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L Givalois

Publications and source records attributed to L Givalois.

At least 19 recordsLinked to original sources
PubMed1998

The octadecaneuropeptide-induced response of corticotropin-releasing hormone messenger RNA levels is mediated by GABA(A) receptors and modulated by endogenous steroids.

The involvement of endogenous benzodiazepine octadecaneuropeptide in the regulation of corticotropin-releasing hormone messenger RNA expression has been studied using in situ hybridization technique. Intracerebroventricular injection of octadecaneuropeptide (4 microg/kg) induced a 26% decrease in the corticotropin-releasing hormone messenger RNA expression in the hypothalamic paraventricular nucleus. Concomitant injection of octadecaneuropeptide and i.p. injection of the GABA(A) receptor agonist muscimol (4 mg/kg) potentiated the corticotropin-releasing hormone messenger RNA decrease ( - 34%). The depressing effect of octadecaneuropeptide on corticotropin-releasing hormone gene expression was totally reversed by pretreatment of the animals with the GABA(A) receptor antagonist picrotoxin (5 mg/kg; i.p.) or by pretreatment with the benzodiazepine receptor antagonist flumazenil (4 mg/kg; i.p.). To determine the reciprocal involvement of adrenal and sexual steroids in this regulation, animals are adrenalectomized and/or castrated. Adrenalectomy reversed the effect induced by octadecaneuropeptide, which increased corticotropin-releasing hormone messenger RNA expression (+21%), while castration did not modify the negative influence of octadecaneuropeptide. When rats were adrenalectomized and castrated, the adrenalectomy influence was predominant, since octadecaneuropeptide increased significantly the hybridization signal (+18%). The involvement of neurosteroids, especially reduced metabolites of progesterone was also investigated. The concomitant injection of octadecaneuropeptide and subcutaneous injection of the 5alpha-reductase inhibitor MK-906 (14 mg/kg) to adrenalectomized and castrated rats, reduced significantly by 60% the increase of corticotropin-releasing hormone messenger RNA expression induced by octadecaneuropeptide. These results indicate that in vivo the endogenous benzodiazepine octadecaneuropeptide, via an activation of the benzodiazepine sites of the GABA(A) receptor, negatively modulates corticotropin-releasing hormone neuronal activity and that this modulation can be negatively or positively influenced by central and peripheral steroids.

Adrenalectomy↗
PubMed1998

Influence of adrenal glands on the modulation of prolactin gene expression by the endogenous benzodiazepine ligand octadecaneuropeptide in the male rat pituitary gland.

Recently, an 86-amino acid polypeptide with high affinity for diazepam binding sites, termed diazepam-binding inhibitor (DBI), has been found in the rat brain. DBI, as well as a peptide derived from DBI, the octadecaneuropeptide DBI[33-50] (ODN), interacts with the GABA(A) receptor complex. To investigate the role of these endogenous ligands for GABA(A) receptors on prolactin gene expression, we studied the effects of acute intracerebroventricular administration (4 h before sacrifice) of ODN on prolactin mRNA levels in the male rat. Because, in some neuropeptidergic systems, glucocorticoids play a role in the response to ODN, we also studied the influence of adrenal glands and the effect of dexamethasone administration in the response of prolactin gene expression to ODN. ODN injection produced an increase in prolactin mRNA levels. Adrenalectomy performed 5 days before sacrifice resulted in an increase in prolactin gene expression and also potentiated the stimulating effect of ODN. Because castration has been shown to decrease prolactin gene expression in the male rat, we used castrated and adrenalectomized animals to study the role of dexamethasone in the response of lactotrophs to ODN. In these steroid-deprived animals, dexamethasone treatment (for 4 days) decreased prolactin mRNA levels but did not modify the response to ODN. These data indicate that an endogenous neuropeptide interacting with the GABA(A) receptor complex can stimulate prolactin gene expression and suggest that the adrenal glands may produce factor(s) capable of decreasing prolactin mRNA. On the other hand, it does not appear that glucocorticoid hormones play a role in the effect of ODN on lactotroph activity.

