Influence of substitutive ovarian steroids in the nuclear and cell body volumes of neurons in the posterodorsal medial amygdala of adult ovariectomized female rats

The volumes of the neuronal nucleus and the cell body in the left posterodorsal medial amygdala (MePD) of adult ovariectomized (OVX) female rats submitted to different hormonal therapies were studied here, aiming to reveal possible influence of substitutive sex steroids in these morphological parameters. One week following ovariectomy and at the end of treatments, brains were cut to semi-thin sections (1 μm) and stained with 1% toluidine blue for stereological estimations, carried out using the Cavalieri method and the technique of point counting. Both the volume of the neuronal nucleus and the soma showed a statistically significant difference when comparing the data among OVX females treated with vehicle (V), estradiol (EB) alone, EB plus progesterone (EB + P) or P alone [n = 5 rats in each group; one-way ANOVA test, P < 0.01 in both cases]. The Tukey test showed that OVX and EB + P treated females had higher mean neuronal nucleus and somatic volumes when compared to V (P < 0.01) or EB alone (P < 0.01). Also, OVX females treated with P alone showed larger mean neuronal nucleus and somatic volumes when compared to V (P < 0.05). These results suggest that the neuronal nucleus and the somatic volumes can be modulated by substitutive ovarian hormones administered to OVX females, for which P can lead to higher results. These findings reveal additional epigenetic actions of the sex steroids in the MePD and new neuronal morphological features in adult female rats.     

Endogenous CGRP protects retinal cells against stress induced apoptosis in rats

Acute stress can provoke apoptosis of the retina cells, and up-regulation of calcitonin gene related peptide (CGRP) in retina. However the role of CGRP in the pathology of the stress induced apoptosis of the retina cells is still elusive. The aim of this study was to investigate the endogenous of CGRP on retinal cell apoptosis induced by the stress of acute myocardial infarction induced by permanent coronary artery occlusion (CAO) in rats. The acute myocardial infarction model was established by ligating the left anterior descending branch of coronary artery in male Sprague-Dawley rats. The rats were randomized into two groups, the CGRP_8-37 group and a control group, pretreated with CGRP_8-37 (10⁻⁷ mol/L, 1 μL/g, intravenously injected), a specific antagonist of CGRP receptor, and 0.9% saline respectively, at 15 min prior to the CAO. The samples of the retina were collected at 3 h of CAO for the assays of TUNEL and caspase-3 activity respectively. The total apoptosis ratio of retinal cells in CGRP_8-37 group was significantly higher than that in the control group (P < 0.05). The capase-3 activity was significantly greater in the CGRP_8-37 group, compared with the control group (P < 0.05) at 3 h of CAO. The vacuolar degeneration of retinal ganglion cells was observed in the CAO animals. The results suggest that the endogenous CGRP may play a protective role in the retinal cell apoptosis induced by the stress of acute myocardial infarction.     

Differential alterations of GABA(A) receptor (α1, β2, γ2 subunit) expression and increased seizure susceptibility in rat offspring from morphine-addicted mothers: beneficial effect of dextromethorphan

Recent study demonstrated a close relationship between cerebellum atrophy and symptom severity of pediatric maltreatment-related posttraumatic stress disorder (PTSD). It has also been known that females are more vulnerable than males in developing anxiety disorders after exposure to traumatic stress. The mechanisms are unknown. Because cannabinoid receptors (CB₁ and CB₂) are neuroprotective and highly expressed in the cerebellum, we investigated cerebellar CB expression in stressed rats. Young male and female Sprague-Dawley rats were given 40 unpredictable electric tail-shocks for 2 h daily on 3 consecutive days. CB₁ and CB₂ mRNA and protein levels in rat cerebellum and brain stem were determined using quantitative real-time PCR and Western blot, respectively. Two-way ANOVA revealed significant gender and stress effects on cerebellar CB₁ mRNA expression, with females and non-stressed rats exhibiting higher CB₁ mRNA levels than the males (3 fold, p < 0.01) and stressed rats (30%, p < 0.01), respectively. CB₁ and CB₂ mRNA levels in brain stem were also greater in female rats than males (p < 0.01, p < 0.05, respectively). Repeated stress increased the level of phosphorylated CB₁ receptors, the inactivated CB₁, in rat cerebellum (p < 0.01), particularly in female rats as revealed by the significant gender × stress interaction. Thus, repeated severe stress caused greater CB₁ mRNA suppression and CB₁ receptor phosphorylation in female cerebellum that could lead to increased susceptibility to stress-related anxiety disorders including PTSD.     

