Functional characterization of the hypothalamic-pituitary-adrenal axis of the Wistar Audiogenic Rat (WAR) strain

The Wistar Audiogenic Rat (WAR) strain is a genetic model of sound-induced reflex epilepsy which was selected starting from audiogenic seizures susceptible Wistar rats. Wistar resistant rats were used as WAR`s control in this study. In the acute situation, audiogenic seizures (AS) in WARs mimic tonic-clonic seizures and, in the chronic protocol, mimic temporal lobe epilepsy. AS have been shown to evoke neuroendocrine responses; however, the hypothalamic-pituitary-adrenal activity in the WAR has not been established. The aim of this study was to evaluate the hypothalamic-pituitary-adrenal axis (HPA) responses to exogenous ACTH stimulation (8 ng/rat), fifteen minute restraint stress and circadian variation (8 am and 8 pm) under rest conditions in these animals through plasma measurements of ACTH and corticosterone concentrations. We also measured the body weight from birth to the 9th week of life and determined adrenal gland weight. We found that WARs are smaller than Wistar and presented a higher adrenal gland weight with a higher level of corticosterone release after intravenous ACTH injection. They also showed altered HPA axis circadian rhythms and responses to restraint stress. Our data indicate that, despite the lower body weight, WARs have increased adrenal gland weight associated with enhanced pituitary and adrenal responsiveness after HPA axis stimulation. Thus, we propose WARs as a model to study stress-epilepsy interactions and epilepsy-neuropsychiatry comorbidities. (C) 2011 Elsevier B.V. All rights reserved.

Escitalopram prolonged fear induced by simulated public speaking and released hypothalamic-pituitary-adrenal axis activation

Simulated public speaking (SPS) test is sensitive to drugs that interfere with serotonin-mediated neurotransmission and is supposed to recruit neural systems involved in panic disorder. The study was aimed at evaluating the effects of escitalopram, the most selective serotonin-selective reuptake inhibitor available, in SPS. Healthy males received, in a double-blind, randomized design, placebo (n = 12), 10 (n = 17) or 20 (n = 14) mg of escitalopram 2 hours before the test. Behavioural, autonomic and neuroendocrine measures were assessed. Both doses of escitalopram did not produce any effect before or during the speech but prolonged the fear induced by SPS. The test itself did not significantly change cortisol and prolactin levels but under the higher dose of escitalopram, cortisol and prolactin increased immediately after SPS. This fear-enhancing effect of escitalopram agrees with previously reported results with less selective serotonin reuptake inhibitors and the receptor antagonist ritanserin, indicating that serotonin inhibits the fear of speaking in public.

Is Suppression of Hypothalamic-Pituitary-Adrenal Axis Significant During Clinical Treatment of Phimosis?

Purpose: Corticoids have been an option for phimosis treatment since 1993. However, long-term use or repeated cycles pose a concern regarding drug absorption and consequent systemic effects. The aim of this study was to investigate the effect of topical corticoids used in treating phimosis on the hypothalamus-pituitary-adrenal axis in children. Materials and Methods: A total of 31 children were included in the study. Cortisol secretion was evaluated by the measurement of salivary cortisol in saliva samples collected at 9:00 a.m, before starting treatment and after 8 weeks of topical treatment with 0.05% clobetasol propionate. Salivary cortisol was determined by radioimmunoassay. To confirm that use of clobetasol propionate was not detected by the assay, the presence of cortisol circadian rhythm was checked by an extra saliva sample obtained at 11:00 p.m. from 10 children, and was observed to be maintained in all of them. Results: No significant difference in salivary cortisol levels was observed between samples obtained at 9:00 a.m. before starting treatment and after completing treatment when the entire group was analyzed. However, in 2 children the salivary cortisol levels after treatment were lower than the cutoff value (358 ng/dl) assumed to be suggestive of hypothalamus-pituitary-adrenal axis suppression. Conclusions: Topical clobetasol propionate used twice daily for clinical treatment of phimosis does not affect the hypothalamus-pituitary-adrenal axis in most patients. However, salivary cortisol level should be considered as a laboratory marker in long-term treatment or during repeated cycles to detect possible hypothalamus-pituitary-adrenal axis suppression.

