asenapine (ASE) treatment (an atypical antipsychotic used for the treatment of schizophrenia) was studied in normal rats and rats preconditioned with chronic unpredictable variable mild stress (CMS). The goal of this study was to reveal whether repeated ASE treatment for 14 days may: 1) induce FosB/ΔFosB expression in the amygdala, 2) activate CRH-synthesizing neurons in the CeA, and 3) interfere with 21 days lasting concomitant CMS preconditioning. Four groups of animals were studied: controls and ASE-, CMS-, and CMS+ASE-treated ones. CMS consisted of the restrain, social isolation, crowding, swimming, and cold and lasted 21 days. The ASE and CMS+ASE groups were from the 7th day of the experiment treated with ASE (0.3 mg/kg, subcutaneously - s.c.) twice a day, i.e. together for 14 days. Controls and CMS groups were treated with saline (300 µl/rat, s.c.) twice a day for 14 days. All the animals were sacrificed on the 22nd day, i.e. 16-18 hours after the last treatments. Single FosB/ΔFosB, FosB/ΔFosB colocalizations with CRH, and CRH immunolabeled perikarya were investigated in the CeA using a combined light and fluorescent immunohistochemistry. The distribution aspect of the black FosB/ΔFosB profiles was homogeneous over the whole CeA and no significant differences in the number of FosB/ΔFosB profiles between the individual groups of the rats really occurred. The level of colocalization pattern of FosB/ΔFosB in CRH perikarya was also very similar between the individual groups and in each case it reached approximately 10% of double-labeling. No differences were also seen in the number of CRH immunolabeled perikarya. The density of CRH nerve projections within the CeA was very alike in the individual groups of animals investigated. The study provides a new anatomical/functional finding about the lack of the stimulatory effect of the repeated ASE treatment on the expression of FosB/ΔFosB, FosB/ΔFosB/CRH colocalizations, and CRH immunolabeled perikarya number in the CeA. In addition, CMS preconditioning itself neither stimulated nor inhibited FosB/ΔFosB expression, nor altered the impact of ASE on the activity of CRH neurons in the CeA.

Contribution of Noradrenergic and Adrenergic Cell Groups of the Brainstem and Agouti-Related Protein-Synthesizing Neurons of the Arcuate Nucleus to Neuropeptide-Y Innervation of Corticotropin-Releasing Hormone Neurons in Hypothalamic Paraventricular Nucleus of the Rat

CRH-synthesizing neurons in the hypothalamic paraventricular nucleus (PVN) integrate neuronal and hormonal inputs and serve as a final common pathway to regulate the hypothalamic-pituitary-adrenal axis. One of the neuronal regulators of CRH neurons is neuropeptide Y (NPY) contained in axons that densely innervate CRH neurons. The three main sources of NPY innervation of the PVN are the hypothalamic arcuate nucleus and the noradrenergic and adrenergic neurons of the brainstem. To elucidate the origin of the NPY-immunoreactive (NPY-IR) innervation to hypophysiotropic CRH neurons, quadruple-labeling immunocytochemistry for CRH, NPY, dopamine-beta-hydroxylase, and phenylethanolamine-N-methyltransferase was performed. Approximately 63% of NPY-IR varicosities on the surface of CRH neurons were catecholaminergic (22% noradrenergic and 41% adrenergic), and 37% of NPY-IR boutons were noncatecholaminergic. By triple-labeling immunofluorescence detection of NPY, CRH, and agouti-related protein, a marker of NPY axons projecting from the arcuate nucleus, the noncatecholaminergic, NPY-ergic axon population was shown to arise primarily from the arcuate nucleus. When NPY was administered chronically into the cerebral ventricle of fed animals, a dramatic reduction of CRH mRNA was observed in the PVN (NPY vs. control integrated density units, 23.9 +/- 2.7 vs. 77.09 +/- 15.9). We conclude that approximately two thirds of NPY-IR innervation to hypophysiotropic CRH neurons originates from catecholaminergic neurons of the brainstem, whereas the remaining one third arises from the arcuate nucleus. The catecholaminergic NPY innervation seems to modulate the activation of CRH neurons in association with glucoprivation and infection, whereas the NPY input from the arcuate nucleus may contribute to inhibition of CRH neurons during fasting.