Expression of calcitonin gene-related peptide type 1 receptor mRNA and their activity-modifying proteins in the rat nucleus accumbens

The calcitonin receptor-like receptor (CRLR) and the orphan receptor RDC-1 have been proposed to be calcitonin gene-related peptide type 1 (CGRP1) receptors, and receptor activity-modifying proteins (RAMPs) determine the ligand specificity of CRLR. Coexpression of RAMP1 and CRLR resulted in functional CGRP1 receptors; the complex of RAMP2 or RAMP3 and CRLR created functional adrenomedullin receptor. Although high levels of CGRP binding sites in the nucleus accumbens have been reported, little is known about the expression of these novel CGRP receptors. In the present study, we used real-time quantitative RT-PCR to detect and quantitate the relative expression of CGRP, CRLR, RAMP1-3 and RDC-1 in the nucleus accumbens of intact rats and rats with inflammation. Our results demonstrate that CGRP, CRLR, RAMP1 and RAMP2 exist in the nucleus accumbens of intact rats, and that they were significantly upregulated in rats with inflammation. In contrast, no expression was detected for RDC-1 and RAMP3. These findings indicated a functional role for CGRP and its receptors in inflammation and pain modulation.     

Different responses of nitric oxide synthase inhibition on morphine-induced antinociception in male and female rats

The roles of gonadal hormones and nitric oxide on pain perception and their interaction have been widely investigated. In the present study the chronic effect of l-NAME (NOS inhibitor) on morphine-induced antinociception in male and female rats was investigated. Forty rats were divided into four groups: (1) female (2) female-LN (3) male (4) and male-LN. The animals of groups 2 and 4 received daily injection of l-NAME (10 mg/kg) during 3 weeks. The animals of control groups 1 and 3 received 2 ml/kg saline instead of l-NAME. Finally, all animals were tested on the hot plate test (52 ± 0.2 °C; Cut-off 80 s) to evaluate the antinociceptive effects of morphine. The hot plate test was performed for base record 15 min before the injection of morphine (10 mg/kg; s.c.) and consequently it was repeated every 15 min after the injection. There were no significant differences in baseline latencies among all groups. Reaction times after injection of morphine in female-LN were higher than in the female control group (p < 0.01). There was, however, no significant difference between male control and male-LN groups. Reaction times in the female-LN group were significantly higher than in the male-LN group. Reaction times after injection of morphine in the male group was longer than in the female group (p < 0.01). It is concluded that sex hormones such as testosterone and estrogen have a role in pain perception and analgesia. NO has a modulatory effects on functions of sex hormones in pain perception and analgesic effects of opioids.     

Estradiol reduces anxiety- and depression-like behavior of aged female mice

Beneficial effects of the ovarian steroid, 17β-estradiol (E₂), for affective behavior have been reported in young individuals, but less is known about the effects of E₂ among older individuals, and the capacity of older individuals to respond to E₂ following its decline. In the present study, the effects of acute E₂ administration to aged mice for anxiety-like and depression-like behaviors were investigated. Intact female C57BL/6 mice (N = 18) that were approximately 24 months old were administered vehicle (sesame oil, n = 9) or E₂ (10 μg, n = 9) subcutaneously 1 h prior to behavioral testing. Mice were tested for anxiety-like behavior (open field, elevated plus maze, mirror chamber, light-dark transition task, Vogel conflict task) and depression-like behavior (forced swim task). To assess the role of general motor behavior and coordination in these aged mice, performance in an activity monitor and rotarod task, and total entries made in tasks (open field, elevated plus maze, light-dark transition task) were determined. Mice administered E₂, compared to vehicle, demonstrated anti-anxiety behavior in the open field, mirror chamber, and light-dark transition task, and anti-depressive-like behavior in the forced swim task. E₂ also tended to have anti-anxiety effects in the elevated plus maze and Vogel task compared to vehicle administration, but these effects did not reach statistical significance. E₂ did not alter motor behavior and/or coordination in the activity monitor, open field, or rotarod tasks. Thus, an acute E₂ regimen produced specific anti-anxiety and anti-depressant effects, independent of effects on motor behavior, when administered to aged female C57BL/6 mice.     