New molecular variants of hypothalamus-pituitary-gonad axis genes and their association with early puberty phenotype in Bos taurus indicus (Nellore)

Endocrine system plays a major role in the control of reproductive functions which are regulated by the hypothalamus-pituitary-gonad axis and its interactions. FSH and LH receptor genes are expressed at the gonads and GnRH receptor gene is expressed at the anterior pituitary gland. Misense mutations of the FSH, LH or GnRH receptors, activating or inactivating their functions in mammals, are potentially useful to allow the understanding of the role of this group of gonadotropins in reproductive phenotypes as early puberty and birth interval length. In the present study, polymorphisms in bovine exon 11 and 3`UTR of LHR, exon 10 and 3`UTR of FSHR and GnRHR genes were characterized with some of them resulting in changes in the aminoacidic chain. These polymorphic sites were found in a Bos taurus indicus (Nellore) female population by means of PCR-SSCP and DNA sequencing. Association between nucleotidic/aminoacidic changes and early puberty were determined by Chi-square analysis. It was found association between FSHR 3`UTR polymorphisms at position 2181, 2248 and 2249 bp and early puberty phenotype (p < 0.05). The presence of these new molecular markers might be considered in further studies to validate its correlation with early puberty or other reproduction associated phenotypes in cattle breeds. (C) 2007 Published by Elsevier B.V.

Acute reversible inactivation of the bed nucleus of stria terminalis induces antidepressant-like effect in the rat forced swimming test

Background: The bed nucleus of stria terminalis (BNST) is a limbic forebrain structure involved in hypothalamo-pituitary-adrenal axis regulation and stress adaptation. Inappropriate adaptation to stress is thought to compromise the organism's coping mechanisms, which have been implicated in the neurobiology of depression. However, the studies aimed at investigating BNST involvement in depression pathophysiology have yielded contradictory results. Therefore, the objective of the present study was to investigate the effects of temporary acute inactivation of synaptic transmission in the BNST by local microinjection of cobalt chloride (CoCl(2)) in rats subjected to the forced swimming test (FST). Methods: Rats implanted with cannulae aimed at the BNST were submitted to 15 min of forced swimming (pretest). Twenty- four hours later immobility time was registered in a new 5 min forced swimming session (test). Independent groups of rats received bilateral microinjections of CoCl(2) (1 mM/100 nL) before or immediately after pretest or before the test session. Additional groups received the same treatment and were submitted to the open field test to control for unspecific effects on locomotor behavior. Results: CoCl(2) injection into the BNST before either the pretest or test sessions reduced immobility in the FST, suggesting an antidepressant-like effect. No significant effect of CoCl(2) was observed when it was injected into the BNST immediately after pretest. In addition, no effect of BNST inactivation was observed in the open field test. Conclusion: These results suggest that acute reversible inactivation of synaptic transmission in the BNST facilitates adaptation to stress and induces antidepressant-like effects.

Role of the bed nucleus of the stria terminalis in the cardiovascular responses to acute restraint stress in rats

The aim of this work was to test the hypothesis that the bed nucleus of the stria terminalis (BST) and noradrenergic neurotransmission therein mediate cardiovascular responses to acute restraint stress in rats. Bilateral microinjection of the non-specific synaptic blocker CoCl2 (0.1nmol/100nl) into the BST enhanced the heart rate (HR) increase associated with acute restraint without affecting the blood pressure increase, indicating that synapses within the BST influence restraint-evoked HR changes. BST pretreatment with the selective 1-adrenoceptor antagonist WB4101 (15nmol/100nl) caused similar effects to cobalt, indicating that local noradrenergic neurotransmission mediates the BST inhibitory influence on restraint-related HR responses. BST treatment with equimolar doses of the 2-adrenoceptor antagonist RX821002 or the -adrenoceptor antagonist propranolol did not affect restraint-related cardiovascular responses, reinforcing the inference that 1-adrenoceptors mediate the BST-related inhibitory influence on HR responses. Microinjection of WB4101 into the BST of rats pretreated intravenously with the anticholinergic drug homatropine methyl bromide (0.2mg/kg) did not affect restraint-related cardiovascular responses, indicating that the inhibitory influence of the BST on the restraint-evoked HR increase could be related to an increase in parasympathetic activity. Thus, our results suggest an inhibitory influence of the BST on the HR increase evoked by restraint stress, and that this is mediated by local 1-adrenoceptors. The results also indicate that such an inhibitory influence is a result of parasympathetic activation.