Differential Responses of Hypothalamus-Pituitary-Adrenal Axis Immediate Early Genes to Corticosterone and Circadian Drive

The hypothalamus-pituitary-adrenal (HPA) axis diurnal cycle of activity is manifest in circadian rhythms of ACTH and corticosterone secretion, which in the rat peak around the onset of the dark period. This cycle is thought to be driven by daily fluctuations in activity of CRH neurons within the paraventricular nucleus of the hypothalamus (PVN), controlled by suprachiasmatic nucleus inputs. In this study we examined whether the circadian drive that regulates ACTH and corticosterone basal secretion in the rat is reflected in PVN immediate early gene expression and, if so, whether different genes respond uniformly or uniquely to circadian stimulatory input. In addition, we examined how circadian drive and acute stress, two categories of stimuli that induce HPA axis activation, comparatively affect gene expression within different components of the HPA axis (c-fos mRNA, CRH heteronuclear RNA, and zif268 mRNA in PVN; c-fos mRNA, proopiomelanocortin heteronuclear RNA, and zinc finger 268 mRNA in anterior pituitary; c-fos mRNA and nerve growth factor I-B mRNA in adrenal cortex). Finally, we examined whether circadian differences in gene expression depend on endogenous glucocorticoids and, if so, whether the dependence is on an acute or permissive influence of the hormone. We found that a circadian drive that regulates HPA axis basal hormone secretion is also manifest on basal c-fos gene expression in the PVN. Moreover, we show that different immediate early genes within the HPA axis anatomical components display different diurnal patterns of gene expression. These differential patterns result, in part, from gene-specific responses to circadian signals and acute and/or permissive glucocorticoid actions.

NEUROENDOCRINE PERTURBATIONS IN FIBROMYALGIA AND CHRONIC FATIGUE SYNDROME

A large body of data from a number of different laboratories worldwide has demonstrated a general tendency for reduced adrenocortical responsiveness in CFS. It is still not clear if this is secondary to CNS abnormalities leading to decreased activity of CRH- or AVP-producing hypothalamic neurons. Primary hypofunction of the CRH neurons has been described on the basis of genetic and environmental influences. Other pathways could secondarily influence HPA axis activity, however. For example, serotonergic and noradrenergic input acts to stimulate HPA axis activity. Deficient serotonergic activity in CFS has been suggested by some of the studies as reviewed here. In addition, hypofunction of sympathetic nervous system function has been described and could contribute to abnormalities of central components of the HPA axis. One could interpret the clinical trial of glucocorticoid replacement in patients with CFS as confirmation of adrenal insufficiency if one were convinced of a positive therapeutic effect. If patient symptoms were related to impaired activation of central components of the axis, replacing glucocorticoids would merely exacerbate symptoms caused by enhanced negative feedback. Further study of specific components of the HPA axis should ultimately clarify the reproducible abnormalities associated with a clinical picture of CFS. In contrast to CFS, the results of the different hormonal axes in FMS support the assumption that the distortion of the hormonal pattern observed can be attributed to hyperactivity of CRH neurons. This hyperactivity may be driven and sustained by stress exerted by chronic pain originating in the musculoskeletal system or by an alteration of the CNS mechanism of nociception. The elevated activity of CRH neurons also seems to cause alteration of the set point of other hormonal axes. In addition to its control of the adrenal hormones, CRH stimulates somatostatin secretion at the hypothalamic level, which, in turn, causes inhibition of growth hormone and thyroid-stimulating hormone at the pituitary level. The suppression of gonadal function may also be attributed to elevated CRH because of its ability to inhibit hypothalamic luteinizing hormone-releasing hormone release; however, a remote effect on the ovary by the inhibition of follicle-stimulating hormone-stimulated estrogen production must also be considered. Serotonin (5-HT) precursors such as tryptophan (5-HTP), drugs that release 5-HT, or drugs that act directly on 5-HT receptors stimulate the HPA axis, indicating a stimulatory effect of serotonergic input on HPA axis function. Hyperfunction of the HPA axis could also reflect an elevated serotonergic tonus in the CNS of FMS patients. The authors conclude that the observed pattern of hormonal deviations in patients with FMS is a CNS adjustment to chronic pain and stress, constitutes a specific entity of FMS, and is primarily evoked by activated CRH neurons.