Involvement of CGRP and CGRPl receptor in nociception in the basolateral nucleus of amygdala of rats

The present study was performed to investigate the role of calcitonin gene-related peptide (CGRP) and its receptor in nociception in the basolateral nucleus of amygdala (BLA) of rats. Hindpaw withdrawal latencies (HWLs) to noxious thermal and mechanical stimulations were measured by hot plate and Randall Selitto tests. The HWL to both thermal and mechanical stimulations increased significantly after intra-BLA administration of 1.0 or 2.0 nmol CGRP, but not 0.5 nmol, indicating that CGRP plays an anti-nociceptive role in BLA of rats. The anti-nociceptive effect of 1.0 nmol CGRP was blocked significantly by administration of 1.0 or 2.0 nmol CGRP8-37, a selective antagonist of CGRP1 receptor, which suggests that the anti-nociceptive effect of CGRP is mediated by the CGRP1 receptor. Taken together, the results indicate that both CGRP and CGRP1 receptor play important roles in nociceptive modulation in the BLA of rats.     

Anxiety-like behavior in weanling and young adult male and female malnourished rats

The present study determined whether protein-calorie malnutrition alters anxiety-like behavior in weanling and young adult, male and female malnourished rats. On the day of birth, litters of Wistar rats were divided into Control (C) and Malnutrition (M) groups. In the C group, litters were fed by dams receiving ad libitum lab chow, whereas in the M group, litters were fed by dams receiving 40% of the total amount of the diet offered to dams in the C group. After weaning (PND21) until PND50, animals received the same food as theirs mothers (i.e., ad libitum access in the C group and 40% of the C group food in the M group). On PND21 and PND50, independent C (male [CM] and female [CF]) and M (male [MM] and female [MF]) groups were exposed to the elevated T-maze. The time taken to withdraw four paws from this arm was recorded (baseline latency [BL]). The same measurement was repeated twice at 30 s intervals (avoidance trial 1 [AT1] and avoidance 2 [AT2]). The cutoff time in each trial was 300 s. ANOVA indicated a four-way age × diet × sex × trials interaction. Post hoc comparisons revealed that PND50 rats had a lower BL and AT1 latency compared with PND21 rats. Training increased both AT1 and AT2 latencies compared with BL in both the CM and CF groups. Weanling malnourished rats exhibited reduced anxiety-like behavior and young adult male rats presented less anxiety-like behavior than young adult female rats in this experimental model.     

Increased cutaneous NGF and CGRP-labelled trkA-positive intra-epidermal nerve fibres in rat diabetic skin

In this study we have determined the amount of Nerve Growth Factor (NGF) and the innervation density of the glabrous hindpaw skin of diabetic rats (n = 4) and controls (n = 3). The proportion of intra-epidermal nerve fibres (IENF) expressing the high affinity NGF receptor (trkA) and calcitonin gene-related peptide (CGRP) were also determined. Four weeks after induction of diabetes by intraperitoneal streptozotocin injection skin was analyzed for: (i) NGF content using ELISA and (ii) the innervation density of peptidergic afferents that also expressed trkA using immunocytochemistry. NGF levels were approximately three-fold higher in diabetic skin compared to controls (diabetic: 134.7 ± 24.0 (SD) pg ml⁻¹, control: 42.7 ± 21.5 pg ml⁻¹, p = 0.002). As expected there was a significant reduction in IENF density in diabetic skin (2.7 ± 1.3 fibres mm⁻¹) compared to controls (6.9 ± 1.5 fibres mm⁻¹; p = 0.01). In diabetic rats there was no significant difference in the proportion of trkA-labelled IENF (diabetic 74 ± 21%; control 83 ± 15%, p = 0.6), but significantly more trkA-positive IENF were also labelled by CGRP antibodies in diabetic skin compared to controls (diabetic 89 ± 22%; control 38 ± 2%, p = 0.03). These data suggest that in diabetes the upregulation of cutaneous NGF may ‘over-troph’ the surviving axons, increasing CGRP labelling, which may be important in the aetiology of painful diabetic neuropathy.     