GABAergic mediation of stress-induced secretion of corticosterone and oxytocin, but not prolactin, by the hypothalamic paraventricular nucleus

The hypothalamus-pituitary-adrenal axis (HPA) participates in mediating the response to stressful stimuli. Within the HPA, neurons in the medial parvocellular region of paraventricular nucleus (PVN) of the hypothalamus integrate excitatory and inhibitory signals triggering secretion of corticotropin-releasing hormone (CRH), the main secretagogue of adrenocorticotropic hormone (ACTH). Stressful situations alter CRH secretion as well as other hormones, including prolactin and oxytocin. Most inputs to the PVN are of local origin, half of which are GABAergic neurons, and both GABA-A and GABA-B receptors are present in the PVN. The objective of the present study was to investigate the role of GABA-A and GABA-B receptors in the PVN`s control of stress-induced corticosterone, oxytocin and prolactin secretion. Rats Were microinjected with saline or different doses (0.5, 5 and 50 pmol) of GABA-A (bicuculine) or GABA-B (phaclofen) antagonists in the PVN. Ten minutes later, they were subjected to a stressor (ether inhalation) and blood samples were collected 30 min before and 10, 30, 60, 90 and 120 min after the stressful stimulus to measure hormone levels by radioimmunoassay. Our results indicate that GABA acts in the PVN to inhibit stress-induced corticosterone secretion via both its receptor subtypes, especially GABA-B. In contrast, GABA in the PVN stimulates oxytocin secretion through GABA-B receptors and does not alter prolactin secretion. (C) 2008 Elsevier Inc. All rights reserved.

Hypothalamic supraoptic but not paraventricular nucleus is involved in cardiovascular responses to carbachol microinjected into the bed nucleus of stria terminalis of unanesthetized rats

Microinjection of the cholinergic agonist carbachol into the bed nucleus of the stria terminalis (BST) has been reported to cause pressor response in unanesthetized rats, which was shown to be mediated by an acute release of vasopressin into the systemic circulation and followed by baroreflex-mediated bradycardia. In the present study, we tested the possible involvement of the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei in the pressor response evoked by carbachol microinjection into the BST of unanesthetized rats. For this, cardiovascular responses following carbachol (1 nmol/100 nL) microinjection into the BST were studied before and after PVN or SON pretreatment, either ipsilateral or contralateral in relation to BST microinjection site, with the nonselective neurotransmission blocker cobalt chloride (CoCl(2), 1 mM/100 nL). Carbachol microinjection into the BST evoked pressor response. Moreover, BST treatment with carbachol significantly increased plasma vasopressin levels, thus confirming previous evidences that carbachol microinjection into the BST evokes pressor response due to vasopressin release into the circulation. SON pretreatment with CoCl(2), either ipsilateral or contralateral in relation to BST microinjection site, inhibited the pressor response to carbachol microinjection into the BST. However, CoCl(2) microinjection into the ipsilateral or contralateral PVN did not affect carbachol-evoked pressor response. In conclusion, our results suggest that pressor response to carbachol microinjection into the BST is mediated by SON magnocellular neurons, without significant involvement of those in the PVN. The results also indicate that responses to carbachol microinjection into the BST are mediated by a neural pathway that depends on the activation of both ipsilateral and contralateral SON. (C) 2011 Elsevier B.V. All rights reserved.

Involvement of hypothalamic paraventricular nucleus non-N-methyl-d-aspartate receptors in the pressor response to noradrenaline microinjected into the bed nucleus of the stria terminalis of unanesthetized rats

Microinjection of noradrenaline into the bed nucleus of the stria terminalis (BST) has been reported to cause a pressor response in unanesthetized rats, which was shown to be mediated by acute vasopressin release into the systemic circulation. In the present study we verified the involvement of magnocellular neurons of the hypothalamic paraventricular (PVN) or supraoptic (SON) nuclei and the local neurotransmitter involved in the pressor response to noradrenaline microinjection into the BST. The PVN pretreatment with the non-selective neurotransmission blocker CoCl(2) (1 nmol/100 nL) inhibited the noradrenaline-evoked pressor response. However, responses were not affected by SON treatment with CoCl(2). Further experiments were carried out to test if glutamatergic neurotransmission in the PVN mediates the pressor response evoked by noradrenaline microinjection into the BST. Pretreatment of the PVN with the selective N-methyl-d-aspartate (NMDA) receptor antagonist LY235959 (2 nmol/100 nL) did not affect the noradrenaline-evoked pressor response. However, PVN pretreatment with the selective non-NMDA receptor antagonist NBQX (2 nmol/100 nL) significantly reduced the pressor response to noradrenaline microinjection into the BST. In conclusion, our results suggest that pressor responses to noradrenaline microinjection into the BST are mediated by PVN magnocellular neurons without involvement of SON neurons. They also suggest that a glutamatergic neurotransmission through non-NMDA glutamate receptors in the PVN mediates the response.