Adrenal Glands↗
PubMed1998

Role of glucocorticoids in the modulation of corticotropin-releasing hormone mRNA level by the endogenous benzodiazepine receptor ligand octadecaneuropeptide in rat brain.

We have recently demonstrated that the endozepine octadecaneuropeptide (ODN) exerts an inhibitory influence on corticotropin-releasing hormone (CRH) mRNA expression. The effect is mediated by GABAA receptors and is reversed by adrenalectomy. In order to investigate the involvement of peripheral steroids and more particularly of glucocorticoids in the ODN modulation of CRH mRNA expression, we have evaluated, in adrenalectomized and castrated male rats (ADX/CX), the effect of dexamethasone (DEX) pretreatment on CRH mRNA expression induced by central injection of ODN. Variations in the CRH mRNA expression in the hypothalamic paraventricular nucleus have been studied using quantitative in situ hybridization. The intracerebroventricular injection of ODN (4 microg/kg), as previously reported, induced a significant inhibition of CRH mRNA expression in sham-operated rats (-33%). This inhibition was reversed in ADX/CX male rats (+65% vs. sham vehicle-injected rats and +20% vs. ADX/CX vehicle-injected rats). Pretreatment with DEX (5 mg/kg) during 4 days induced in ADX/CX rats a decrease of 22% (vs. ADX/CX vehicle-injected rats) in the CRH mRNA signal, which became comparable to that observed in sham vehicle-injected rats. Pretreatment of ADX/CX animals with DEX prevented the ODN-induced increase in CRH mRNA expression, inducing rather a 16 and 30% inhibition when compared to vehicle- and ODN-injected ADX/CX rats, respectively. Moreover the CRH mRNA levels observed in ODN-injected ADC/CX rats were higher than those observed in sham vehicle- and sham ODN-injected rats (+16% vs. sham vehicle-injected rats and +63% vs. sham ODN-injected rats). These results indicate that dexamethasone treatment in ADX/CX rats can restore mRNA levels to those observed in sham-operated animals but not the inhibiting effect induced by ODN. Together with previous findings, these results suggest that adrenal and/or gonadal factor(s) other than glucocorticoids are involved in ODN modulation of the HPA axis.

Adrenal Glands↗
PubMed1997

Dehydroepiandrosterone administration reverses the inhibitory influence of aging on gonadotrophin-releasing hormone gene expression in the male and female rat brain.

Dehydroepiandrosterone (DHEA) has been shown to exert a beneficial influence on some aging-associated deficits in rodents. It is well documented that in the rat, aging is associated with a decline in reproductive functions. In order to evaluate the effect of DHEA on GnRH gene expression in aged animals, we have studied the effect of 2.5-d administration of DHEA to young (50-54 d of age) and aged (18 mo of age) rats of both sexes. In the young males, DHEA induced an 18% reduction in the hybridization signal. In the aged animals, the mRNA levels were 10% lower than those observed in the young rats. DHEA completely restored the mRNA levels when compared to those detected in young male animals. In the young female, DHEA produced a 11% increase in GnRH mRNA, whereas, in the aged animals, hybridization signal was decreased by 28%. DHEA administration to aged females induced a 33% increase in the amount of mRNA, thus completely reversing the influence of aging. These results indicate that the decrease in GnRH gene expression which is likely involved in the loss of reproductive functions in aged rats can be totally reversed by a short term administration of DHEA which restored the GnRH neuronal activity. They also suggest that DHEA might play a role in the prevention and/or improvement of some deficits associated with aging through stimulation of GnRH biosynthesis.

Aging↗
PubMed1997

Role of adrenal and gonadal steroids in the response of GnRH gene expression to the endogenous benzodiazepine receptor ligand octadecaneuropeptide in the male rat brain.