Formalin-induced nociceptive behavior and c-Fos expression in middle-aged female rats

The impact of the estrous cycle on the nociceptive response in middle-aged female rats was assessed using the formalin test and c-Fos immunoreactivity as a marker of neural activation. Young (2-month-old) and middle-aged (11-month-old) rats were examined, dividing the middle-aged rats into two groups based on their estrous cycle: regular 4-day estrous cycle and irregular estrous cycle. The right hind paw was subcutaneously injected with 50 μl of 2% formalin or saline as a control. Behavioral changes were observed for 1 h. Cycling rats were used during proestrus. Middle-aged female rats had a significantly higher score for nociceptive behavior compared to young rats, irrespective of estrous cyclicity, which suggests that aging, not the ability to maintain estrous cyclicity, causes hypersensitivity to the formalin injection. Immunohistochemical analysis found that the brain response to formalin injection was also more sensitive in middle-aged rats than young rats; a significant increase in the number of c-Fos immunoreactive cells was found in the ventral portion of the lateral septum of middle-aged rats injected with formalin compared to young and middle-aged rats injected with saline, irrespective of estrous cyclicity. Based on these results, we conclude that the sensitivity to painful stimuli in middle-aged female rats, which are in a neuroendocrine state similar to pre- and peri-menopausal women, is associated with age and not affected by reproductive ability.     

Serotonergic receptor upregulation in cerebral cortex and down regulation in brainstem of streptozotocin induced diabetic rats: Antagonism by pyridoxine and insulin

Insulin secretion and glucose homeostasis is implicated through serotonergic function. Pyridoxine is involved in decarboxylation step in synthesis of serotonin. The present study was carried out to find the role of insulin in combination with pyridoxine on the concentrations of 5-HT and 5-HIAA, 5-HT receptor binding, 5-HTT gene expression and immunohistochemistry studies in the cerebral cortex and brainstem of streptozotocin induced diabetic rats. 5-HT content showed a significant decrease with a significant increase in 5-HIAA in cerebral cortex (p < 0.01) and brain stem (p < 0.001) in diabetic rats. 5-HT receptor binding parameters, B_max and K_d, showed a significant decrease (p < 0.001) in diabetic rats in cerebral cortex whereas in brainstem it showed a significant increase (p < 0.001) compared to control. Gene expression studies of 5-HTT in cerebral cortex showed a significant down regulation (p < 0.001) and in brainstem an upregulation (p < 0.001) in diabetic rats compared to control. Insulin and pyridoxine treatment to diabetic rats reversed the 5-HT content, B_max, K_d and gene expression of 5-HTT confirmed by immunohistochemistry studies in cerebral cortex and brainstem to near control. Thus our results suggest that pyridoxine along with insulin has a role in the regulation of insulin synthesis and release through serotonergic function which has clinical significance in the management of diabetes.     

Differential and cell-specific expression of calcitonin receptor-like receptor and receptor activity modifying proteins in the human uterus.

The calcitonin receptor-like receptor (CRLR) can function as a receptor for either calcitonin gene-related peptide (CGRP) or adrenomedullin (AM), depending upon co-expression with members of a novel family of receptor activity-modifying proteins (RAMP). RAMP1 presents the CRLR at the cell surface as a CGRP/AM receptor. RAMP2- and RAMP3-transported CRLR receptors act as AM-specific receptors. However, it is still unknown if this signalling system operates in vivo. Of particular interest is the uterus, where both peptides and their binding sites are known to be present and where both mitogenic and vasodilatory responses to AM and CGRP have been demonstrated. In this study, we examined whether CRLR and RAMP are co-expressed in the same populations of cells in human uterine tissue. Analysis by in-situ hybridization and immunocytochemistry revealed a heterogeneous and cell type-specific distribution of components of this AM/CGRP signalling system. Adrenomedullin mRNA was expressed and evenly distributed across all cell types. CRLR mRNA was predominantly found in blood vessels. RAMP1 expression was specific to myometrial myocytes and vascular smooth muscle cells in uterine arteries. RAMP2 and RAMP3 mRNA were not detectable by in-situ hybridization. The pattern of differential and cell-specific expression of CRLR and RAMP suggests the involvement of CRLR/RAMP1 in the processes of vasodilation, smooth muscle relaxation and angiogenesis in response to AM and CGRP in the human uterus, but also indicates that other receptors may be implicated.     