Modulatory role of locus coeruleus and estradiol on the stress response of female rats

The activity of the hypothalamic-pituitary-adrenal axis is modulated by the norepinephrinergic system and, in females, also by the ovarian hormones. We investigated the role of ovarian steroids and the locus coeruleus (LC) on stress-induced corticosterone secretion in female rats. Ovariectomized rats without hormonal replacement (OVX) or treated with estradiol (OVE) or estradiol plus progesterone (OVEP) were subjected to jugular cannulation. Immediately after that, each hormonal treatment group was subjected to LC lesion or sham surgery or no brain surgery. After 24 h, blood samples of all 9 groups were collected before and after ether inhalation. Other four groups (OVX control, sham and lesioned, and OVE) were perfused for glucocorticoid receptor (GR) immunocytochemistry in hippocampal CA1 neurons and paraventricular nucleus (PVN). Estradiol replacement decreased while LC lesions increased stress-induced corticosterone secretion. The effect of LC lesion was potentiated with the removal of ovarian steroids. Since GR expression of lesioned animals decreased in the hippocampus, but not in PVN, we suggest that the effect of LC lesion on corticosterone secretion could be due to a reduction in the efficiency of the negative feedback system in the CA1 neurons. However, this mechanism is not involved in the estradiol modulation on corticosteroid secretion, as no change in GR expression was observed in estradiol-treated animals.

Role of locus coeruleus heme oxygenase-carbon monoxide-cGMP pathway during hypothermic response to restraint

Central heme oxigenase-carbon monoxide (HO-CO) pathway has been shown to play a pyretic role in the thermoregulatory response to restraint. However, the specific site in the central nervous system where CO may act modulating this response remains unclear. LC is rich not only in sGC but also in heme oxygenase (HO; the enzyme that catalyses the metabolism of heme to CO, along with biliverdin and free iron). Therefore, the possible role of the HO-CO-cGMP pathway in the restraint-induced-hypothermia by LC neurons was investigated. Body temperature dropped about 0.7 degrees C during restraint. ZnDPBG (a HO inhibitor; 5 nmol, intra-LC) prevented the hypothermic response during restraint. Conversely, induction of the HO pathway in the LC with heme-lysinate (7.6 nmol, intra-LC) intensified the hypothermic response to restraint, and this effect was prevented by pretreatment with ODQ (a sGC inhibitor; given intracerebroventricularly, 1.3 nmol). Taken together, these data suggest that CO in the LC produced by the HO pathway and acting via cGMP is implicated in thermal responses to restraint. (C) 2007 Elsevier Inc. All rights reserved.

Effect of cyhalothrin on Ehrlich tumor growth and macrophage activity in mice

Cyhalothrin, a pyrethroid insecticide, induces stress-like symptoms, increases c-fos immunoreactivity in the paraventricular nucleus of the hypothalamus, and decreases innate immune responses in laboratory animals. Macrophages are key elements in cellular immune responses and operate at the tumor-host interface. This study investigated the relationship among cyhalothrin effects on Ehrlich tumor growth, serum corticosterone levels and peritoneal macrophage activity in mice. Three experiments were done with 10 experimental (single gavage administration of 3.0 mg/kg cyhalothrin daily for 7 days) and 10 control (single gavage administration of 1.0 mL/kg vehicle of cyhalothrin preparation daily for 7 days) isogenic BALB/c mice in each experiment. Cyhalothrin i) increased Ehrlich ascitic tumor growth after ip administration of 5.0 x 106 tumor cells, i.e., ascitic fluid volume (control = 1.97 ± 0.39 mL and experimental = 2.71 ± 0.92 mL; P < 0.05), concentration of tumor cells/mL in the ascitic fluid (control = 111.95 ± 16.73 x 106 and experimental = 144.60 ± 33.18 x 106; P < 0.05), and total number of tumor cells in the ascitic fluid (control = 226.91 ± 43.22 x 106 and experimental = 349.40 ± 106.38 x 106; P < 0.05); ii) increased serum corticosterone levels (control = 200.0 ± 48.3 ng/mL and experimental = 420.0 ± 75.5 ng/mL; P < 0.05), and iii) decreased the intensity of macrophage phagocytosis (control = 132.3 ± 19.7 and experimental = 116.2 ± 4.6; P < 0.05) and oxidative burst (control = 173.7 ± 40.8 and experimental= 99.58 ± 41.7; P < 0.05) in vitro in the presence of Staphylococcus aureus. These data provide evidence that cyhalothrin simultaneously alters host resistance to Ehrlich tumor growth, hypothalamic-pituitary-adrenocortical (HPA) axis function, and peritoneal macrophage activity. The results are discussed in terms of data suggesting a link between stress, HPA axis activation and resistance to tumor growth.