Corticotropin-releasing hormone synthesizing neurons in the hypothalamic paraventricular nucleus of rats neonatally treated with monosodium glutamate can respond to different stress paradigms

Neonatal administration of monosodium glutamate (MSG) produces pathological lesions in many brain regions. There are indications that MSG treatment could also influence the neurons of the hypothalamic paraventricular nucleus (PVN). The goal of this study was to find out whether MSG treatment could alter the activity of the corticotropin-releasing hormone synthesizing neurons, i.e. the principal regulators of the corticotropin hormone secretion, located in the medial posterior subdivision of the PVN. The activity of CRH neurons was assessed by changes in CRH mRNA levels in response to both stimulatory and inhibitory conditions induced by immobilization and water deprivation, respectively. In addition, effect of the circulating glucocorticoid deficit induced by bilateral adrenalectomy was investigated. The obtained data show that in MSG-treated animals the rise in CRH mRNA in response to immobilization stress and adrenalectomy as well as the decrease after water deprivation were similar to the changes seen in controls. In addition POMC mRNA changes in MSG-treated animals indicate an uninterrupted capability of CRH neurons to transform different signals to corticotropin cells. It can be concluded that CRH neurons of the PVN are not functionally altered, in spite of the widespread neurotoxic effect of MSG treatment. [Neurol Res 1999; 21: 775–780]

On the Gender Differences in Sleep-Endocrine Regulation in Young Normal Humans

Sleep-endocrine regulation in humans involves high activity of the somatotropic axis at the beginning of the night and an increase in the hypothalamic-pituitary-adrenocortical (HPA) system during the night. Gender differences were examined with regard to sleep-endocrine regulation in young healthy controls (10 men, 9 women). The sleep EEG was recorded (23:00–07:00 h) and plasma samples were collected and analyzed for GH, cortisol and ACTH at 20-min intervals. Cortisol secretion was significantly higher in females during the first half of the night (F = 9.9, p < 0.05), while ACTH was not different. In women, sleep-EEG analysis showed less slow wave sleep (SWS) during the second half of the night (F = 4.5, p < 0.05) and a significantly greater decrease in SWS and delta activity from the first to the second half of the night (F = 3.7 and 7.4, respectively, p < 0.05). Sigma activity increased during the night in women only (F = 3.7, p < 0.05). Our data are compatible with the hypothesis that in women compared to men activity of hypothalamic CRH neurons and central CRH release is greater, but is not reflected by greater HPA activity.

Cellular and extracellular regulatory mechanisms of hypothalamic corticotropin-releasing hormone neurons.

