Estrogen alters c-Fos response to immobilization stress in the brain of ovariectomized rats

Pivotal role of orexin signaling in the posterior paraventricular nucleus of the thalamus during the stress-induced reinstatement of oxycodone-seeking behavior

BACKGROUND

The orexin (OX) system has received increasing interest as a potential target for treating substance use disorder. OX transmission in the posterior paraventricular nucleus of the thalamus (pPVT), an area activated by highly salient stimuli that are both reinforcing and aversive, mediates cue- and stress-induced reinstatement of reward-seeking behavior. Oral administration of suvorexant (SUV), a dual OX receptor (OXR) antagonist (DORA), selectively reduced conditioned reinstatement of oxycodone-seeking behavior and stress-induced reinstatement of alcohol-seeking behavior in dependent rats.

AIMS

This study tested whether OXR blockade in the pPVT with SUV reduces oxycodone or sweetened condensed milk (SCM) seeking elicited by conditioned cues or stress.

METHODS

Male Wistar rats were trained to self-administer oxycodone (0.15 mg/kg, i.v., 8 h/day) or SCM (0.1 ml, 2:1 dilution [v/v], 30 min/day). After extinction, we tested the ability of intra-pPVT SUV (15 µg/0.5 µl) to prevent reinstatement of oxycodone or SCM seeking elicited by conditioned cues or footshock stress.

RESULTS

The rats acquired oxycodone and SCM self-administration, and oxycodone intake correlated with signs of physical opioid withdrawal, confirming dependence. Following extinction, the presentation of conditioned cues or footshock elicited reinstatement of oxycodone- and SCM-seeking behavior. Intra-pPVT SUV blocked stress-induced reinstatement of oxycodone seeking but not conditioned reinstatement of oxycodone or SCM seeking or stress-induced reinstatement of SCM seeking.

CONCLUSIONS

The results indicate that OXR signaling in the pPVT is critical for stress-induced reinstatement of oxycodone seeking, further corroborating OXRs as treatment targets for opioid use disorder.

Expanding the canon: An inclusive neurobiology of thalamic and subthalamic fear circuits

Appropriate expression of fear in the face of threats in the environment is essential for survival. The sustained expression of fear in the absence of threat signals is a central pathological feature of trauma- and anxiety-related disorders. Our understanding of the neural circuitry that controls fear inhibition coalesces around the amygdala, hippocampus, and prefrontal cortex. By discussing thalamic and sub-thalamic influences on fear-related learning and expression in this review, we suggest a more inclusive neurobiological framework that expands our canonical view of fear. First, we visit how fear-related learning and expression is influenced by the aforementioned canonical brain regions. Next, we review emerging data that shed light on new roles for thalamic and subthalamic nuclei in fear-related learning and expression. Then, we highlight how these neuroanatomical hubs can modulate fear via integration of sensory and salient stimuli, gating information flow and calibrating behavioral responses, as well as maintaining and updating memory representations. Finally, we propose that the presence of this thalamic and sub-thalamic neuroanatomy in parallel with the tripartite prefrontal cortex-amygdala-hippocampus circuit allows for dynamic modulation of information based on interoceptive and exteroceptive signals. This article is part of the Special Issue on "Fear, Anxiety and PTSD".

Upregulation of neuropeptide Y in cardiac sympathetic nerves induces stress (Takotsubo) cardiomyopathy

Substantial emotional or physical stress may lead to an imbalance in the brain, resulting in stress cardiomyopathy (SC) and transient left ventricular (LV) apical ballooning. Even though these conditions are severe, their precise underlying mechanisms remain unclear. Appropriate animal models are needed to elucidate the precise mechanisms. In this study, we established a new animal model of epilepsy-induced SC. The SC model showed an increased expression of the acute phase reaction protein, c-Fos, in the paraventricular hypothalamic nucleus (PVN), which is the sympathetic nerve center of the brain. Furthermore, we observed a significant upregulation of neuropeptide Y (NPY) expression in the left stellate ganglion (SG) and cardiac sympathetic nerves. NPY showed neither positive nor negative inotropic and chronotropic effects. On the contrary, NPY could interrupt β-adrenergic signaling in cardiomyocytes when exposure to NPY precedes exposure to noradrenaline. Moreover, its elimination in the left SG via siRNA treatment tended to reduce the incidence of SC. Thus, our results indicated that upstream sympathetic activation induced significant upregulation of NPY in the left SG and cardiac sympathetic nerves, resulting in cardiac dysfunctions like SC.