We have recently demonstrated that the inhibitory influence of the endogenous benzodiazepine receptor ligand octadecaneuropeptide (ODN) on gonadotropin-releasing hormone (GnRH) gene expression could be prevented by specific inhibitors of 3 beta-hydroxysteroid dehydrogenase and 5 alpha-reductase in adrenalectomized and castrated male rats, then suggesting an involvement of neurosteroids in the action of ODN on GnRH neurons. In order to study in detail the role of circulating steroids in the effect of ODN, we have evaluated the influence of adrenalectomy, castration and the combination of adrenalectomy and castration as well as the effect of dexamethasone administration in the response of GnRH gene expression to ODN in the male rat. The intracerebroventricular injection of ODN (4 h before sacrifice) produced a 36% decrease in the hybridization signal. Adrenalectomy induced a 21% decrease in GnRH mRNA levels. In the adrenalectomized rats, the injection of ODN increased by 11% the amounts of mRNA. As previously reported by our group, castration was found to enhance GnRH mRNA (15% over control values). In castrated animals, ODN produced an inhibitory effect in the hybridization signal which was of the same amplitude as that observed in sham-operated animals. Finally, the combination of adrenalectomy and castration resulted in a small but significant decrease in the hybridization signal, the values being intermediary between those observed after adrenalectomy and those obtained after castration. In these animals, ODN induced a 38% decrease in the amounts of GnRH mRNA. In animals that had been castrated and adrenalectomized, dexamethasone treatment during 4 days produced a 19% increase in hybridization signal. In these dexamethasone-treated animals, ODN produced the usual decrease (33%) in GnRH mRNA. These results demonstrate that gonadal hormones do not play a major role in the activation of the GABAA receptor complex by ODN. On the other hand, it clearly appears that glucocorticoids exert a tonic stimulatory influence on GnRH neuronal activity and are involved in the inhibitory effect of ODN. The mechanism of action of glucocorticoids, which seems complex since the influence of adrenalectomy on the ODN action can be prevented by orchidectomy, remains to be fully elucidated.

3-Hydroxysteroid Dehydrogenases↗
PubMed1997

Age-related decrease in the hypothalamic CRH mRNA expression is reduced by dehydroepiandrosterone (DHEA) treatment in male and female rats.

Aging is frequently associated with changes in physiological and cognitive processes. Among these changes, it has been shown that aging has a profound impact on the hypothalamo-pituitary-adrenocortical (HPA) axis. Since there is controversy about the influence of aging on the HPA axis, the first objective of the present study was to clarify the effects of aging on the HPA axis using the genetic expression of hypothalamic corticotropin-releasing hormone (CRH). Changes in the CRH mRNA expression were quantified in the hypothalamic paraventricular nucleus (PVN) using in situ hybridization, in young (50 days) and old (18 months) rats of both sexes. The second objective was to determine the effects of dehydroepiandrosterone (DHEA) treatment on the age-related changes in CRH mRNA in both sexes. In aged animals of both sexes, CRH mRNA levels in PVN were significantly reduced by 20%. DHEA treatment increased the CRH mRNA expression in young rats and reversed the decrease in the CRH mRNA expression in old rats. Young males were more sensitive to DHEA than young females (+15% vs. +9%) whereas in old animals females showed more striking changes than males (+38% vs. +24%). These findings clearly demonstrate that in old apparently healthy rats of both sexes aging process induced a significant decrease in basal CRH mRNA levels and that DHEA treatment which exerts a positive influence on CRH gene expression completely reversed the decrease of the CRH mRNA levels associated with aging.

Aging↗
PubMed1997

Effects of aging and melatonin administration on gonadotropin-releasing hormones (GnRH) gene expression in the male and female rat.