Depressão, antidepressivos e sistema imune: um novo olhar sobre um velho problema

CONTEXTO: A hipótese monoaminérgica da depressão não responde a uma série de questões, tais como "quais as causas dos distúrbios monoaminérgicos?" e "como explicar uma taxa de 30% de refratariedade aos antidepressivos?". Sendo assim, outras teorias têm sido propostas, entre elas, aquelas que enfocam as participações dos sistemas imune e endócrino. OBJETIVOS: Analisar criticamente o papel do sistema de resposta imunoinflamatória na depressão e discutir a interação dos antidepressivos com esse sistema, tanto do ponto de vista básico como clínico. MÉTODOS: Realizou-se pesquisa bibliográfica utilizando-se as bases de dados MedLine e SciELO. RESULTADOS: Pacientes vítimas de estresse crônico e depressão apresentam ativação das respostas imunoinflamatórias e do eixo hipotálamo-hipófise-adrenal, os quais, direta ou indiretamente, influenciam a neurotransmissão. Nesse sentido, a utilização de antidepressivos não apenas aumenta a disponibilidade de neurotransmissores na fenda sináptica, mas também induz mudança do padrão de resposta imune Th1 - pró-inflamatório - para o Th2, que é antiinflamatório. Além disso, sabe-se que pacientes não responsivos aos antidepressivos possuem o sistema imuneinflamatório mais ativo. No entanto, há uma série de dados controversos na literatura, havendo indícios de um perfil imune diferente de acordo com o tipo de depressão. CONCLUSÕES: A compreensão de aspectos neuroimunes presentes na depressão poderia contribuir para um melhor entendimento das bases biológicas desse transtorno e, possivelmente, para novas perspectivas na busca de uma terapêutica mais efetiva.

Nutraceuticals in reproduction of bulls and stallions

The industry has made available in the market a series of substances (nutraceuticals) which intent would be to optimize the use of nutrients in some metabolic paths, influencing positively reproductive performance in animals. However, the response to the use of nutraceuticals varies according to the animal. As the organism is highly complex and in order to achieve a perfect activity of the hypothalamic-pituitary-gonadal axis, an ideal interaction in molecular basis is needed, where the nutraceuticals can have their direct action. The aim of this study was to review the function and research results using the main nutraceuticals (β carotene, vitamin A, L-carnitine, omegas 3, 6 and 9 and Gamma-oryzanol) on reproductive characteristics of bulls and stallions.

Melatonin reduces LH, 17 beta-estradiol and induces differential regulation of sex steroid receptors in reproductive tissues during rat ovulation

Background: Melatonin is associated with direct or indirect actions upon female reproductive function. However, its effects on sex hormones and steroid receptors during ovulation are not clearly defined. This study aimed to verify whether exposure to long-term melatonin is able to cause reproductive hormonal disturbances as well as their role on sex steroid receptors in the rat ovary, oviduct and uterus during ovulation. Methods: Twenty-four adult Wistar rats, 60 days old (+/-250 g) were randomly divided into two groups. Control group (Co): received 0.9% NaCl 0.3 mL + 95% ethanol 0.04 mL as vehicle; Melatonin-treated group (MEL): received vehicle + melatonin [ 100 mu g/100 g BW/day] both intraperitoneally during 60 days. All animals were euthanized by decapitation during the morning estrus at 4 a. m. Results: Melatonin significantly reduced the plasma levels of LH and 17 beta-estradiol, while urinary 6-sulfatoximelatonin (STM) was increased at the morning estrus. In addition, melatonin promoted differential regulation of the estrogen receptor (ER), progesterone receptor (PR), androgen receptor (AR) and melatonin receptor (MTR) along the reproductive tissues. In ovary, melatonin induced a down-regulation of ER-alpha and PRB levels. Conversely, it was observed that PRA and MT1R were up-regulated. In oviduct, AR and ER-alpha levels were down-regulated, in contrast to high expression of both PRA and PRB. Finally, the ER-beta and PRB levels were down-regulated in uterus tissue and only MT1R was up-regulated. Conclusions: We suggest that melatonin partially suppress the hypothalamus-pituitary-ovarian axis, in addition, it induces differential regulation of sex steroid receptors in the ovary, oviduct and uterus during ovulation.