Ameliorating effect offluoxetine on tamoxifen-induced memory loss: The role of corticolimbic NMDA receptors and CREB/BDNF/cFos signaling pathways in rats

Tamoxifen-induced cognitive dysfunction may lead to fluoxetine consumption in patients with breast cancer. Since the brain mechanisms are unclear in tamoxifen/fluoxetine therapy, the blockade effect of hippocampal/amygdala/prefrontal cortical NMDA receptors was examined in fluoxetine/tamoxifen-induced memory retrieval. We also assessed the corticolimbic signaling pathways in memory retrieval under the drug treatment in adult male Wistar rats. Using the Western blot technique, the expression levels of the cAMP response element-binding protein (CREB), brain-derived neurotrophic factor (BDNF), and cFos were evaluated in the corticolimbic regions. The results showed that pre-test administration of fluoxetine (3 and 5 mg/kg, i.p.) improved tamoxifen-induced memory impairment in the passive avoidance learning task. Pre-test bilateral microinjection of D-AP5, a selective NMDA receptor antagonist, into the dorsal hippocampal CA1 regions and the central amygdala (CeA), but not the medial prefrontal cortex (mPFC), inhibited the improving effect of fluoxetine on tamoxifen response. It is important to note that the microinjection of D-AP5 into the different sites by itself did not affect memory retrieval. Memory retrieval increased the signaling pathway of pCREB/CREB/BDNF/cFos in the corticolimbic regions. Tamoxifen-induced memory impairment decreased the hippocampal/PFC BDNF level and the amygdala level of pCREB/CREB/cFos. The improving effect of fluoxetine on tamoxifen significantly increased the hippocampal/PFC expression levels of BDNF, the PFC/amygdala expression levels of cFos, and the ratio of pCREB/CREB in all targeted areas. Thus, NMDA receptors' activity in the different corticolimbic regions mediates fluoxetine/tamoxifen memory retrieval. The corticolimbic synaptic plasticity changes likely accompany the improving effect of fluoxetine on tamoxifen response.

Sex Differences in the Role of Neurexin 3α in Zoster Associated Pain

Varicella zoster virus (VZV) induces orofacial pain and female rats show greater pain than male rats. During the proestrus phase of the estrous cycle the VZV induce pain response is attenuated in female rats. A screen of gene expression changes in diestrus and proestrus female rats indicated neurexin 3α (Nrxn3α) was elevated in the central amygdala of proestrus rats vs. diestrus rats. GABAergic neurons descend from the central amygdala to the lateral parabrachial region and Nrxn3α is important for presynaptic γ-Aminobutyric acid (GABA) release. Thus, we hypothesized that the reduced orofacial pain in male rats and proestrus female rats is the result of increased Nrxn3α within the central amygdala that increases GABA release from axon terminals within the parabrachial and inhibits ascending pain signals. To test this hypothesis Nrxn3 α expression was knocked-down by infusing shRNA constructs in the central amygdala. Then GABA release in the parabrachial was quantitated concomitant with measuring the pain response. Results revealed that knockdown of Nrxn3α expression significantly increases the pain response in both male rats and proestrus female rats vs. diestrus rats. GABA release was significantly reduced in the parabrachial of male and proestrus female rats after Nrxn3α knockdown. Neuronal activity of excitatory neurons was significantly inhibited in the parabrachial after Nrxn3α knockdown. These results are consistent with the idea that Nrxn3 within the central amygdala controls VZV associated pain by regulating GABA release in the lateral parabrachial that then modulates ascending orofacial pain signals.