It is well documented that in the rat of both sexes aging is associated with a decline in reproductive functions. We have recently shown that melatonin exerts a positive influence on GnRH gene expression in the adult male rats. In order to evaluate the effect of aging as well as melatonin on GnRH mRNA levels, we have studied the effect of 2.5-day administration of melatonin to young (50-55 day of age) and aged (18 month of age) rats of both sexes. In the young males melatonin induced a 11% increase in the hybridization signal. In the aged males, the GnRH mRNA levels were 13% lower than those observed in the young animals. Melatonin administration to aged animals completely restored GnRH mRNA levels when compared to those observed in the young untreated male rats. In contrast, melatonin did not modify the hybridization signal in young female rats, while aging induced a 20% decrease in mRNA levels. Melatonin administration to aged female induced a 18% increase in GnRH mRNA levels, thus completely reversing the influence of aging. These results indicate that the decrease in GnRH gene expression which is likely involved in the decline of reproductive functions in aging can be totally reversed by a short term administration of melatonin, then suggesting that the pineal hormone may be involved in the decrease of GnRH neuronal activity during aging.

Aging↗
PubMed1997

Involvement of neurosteroids in the effect of the endogenous benzodiazepine receptor ligand octadecaneuropeptide (ODN) on gonadotropin-releasing hormone gene expression in rat brain.

We have recently demonstrated that different activators of the GABAA receptor complex including reduced progesterone metabolites and the endozepine octodecaneuropeptide (ODN) exert an inhibitory influence on GnRH gene expression. In order to investigate the possible involvement of neurosteroids, especially progesterone metabolites in the effect of ODN, we have evaluated in adrenalectomized and castrated male rats the influence of pretreatment with an inhibitor of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) trilostane (TRIL) and an inhibitor of 5 alpha-reductase MK-906 on GnRH mRNA levels in ODN-treated rats. TRIL completely prevented the inhibitory influence of ODN on GnRH mRNA. It was also found that the inhibitor of 3 beta-HSD as well as pregnenolone sulfate (PREG-S), which has been shown to be increased following TRIL treatment, could induce an increase in GnRH mRNA. MK-906 could also completely reverse the negative influence of ODN. When administered alone, this antagonist of 5 alpha-reductase induced an increase in GnRH mRNA. These results clearly indicate that the inhibition of two key enzymes for the synthesis of reduced progesterone metabolites can completely prevent the inhibitory influence of the endozepine ODN, suggesting that the effect of this endogenous ligand might be completely or partially mediated by an activation of the synthesis of active progesterone metabolites. On the other hand, it remains possible that, as a consequence of enzymatic inhibition, an increase in some precursors known as antagonists of GABAA may play a role in the prevention of the ODN effect by the two enzyme antagonists.

3-Hydroxysteroid Dehydrogenases↗
PubMed1996

Different responses of plasma ACTH and corticosterone and of plasma interleukin-1 beta to single and recurrent endotoxin challenges.

In a parallel study in 10 individual rats, three time series of plasma concentrations of ACTH, corticosterone (CORT), and interleukin-1 beta (IL-1 beta) were measured before (time 0) and at intervals between 15 and 480 min following intra-arterial (i.a.) infusions of 25 microgram/kg lipopolysaccharide (LPS). All LPS injections were given at 9 AM. The first time series was performed on naive rats (day 1). A sequence of six daily injections (days 3-8) of the same dose of LPS followed. The post-LPS time course of the plasma ACTH, CORT and IL-1 beta levels were studies on days 3 (second injection) and 8 (seventh injection). The first LPS injection induced a rapid (30 min) eightfold rise in plasma ACTH and CORT, culminating in concentrations 30 times the baseline at 60 min (ACTH) and 15 times baseline at 120 min (CORT). Both hormones receded back to the initial basal level at 480 min. On the other hand, IL-1 beta increased slowly to peak at 13 times baseline 120 min before declining to minimal seven- to ninefold basal levels, 480 min and even 48 h post-LPS. During the second phase of the experiment starting 48 h after the initial LPS priming sequence, the ACTH and CORT responses to daily recurrent LPS injections again differed from those of IL-1 beta. The post-LPS time courses of the ACTH and CORT reaction displayed a typical pattern of a progressive attenuation studied at days 3 and 8. The peak amplitudes at days 3 and 8 were reduced to 60 and 10%, respectively, for ACTH, and to 85 and 45% for CORT of those observed at the first LPS test. The duration of the response (both) was also shortened from 480 min (first LPS test) to 300 min at days 3 and 8. The post-LPS patterns of the IL-1 beta responses were characterized, first by basal levels seven to nine times higher than the initial baseline values (day 1), and by a rapid suppression of the post-LPS response, with only a slight (30%) increase at day 3 and no increase at day 8. Thus, after both acute and recurrent LPS administration, ACTH/CORT and IL-1 beta reacted differently to the endotoxin challenge. The two LPS reactive systems were not correlated. This is inconsistent with the often proposed role of increased plasma IL-1 beta release as an intermediary factor in the LPS-induced recruitment of the corticotropic axis in general infections.