Decreased opioid analgesia in weanling rats exposed to endothelin-1 during infancy

Endothelin-1 produces spontaneous nociceptive-associated behaviors that are modulated by the peripheral opioid system. The present study tests the hypothesis that single or repeated exposure to endothelin-1 during infancy decreases opioid analgesia in weanling rats. Morphine analgesia was measured in male and female postnatal day 21 rats following intraplantar endothelin-1 on postnatal day 7, or 11 or both days 7 and 11. In males, exposure to endothelin-1 on postnatal day 11 or both days 7 and 11 produced a statistically significant decrease in morphine analgesia (EC₅₀ = 0.902 and 1.326 mg/kg, respectively) compared to control (EC₅₀ = 0.486 mg/kg). Similarly in females, exposure to endothelin-1 on postnatal day 11 or both days 7 and 11 produced a statistically significant decrease in morphine analgesia (EC₅₀ = 1.367 and 1.226 mg/kg, respectively) compared to control (EC₅₀ = 0.468 mg/kg). In addition, females exposed to endothelin-1 on postnatal day 7 exhibited an intermediate decrease in morphine analgesia with an EC₅₀ of 0.752 mg/kg. In males, exposure to endothelin-1 decreased mu opioid receptor expression without changing endothelin-A receptor or endothelin-B receptor expression in the hindpaw skin. In contrast, in females, exposure to endothelin-1 increased expression of both endothelin receptors and the mu opioid receptor in hindpaw skin. These findings suggest a sex-difference in the window of vulnerability and the mechanism by which an acute nociceptive event can induce morphine tolerance.     

Steroid Sex Hormones and Macrophage Function: Modulation of Reactive Oxygen Intermediates and Nitrite Release

PROBLEM: In general, females have a more active immune response than do males. The effects of female sex hormones on lymphocytes have been studied extensively but their effects on macrophages are poorly understood. METHOD: In this study, peritoneal macrophages (M0) obtained from male rats were treated in vitro with estradiol (E₂), progesterone (P), testosterone (TS), or hydrocortisone (HC) and their effects on superoxide, hydrogen peroxide, and nitrite release determined. RESULTS: At concentrations between 10^?10 and 10^?9 M, female and male sex hormones had no significant effect on superoxide release but, at concentrations above or below that range, these hormones stimulated the release of these reactive oxygen intermediates (ROI). In contrast, M0 treated with HC generally exhibited either unaltered or reduced ROI release. CONCLUSIONS: These findings suggest that female sex hormones regulate ROI release by Mø in a manner not entirely shared by other steroid hormones. At most concentrations used, E₂, P, TS, and HC significantly inhibited nitrite release by Mø. However, with 10^?10 M of E₂ or 10^?9M of P, nitrite release by Mø was not affected. In the presence of anti-TNF antibody, the amounts of superoxide and hydrogen peroxide release were moderately reduced but nitrite release was dramatically inhibited. The sensitivity of Mø to variations in the concentrations of female sex hormones may contribute to gender-related differences in the immune response.     

The endocannabinoid transport inhibitor AM404 modulates nociception in cholestasis

Cholestasis is associated with increased activity of the endogenous opioid system that results in analgesia. Endocannabinoid system can reduce pain sensitivity. Considering the interaction that has been shown between the endogenous opioid and endocannabinoid systems in nociception processing, we studied the effect of AM404, an endocannabinoid transport inhibitor, on modulation of nociception in cholestasis, a model of elevated endogenous opioid tone. Cholestasis was induced by ligation of the main bile duct using two ligatures and transection of the duct at the midpoint between them. A significant increase (P < 0.01) in TF was observed in cholestatic rats compared to unoperated and sham rats. AM404 (10 mg/kg, i.p.) significantly increased TFL at 5, 30 min but not 60 min after injection in cholestatic animals compared to the vehicle treated cholestatic group (P < 0.05, P < 0.001, respectively). AM404 injection to unoperated and sham rats did not alter baseline TFL. The effect of AM404 in cholestatic rats was blocked by co-administration of a CB₁ receptor antagonist, AM251 (1 mg/kg, i.p.) but not by the CB2 receptor antagonist, SR144528 (1 mg/kg, i.p.). Naloxone injection blocked the antinociception induced by cholestasis in bile duct ligated group. Antinociception produced by injection of AM404 in cholestatics was also attenuated by co-administration of naloxone. These data show that AM404 potentiates antinociception induced by cholestasis and indicate that there are possible interactions between opioid and cannabinoid systems in this experimental model of elevated endogenous opioid tone. The inhibitory effects of AM404 in this model are mediated by cannabinoid CB₁ and not CB₂ receptors.     