Influences of Stress and Sex on the Paraventricular Thalamus: Implications for Motivated Behavior

The paraventricular nucleus of the thalamus (PVT) is a critical neural hub for the regulation of a variety of motivated behaviors, integrating stress and reward information from environmental stimuli to guide discrete behaviors via several limbic projections. Neurons in the PVT are activated by acute and chronic stressors, however several roles of the PVT in behavior modulation emerge only following repeated stress exposure, pointing to a role for hypothalamic pituitary adrenal (HPA) axis modulation of PVT function. Further, there may be a reciprocal relationship between the PVT and HPA axis in which chronic stress-induced recruitment of the PVT elicits an additional role for the PVT to regulate motivated behavior by modulating HPA physiology and thus the neuroendocrine response to stress itself. This complex interaction may make the PVT and its role in influencing motivated behavior particularly susceptible to chronic stress-induced plasticity in the PVT, especially in females who display increased susceptibility to stress-induced maladaptive behaviors associated with neuropsychiatric diseases. Though literature is describing the sex-specific effects of acute and chronic stress exposure on HPA axis activation and motivated behaviors, the impact of sex on the role of the PVT in modulating the behavioral and neuroendocrine response to stress is less well established. Here, we review what is currently known regarding the acute and chronic stress-induced activation and behavioral role of the PVT in male and female rodents. We further explore stress hormone and neuropeptide signaling mechanisms by which the HPA axis and PVT interact and discuss the implications for sex-dependent effects of chronic stress on the PVT's role in motivated behaviors.

Reduced activity of GAD67 expressing cells in the reticular thalamus enhance thalamic excitatory activity and varicella zoster virus associated pain

Within the reticular thalamic nucleus neurons express gamma aminobutyric acid (GABA) and these cells project to the ventral posteromedial thalamic nucleus. When GABA activity decreases the activity of excitatory cells in the ventral posteromedial nucleus would be expected to increase. In this study, we addressed the hypothesis that attenuating GABAergic cells in the reticular thalamic nucleus increases excitatory activity in the ventral posteromedial nucleus increasing varicella zoster virus (VZV) associated pain in the orofacial region. Adeno-associated virus (AAV) was infused in the reticular thalamic nucleus of Gad1-Cre rats. This virus transduced a G inhibitory designer receptor exclusively activated by designer drugs (DREADD) gene that was Cre dependent. A dose of estradiol that was previously shown to reduce VZV pain and increase GABAergic activity was administered to castrated and ovariectomized rats. Previous studies suggest that estradiol attenuates herpes zoster pain by increasing the activity of inhibitory neurons and decreasing the activity of excitatory cells within the lateral thalamic region. The ventral posteromedial nucleus was infused with AAV containing a GCaMP6f expression construct. A glass lens was implanted for miniscope imaging. Our results show that the activity of GABA cells within the reticular thalamic region decreased with clozapine N-oxide treatment concomitant with increased calcium activity of excitatory cells in the ventral posteromedial nucleus and an increased orofacial pain response. The results suggest that estradiol attenuates herpes zoster pain by increasing the activity of inhibitory neurons within the reticular thalamus that then inhibit excitatory activity in ventral posteromedial nucleus causing a reduction in orofacial pain.