Adrenocorticotropic Hormone↗
PubMed1996

Involvement of central histamine in the early phase of ACTH and corticosterone responses to endotoxin in rats.

The involvement of histaminergic transmission in the rapid and sustained plasma ACTH and corticosterone (CORT) responses induced in conscious rats by intra-arterial infusions of 25 micrograms.kg-1 Escherichia coli lipopolysaccharide (LPS) was investigated. LPS challenge produced a rapid and transient increase (+ 62%) in the amount of histamine (HA) in the median eminence 15 min after LPS administration, which contrasted with constant concentrations of plasma HA throughout the entire study (up to 480 min). Blockade of histaminergic receptors by intra-arterial pretreatment with H1 or H2 antagonists (mepyramine, 1 mg/rat, and cimetidine, 2 mg/rat), administered separately, did not affect either ACTH or CORT responses to LPS. Pretreatment with the same doses of the two antagonists in combination very significantly but transiently impaired the earliest phase (30 min) of the ACTH and CORT responses, without any apparent effect on the late phase of these responses. Pretreatment of the animals with an H3-receptor agonist (R alpha-methylhistamine dihydrochloride, 1 mg/rat) similarly blunted the early corticotropic responses to LPS, and also slightly depressed the long-lasting CORT response. These findings support the view that activated central HA transmission may be a key intermediate mechanism triggering the CRH41-ACTH-CORT responses to LPS, in addition to the previously demonstrated activating role of catecholaminergic afferences to the CRH41 neurons during this early complex phase of corticotropic response to LPS.

Adrenocorticotropic Hormone↗
PubMed1995

Early hypothalamic activation of combined Fos and CRH41 immunoreactivity and of CRH41 release in push-pull cannulated rats after systemic endotoxin challenge.

We previously showed that intra-arterial endotoxin infusion (lipopolysaccharide [LPS]: 25 micrograms.kg-1) induced an early (15 min) and sustained (480 min) rise in plasma ACTH associated with delayed (60-120 min) increases in plasma concentrations of TNF alpha, IL-6, and IL-1 beta. In the present study, we followed the post-LPS time-course of immunocytochemical expression of Fos-like activity in CRH41 neurons whose immunolabeling was enhanced by icv colchicine pretreatment 48 h before the LPS, and CRH41 release in the push-pull cannulated median eminence of free-moving rats, in parallel with the ACTH response. The earliest Fos-like activity in IR-CHR41 neurons was detected 30 min post-LPS. Colchicine strongly inhibited the LPS-induced activation of Fos expression in single-labeled paraventricular neurons. CRH41 release in the median eminence displayed a biphasic stimulation pattern, with a first peak (+60%) at 15 min together with the ACTH surge, followed by a second rise beginning at 45 min and lasting more than 2 h. Thus, the early stage of the ACTH surge following a nonlethal endotoxin challenge (< 60 min) already involves the activation of CRH41-producing neurons.

Adrenocorticotropic Hormone↗
PubMed1995

[The corticotropic axis response after subcutaneous endotoxin injection is not associated with the increase of plasma interleukin-1 beta].