CRH is produced in the parvocellular division of the PVN and released into the hypophysial portal circulation to stimulate ACTH synthesis and secretion, thus playing a critical role in the HPA axis regulation. The activity of CRH neurons is regulated by humoral factors such as glucocorticoid and IL-1 as well as numerous kinds of neural inputs within and from outside of the hypothalamus. Circulating glucocorticoids readily have access to the CRH neurons and thereby exert a potent inhibitory action on CRH gene transcription. The molecular mechanisms involved in the glucocorticoid negative feedback remain to be fully understood. IL-1, produced in the periphery during the inflammatory process, is a potent stimulatory factor for CRH neurons. It is not yet clear how a protein of this large molecular weight has access to brain tissues through the blood brain barrier, nor is it clear through which neural pathway the IL-1-mediated signal is conveyed to the hypothalamus.A number of neurotransmitter/modulator candidates have been implicated in the regulation of CRH neurons. Functional roles and anatomical pathways have been explored by pharmacological methods, ablation of specific neural pathway(s), and the neural tracingethod. Despite the substantial knowledge produced by these studies, physiological and/or pathophysiological roles of the respective neural circuitry are still obscure.Two major intracellular signal transduction systems, the CAMP-dependent PKA pathway and diacylglycerol-dependent PKC pathway, are implicated in transcriptional regulation of the CRH gene. The functionality of the CRE, 5'-flanking the CRH gene, has been well established in cell culture system transfected with CRH promoter-reporter constructs, thus the cAMP-dependent PKA pathway may play an essential role in CRH gene expression. The role of the PKC pathway is still controversial and requires further exploration.

Transient suppression of resting corticosterone levels induces sustained increase of AVP stores in hypothalamic CRH-neurons of rats.

Previous studies showed that various stressors can induce delayed (days) and long-lasting (weeks) increases of vasopressin (AVP) stores in terminals of CRH neurons in the external zone of the median eminence (ZEME) in adult rats. Here we tested whether this long-lasting neuroplastic change can be induced by mechanisms other than stressor provoked transsynaptic activation of CRH neurons. Single i.v. administration of a CRH antibody to adult rats causes a delayed (at least 1 day) and long-lasting (3 weeks) increase (2-3 fold) of AVP stores in the ZEME without affecting CRH stores. It suppresses ether-induced ACTH-responses for at least 8 days. In contrast, resting pm levels of ACTH and corticosterone (CORT) were suppressed only during the first 2 days. Suppletion of CORT levels on day 1 and 2, attenuates the antibody induced AVP-increase by 57%. CRH-immunoneutralization did not affect the AVP stores in CORT supplemented ADX rats. Thus, long-term increases of AVP stores induced by CRH-immunoneutralization largely depend on short-term suppression of pm CORT levels. Accordingly, single administration of metyrapone, which causes a transient suppression of pm CORT levels, increases AVP (1.5 fold) but not CRH stores one week later. We conclude that transient activation of hypothalamic CRH neurons results in long-lasting increases in AVP co-expression irrespective of the nature of the activating stimulus.

Histamine stimulates c-fos expression in hypothalamic vasopressin-, oxytocin-, and corticotropin-releasing hormone-containing neurons

The stimulatory action of centrally administered histamine (HA) on secretion of the anterior pituitary hormones ACTH, beta-endorphin, and PRL is indirect, and previous studies have suggested that hypothalamic neurons containing CRH, arginine vasopressin (AVP), and oxytocin (OT) are involved in this response. We studied the effect of HA on neuronal activation in the hypothalamus by investigating the expression of c-fos, which is a protooncogene activated early when neurons are stimulated. The expression of c-fos was evaluated by detection of c-fos immunoreactivity (c-fos-IR) using immunohistochemistry and by measurement of c-fos mRNA using in situ hybridization techniques. In addition, the identity of the HA-stimulated neurons was investigated by dual antigen immunohistochemistry visualizing AVP-, OT-, or CRH-IR in the neurons showing increased c-fos expression. HA (270 nmol) infused intracerebroventricularly increased c-fos-IR in the hypothalamus, especially in the periventricular hypothalamic areas and certain hypothalamic nuclei, including the paraventricular nucleus (PVN) and supraoptic nucleus (SON). c-fos-immunoreactive nuclei were observed throughout the SON, whereas in the PVN, c-fos-IR was particularly pronounced in the subnuclei known to contain AVP, OT, and CRH neurons. Double labeling experiments confirmed that c-fos was expressed in AVP-, OT-, and CRH-immunoreactive as well as other neurons. In addition, HA intracerebroventricularly induced a moderate expression of c-fos-IR in the arcuate nucleus. In situ hybridization showed increased levels of c-fos mRNA in both the PVN and SON after HA infusion. We conclude that HA-induced secretion of ACTH, beta-endorphin, and PRL may be mediated via activation of hypothalamic AVP, OT, and CRH neurons.