Differential hippocampal pharmacokinetics of phenobarbital and carbamazepine in repetitive seizures induced by 3-mercaptopropionic acid

Previous evidence has shown that chronic 3-mercaptopropionic acid (MP) administration induced brain P-glycoprotein (P-gp) overexpression altering target site accumulation of phenytoin. The aim of the present work was to assess the involvement of P-glycoprotein in carbamazepine and phenobarbital hippocampal pharmacokinetics in an experimental model of epilepsy, induced by repetitive MP administration. Seizures were induced in Wistar rats by injection of MP (45 mg kg⁻¹, i.p.) during 10 days. Control rats (C) were injected with saline solution. In order to monitor extracellular brain antiepileptic levels, a concentric probe was inserted into the hippocampus. Animals were administered with carbamazepine (10 mg kg⁻¹, i.v.) or phenobarbital (20 mg kg⁻¹, i.v.) 30 min after intraperitoneal administration of vehicle or nimodipine (2 mg kg⁻¹), a well known P-glycoprotein inhibitor. No differences were found in hippocampal concentrations of carbamazepine comparing all groups. In vehicle pre-treated rats, hippocampal phenobarbital concentrations were lower in MP (maximal concentration, C_max: 6.0 ± 0.6 μg ml⁻¹, p < 0.05) than in C animals (C_max: 9.4 ± 0.9 μg ml⁻¹). Control rats pre-treated with nimodipine showed similar results (C_max: 10.7 ± 0.6 μg ml⁻¹) than those pre-treated with vehicle. Nimodipine pre-treatment in MP rats enhanced hippocampal phenobarbital concentrations (C_max: 10.2 ± 1.0 μg ml⁻¹, p < 0.05) as compared with vehicle pre-treatment.     

Regulatory role of 1, 25-dihydroxyvitamin D3 and vitamin D receptor gene variants on intracellular granzyme A expression in pulmonary tuberculosis

Vitamin D receptor (VDR) genotypes have been shown to be associated with differential susceptibility or resistance to tuberculosis. The influence of FokI, BsmI, ApaI and TaqI variants of VDR gene on 1, 25(OH)₂ D₃ modulated granzyme A expression of cytotoxic lymphocytes induced by culture filtrate antigen (CFA) of Mycobacterium tuberculosis was studied in 40 pulmonary tuberculosis (PTB) patients and 49 normal healthy subjects (NHS) by flow cytometry. In both the study groups, addition of 1, 25(OH)₂ D₃ (10^− 7M) significantly reduced the percentage of granzyme A positive cells in both unstimulated (NHS, p < 0.0001; PTB, p = 0.02) and stimulated culture conditions (CFA, NHS, p < 0.0001; PTB, p = 0.0001) which correlated positively with the IFN-γ levels (unstimulated, p = 0.01; CFA stimulated, p = 0.004) in NHS. The ApaI aa genotype and bbaaTT extended genotype were associated with a significantly decreased percentage of granzyme A positive cells in NHS (p < 0.05). Our results suggest that 1, 25(OH)₂ D₃ suppresses granzyme A probably by down-regulating Th1 cytokine response. Moreover, the VDR gene variants might regulate cytotoxic T-cell response via 1, 25(OH)₂ D₃ mediated suppression of granzyme A expression in tuberculosis.     

Estrous cycle in ob/ob and ovariectomized female mice and its relation with estrogen and leptin

Hormones like leptin and estrogen have been suggested to increase energy expenditure and modulate estrous cycle. The aim of this study was to investigate the stages of estrous cycle in mouse models with contrasting leptin and estrogen levels. Estrous cycle of wild type (WT), WT ovariectomized (OVX), ob/ob and ob/ob OVX was observed by obtaining vaginal smear and staining with Papanicolaou (PAP) procedure. Quantitative analysis showed cellular morphology and predominance of cellular content across the estrous cycle. Microscopical and quantitative counts showed a 4-5 day regular cycle in WT mouse, WTOVX were acyclic, infertile and hardly showed any cells, ob/ob and ob/ob OVX were both acyclic, infertile and were at persistent estrous or persistent metaestrous phase. Enzyme-Immunometric Assay results showed that leptin levels were about 3 fold higher in WTOVX than WT mouse (p < 0.0001) with β-estradiol values being negligible in WTOVX. The β-estradiol levels for ob/ob and WT were similar. These results suggest that although leptin and estrogen play an important role in the estrous cycle, they are not the sole factor influencing the cycle. It is probable that in the absence of leptin and decrease in sex steroid hormones with increase in acyclicity, the central nervous system probably interprets the circulation as absence of energy stores and shuts down reproduction indicated by the changes in the estrous cycle.     