When injected through an intra-arterial (i. a.) cannula, LPS induced a rapid (15-30 min) and long-lasting (> 300 min) increase in plasma ACTH and corticosterone (CORT) levels. The duration of these responses depended on the LPS dose, and except for very small LPS doses, their amplitudes appeared independent of the dose of endotoxin. ACTH peaks (2,200 pg.ml-1) occurred between 30 and 120 min, whereas CORT always reached maximal levels at 120 min. Plasma Interleukin-1 beta (IL-1 beta) levels were always undetectable during the early phase of corticotropic stimulation, but increased strikingly 120 min after LPS injection. Increasing LPS doses, resulted in enhanced and prolonged IL-1 beta plasma circulating levels (up to 3.0 +/- 0.2 ng.ml-1). By contrast, no sub-cutaneous LPS dose used induced early increases in ACTH and CORT levels, whereas time-course of the hormonal response was evocative of the sustained phase of the corticotropic response to i. a. LPS, with both peaks occurring 120 min post-LPS. Increasing the s. c. LPS bolus 50-fold vs the i. a. dose did not affect the maximal amplitude of the ACTH response, whereas the amplitude of the CORT response, instead, appeared dependent on the LPS dose. On the other hand, even for the largest LPS doses, plasma IL-1 beta levels remained undetectable. Sub-cutaneous injection of LPS therefore appears as a new model for the study of the mechanisms of corticotropic responses to endotoxin without a direct involvement of bloodborne IL-1 beta.

Adrenocorticotropic Hormone↗
PubMed1995

Effects of pharmacological lesion of adrenergic innervation of the dorsal vagal nucleus on pancreatic insulin secretion in normal and vagotomized rats.

Previous morphological and physiological studies have suggested that the adrenergic innervation of the dorsal motor nucleus of the vagus nerve (dmnX) is involved in direct synaptic inhibition of parasympathetic preganglionic neurones of the vagus that control secretion of pancreatic insulin. We investigated the effects of bilateral 6-hydroxydopamine (6-OHDA) lesions of adrenergic innervation of the dmnX on pancreatic insulin secretion and glycaemia in normal and vagotomized rats. After two weeks the 6-OHDA lesions produced a marked increase in circulating insulin levels, but no change in glycaemia. Hyperinsulinaemia after adrenergic denervation of the dmnX was more pronounced when a glucose bolus was injected intraarterially. Bilateral subdiaphragmatic vagotomy reversed the observed hyperinsulinaemia. This targeted pharmacological lesion of the adrenergic innervation of dmnX thus causes hypersecretion by pancreatic B cells, an effect which requires an intact vagus nerve.

Animals↗
PubMed1994

Short-term but not long-term adrenalectomy modulates amplitude and frequency of the CRH41 episodic release in push-pull cannulated median eminence of free-moving rats.

CRH 41 release in push-pull cannulated median eminence (ME) was measured in unanesthetized male rats, 3 and 7 days after adrenalectomy (ADX) and in sham-lesioned controls. Perfusion started at 13.30 h and perfusate samples were collected at 5 min intervals for 3 h to estimate the mean release rate of CRH41. The major parameters of the neurohormone's episodic release pattern were analyzed using the Ultra algorithm. In a parallel study, 3 groups of similarly treated rats were used to measure plasma ACTH and hypothalamic CRH41. Three days after ADX, the plasma ACTH titers had risen 14-fold, the hypothalamic CRH41 content had decreased by 40%, while the CRH41 release in the ME had doubled as a result of a significant increase in most variables of the pulsatile release pattern: pulse frequency (+34%; P < 0.01), mean amplitude (+36%; P < 0.05), mean peak levels (+67%; P < 0.01) and mean pulse nadirs (x2.5; P < 0.01). Seven days after ADX, even though plasma ACTH had further increased to 30-times control levels, hypothalamic CRH41 content and CRH41 release in the ME had returned to almost control levels. The possible mechanisms of the discrepancy between the CRH and ACTH response time-courses following ADX are discussed.