Histamine stimulates c-fos expression in hypothalamic vasopressin-, oxytocin-, and corticotropin-releasing hormone-containing neurons.

The stimulatory action of centrally administered histamine (HA) on secretion of the anterior pituitary hormones ACTH, beta-endorphin, and PRL is indirect, and previous studies have suggested that hypothalamic neurons containing CRH, arginine vasopressin (AVP), and oxytocin (OT) are involved in this response. We studied the effect of HA on neuronal activation in the hypothalamus by investigating the expression of c-fos, which is a protooncogene activated early when neurons are stimulated. The expression of c-fos was evaluated by detection of c-fos immunoreactivity (c-fos-IR) using immunohistochemistry and by measurement of c-fos mRNA using in situ hybridization techniques. In addition, the identity of the HA-stimulated neurons was investigated by dual antigen immunohistochemistry visualizing AVP-, OT-, or CRH-IR in the neurons showing increased c-fos expression. HA (270 nmol) infused intracerebroventricularly increased c-fos-IR in the hypothalamus, especially in the periventricular hypothalamic areas and certain hypothalamic nuclei, including the paraventricular nucleus (PVN) and supraoptic nucleus (SON). c-fos-immunoreactive nuclei were observed throughout the SON, whereas in the PVN, c-fos-IR was particularly pronounced in the subnuclei known to contain AVP, OT, and CRH neurons. Double labeling experiments confirmed that c-fos was expressed in AVP-, OT-, and CRH-immunoreactive as well as other neurons. In addition, HA intracerebroventricularly induced a moderate expression of c-fos-IR in the arcuate nucleus. In situ hybridization showed increased levels of c-fos mRNA in both the PVN and SON after HA infusion. We conclude that HA-induced secretion of ACTH, beta-endorphin, and PRL may be mediated via activation of hypothalamic AVP, OT, and CRH neurons.

Thyroid and Adrenal Dysfunction in Abstinent Alcoholic Men: Locus of Disturbance

Certain neuroendocrine abnormalities (e.g., blunted plasma adrenocorticotropic hormone [ACTH] response to corticotropin-releasing hormone [CRH] administration and blunted serum TSH response to thyrotropin-releasing hormone [TRH] administration) are common in alcoholic patients. It was the objective of this study to evaluate whether they are centrally mediated: that is, whether they are secondary to increased activity of CRH and/or TRH neurons. We evaluated the nocturnal secretion (2200 hours to 1000 hours, q 15 min) of plasma ACTH, serum cortisol, and serum TSH, and their responses to the combined administration of CRH and TRH, in 28 acutely abstinent alcoholic (age range: 32 to 57 years; mean: 42.4 years) and 19 normal men (age range: 21 to 52 years; mean: 32.1 years). To assess the validity of administering CRH and TRH simultaneously, we gave 10 additional abstinent alcoholic men (age range: 36 to 53 years; mean: 45.8 years), in random order and at least 4 days apart, either CRH, TRH, placebo, or CRH plus TRH. Nocturnal ACTH, cortisol, and TSH secretion, as well as cortisol and TSH responses after CRH plus TRH administration, were similar in alcoholic and normal men. However, ACTH peak responses to CRH plus TRH were reduced in the alcoholic men (p < 0.05). The ACTH, but not cortisol, response was greater after combined CRH plus TRH administration than after CRH alone (p < .002). The blunted ACTH response does not appear to be the result of increased endogenous CRH activity, because all parameters of nocturnal ACTH pulsatility were normal in the alcoholics. It rather appears to be secondary to an intrinsic defect in the CRH responsiveness of the pituitary corticotroph, possibly due to genetic vulnerability or to the toxic effects of prolonged alcohol abuse.