Hypothalamic serotonin-1A receptor binding measured by PET predicts the plasma level of dehydroepiandrosterone sulfate in healthy women

Serotonin modulates the activity of the hypothalamic–pituitary–adrenal (HPA) axis particularly via the serotonin-1A receptor (5-HT_1A). Therefore, the rationale of this positron emission tomography (PET) study was to investigate the influence of the 5-HT_1A receptor distribution in the human brain on plasma levels of dehydroepiandrosterone sulfate (DHEAS) and cortisol in vivo. Eighteen healthy female were measured with PET and the selective 5-HT_1A receptor radioligand [carbonyl-¹¹C]WAY-100635. Nine a priori defined brain regions (hypothalamus, orbitofrontal cortex, amygdala, hippocampus, anterior and posterior cingulate cortices, dorsal raphe nucleus, retrosplenial cortex, and insula) and the cerebellum (reference region) were delineated on coregistered MR images. DHEAS and cortisol plasma levels were collected by blood sampling in the morning of the PET day. Linear regression analysis of DHEAS plasma level as dependent variable and hypothalamic 5-HT_1A receptor binding potential (BP) as independent variable showed a highly significant association (r = .691, p = .002). The hypothalamic 5-HT_1A BP predicted 47.7% of the variability in DHEAS plasma levels. Regressions were borderline significant (p < .01, Bonferroni corrected threshold <.0056) between 5-HT_1A BP in the anterior cingulate and orbitofrontal cortices and free cortisol levels. No significant associations between DHEAS or cortisol and the 5-HT_1A receptor BP in other investigated brain regions were found. In conclusion, the serotonergic system may influence the DHEAS plasma level by modulating CRH and ACTH release via hypothalamic 5-HT_1A receptors as reported for cortisol before. As disturbances of the HPA axis as well as changes of the 5-HT_1A receptor distribution have been reported in affective disorders, future studies should focus on these interactions.     

Serotonergic system involvement in the inhibitory action of estrogen on induced sodium appetite in female rats

This study of the participation of the serotonergic system in the inhibitory effect of estrogen on induced sodium appetite in female rats explores sodium appetite induced by Furosemide and low sodium diet treatment (DEP) in normally cycling rats and in ovariectomized rats with and without estradiol replacement (OVX, OVX + E₂) . We also analyzed the neural activity of serotonergic neurons of the dorsal raphe nucleus (DRN) as well as the activity of other brain nuclei previously found to be involved in sodium and water balance in sodium depleted animals without access to the intake test. For this purpose, we examined the brain Fos, Fos-serotonin and Fos-vasopressin immunoreactivity patterns in diestrus (D), estrus (E), OVX and OVX + E₂ rats subjected to DEP.Female rats in E and OVX + E₂ exhibited a significant decrease in induced sodium intake compared with females in D and OVX. This estrogen-dependent inhibition on induced sodium appetite (approximately 50% reduction) can be correlated with changes in Fos activation observed in the organum vasculosum of the lamina terminalis (OVLT) and DRN, in response to sodium depletion. Given our previous observations in males, the expected sodium depletion-induced activity of the OVLT was found to be absent in OVX + E₂ females, while the usual inhibitory tonic activity of serotonergic neurons of the DRN, instead of decreasing after sodium depletion, increases or remains unchanged in OVX + E₂-DEP and E-DEP females, respectively.Regarding urinary water and sodium excretion 3 h after furosemide treatment, E-DEP and OVX + E₂-DEP animals excreted smaller volumes of more highly concentrated urine than depleted D and OVX rats. Twenty hours after sodium depletion, the same groups of animals also showed a significant increase in the number of Fos-AVP immunoreactive neurons within the supraoptic nucleus, compared with D-DEP.In summary, our results demonstrate an estrogen-dependent inhibition of induced sodium appetite in normally cycling rats and ovariectomized animals with estradiol replacement, which may involve an interaction between excitatory neurons of the OVLT and inhibitory serotonergic cells of the DRN. The main finding is thus serotonergic system involvement as a possible mechanism in the inhibitory action of estrogen on induced sodium appetite.