Adrenal Glands↗
PubMed1994

Superior cervical ganglionectomy suppresses circadian corticotropic rhythms in male rats in the short term (5 days) and long term (10 days).

Superior cervical ganglionectomy (SCGx) has drastic effects on numerous hormonal circadian rhythms and particularly on pineal melatonin secretion. We investigated the hormonal consequences of ablation of the superior cervical ganglion on the corticotropic circadian rhythms in the male rat. Plasma were obtained by sampling blood every 4 h, using a chronic carotid cannula. Adreno-corticotropin hormone (ACTH) was assayed by radioimmunoassay (RIA) and corticosterone (B) by radiocompetition. Urinary 6-sulphatoxymelatonin (aMT6s), considered as an index of the pineal gland activity, was assayed by specific RIA: a decrease in the aMT6s concentration after ganglionectomy was taken as proof of adequate surgical operation. Control animals showed classical circadian rhythms for ACTH and B with basal values during the light phase and circadian peaks around the light/dark interface. Five and ten days after ganglionectomy, the circadian rhythms of ACTH and B were suppressed. In addition, the mean ACTH concentrations increased significantly 10 days after ganglionectomy compared to those in sham-operated rats and 5 days post-operation group. The mean plasma corticosterone levels were similar in those three groups of animals. This is the first study demonstrating the suppressive effect of superior cervical ganglionectomy on the circadian corticotropic hormonal cycle.

Adrenocorticotropic Hormone↗
PubMed1994

A subpopulation of corticotropin-releasing hormone neurosecretory cells in the paraventricular nucleus of the hypothalamus also contain NADPH-diaphorase.

The coexistence of ND with CRH 41 was explored in the parvicellular neurons of the PVN, using dual histochemical and radioimmunocytochemical labelling with the light microscope, in rats treated with colchicine. Even though the ND staining was scarce, a clear colocalization was evidenced in the parvicellular part of the PVN. Under these conditions, the ratio of neurons expressing both markers, ND and CRH, amounted about 15% of the CRH-containing neuron population. This result provides a useful tool to study morphological plastic changes in the PVN in response to environmental variations.

Animals↗
PubMed1994

Temporal cascade of plasma level surges in ACTH, corticosterone, and cytokines in endotoxin-challenged rats.

The present study was designed to investigate the coupling mechanisms linking the immune and the neuroendocrine corticotropic systems in an integrated defense response triggered by an infectious aggression. The experimental paradigm used consisted of the exploration in individual conscious rats of the temporal pattern of increased plasma concentrations of the two stress hormones, adrenocorticotropic hormone (ACTH) and corticosterone (Cort), and of three cytokines known as ACTH stimulators, tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1 beta, and IL-6, after intra-arterial infusions of lipopolysaccharide (LPS) given at three doses, 5 micrograms/kg (LPS-5), 25 micrograms/kg (LPS-25), and 1 mg/kg (LPS-1,000). Blood samples were taken 30 min and immediately before LPS injection (t0) and at 15, 30, 60, 120, 300, and 480 min post-LPS. The three doses of LPS induced ACTH and Cort surges, starting after 30 min for LPS-5 and LPS-25 or 15 min for LPS-1,000 and peaking with a similar amplitude at 60 min before receding slowly to baseline at 480 min for the two lower LPS doses. On the other hand, whatever the LPS dose, none of the three cytokines rose above undetectable basal levels before 60 min. They increased thereafter to culminate 10- to 30-fold above baseline at 60 min (TNF-alpha) or 120 min (IL-1 beta and IL-6) after LPS and declined back to basal levels at 300 min (TNF-alpha, all doses, and IL-6 for LPS-5 and LPS-25). After LPS-25, only IL-1 beta had not regressed to baseline levels at 480 min.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenocorticotropic Hormone↗