Sex differences in the effects of acute stress on cerebral glucose metabolism: A microPET study

Stress has been considered as a risk factor for the development and aggravation of several diseases. The hypothalamic-pituitary-adrenal axis (HPA) is one of the main actors for the stress response and homeostasis maintenance. Positron emission tomography (PET) has been used to evaluate neuronal activity and to study brain regions that may be related to the HPA axis response. Since neuroimaging is an important tool in detecting neuroendocrine-related changes, we used fluorodeoxyglucose-18 (¹⁸F-FDG) and positron emission microtomography (microPET) to evaluate sexual differences in the glucose brain metabolism after 10, 30 and 40 min of acute stress in Balb/c mice. We also investigated the effects of restraint stress in blood, liver and adrenal gland ¹⁸F-FDG biodistribution using a gamma counter. A decreased glucose uptake in the whole brain in both females and males was found. Additionally, there were time and sex-dependent alterations in the ¹⁸F-FDG uptake after restraint stress in specific brain regions, indicating that males could be more vulnerable to the short-term effects of acute stress. According to the gamma counter biodistribution, only females showed a significant decreased glucose uptake in the blood, liver and right adrenal after restraint stress. In addition, in comparisons between the sexes, males showed a decreased glucose uptake in the whole brain and in several brain regions compared to females. In conclusion, exposure to acute restraint stress resulted in significant decreased glucose metabolism in the brain, with particular effects in different regions and organs in a sex-specific manner.

Estradiol Acts in Lateral Thalamic Region to Attenuate Varicella Zoster Virus Associated Affective Pain

Varicella zoster virus (VZV) results in chicken pox and herpes zoster. Female rats show a higher level of herpes zoster associated pain than males, consistent with human studies. In this study, we addressed the novel hypothesis that sex difference in herpes zoster associated pain is due, in part, to estradiol modulating activity in the thalamus. To test this hypothesis a high and low physiological dose of estradiol was administered to castrated and ovariectomized rats and the affective pain response was measured after injection of VZV into the whisker pad. Thalamic infusion of the estrogen receptor antagonist ICI 182,780 concomitant with a high dose of estradiol addressed the role of estradiol binding to its receptor to effect pain. Phosphorylated extracellular signal-regulated protein kinase (pERK) positive cells were measured in excitatory (glutaminase positive) and inhibitory (glutamate decarboxylase 67 positive) cells of the lateral thalamic region. Our results show that a high dose of estradiol significantly reduced the pain response in both males and females. pERK significantly increased in excitatory cells after treatment with a low dose of estradiol and increased in inhibitory cells after treatment with a high dose of estradiol. Administration of ICI 182,780 significantly increased the pain response, reduced expression of GABA related genes in the thalamic region and significantly reduced the number of inhibitory cells expressing pERK. The results suggest that estradiol attenuates herpes zoster pain by increasing the activity of inhibitory neurons within the thalamus and that this reduction includes an estrogen receptor dependent mechanism.

Aromatase Derived Estradiol Within the Thalamus Modulates Pain Induced by Varicella Zoster Virus

Herpes zoster or shingles is the result of varicella zoster virus (VZV) infection and often results in chronic pain that lasts for months after visible symptoms subside. Testosterone often attenuates pain in males. Previous work demonstrates ovarian estrogen effects γ-aminobutyric acid (GABA) signaling in the thalamus, reducing pain but the role of testosterone within the thalamus is currently unknown. Because aromatase affects pain and is present in the thalamus we tested a hypothesis that testosterone converted to estrogen in the thalamus attenuates herpes zoster induced pain. To address this hypothesis, male Sprague-Dawley rats received whisker pad injection of either MeWo cells or MeWo cells containing VZV. To reduce aromatase derived estrogen in these animals we injected aromatase inhibitor letrozole systemically or infused it into the thalamus. To test if estrogen was working through the estrogen receptor (ER) agonist, 4, 4′, 4″-(4-Propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol (PPT) was infused concomitant with letrozole. Motivational and affective pain was measured after letrozole and/or PPT treatment. Vesicular GABA transporter (VGAT) is important in pain signaling. Because estrogen effects VGAT expression we measured its transcript and protein levels after letrozole treatment. Virus injection and letrozole significantly increased the pain response but thalamic infusion of PPT reduced zoster pain. Letrozole increased the number of thalamic neurons staining for phosphorylated ERK (pERK) but decreased VGAT expression. The results suggest in male rats aromatase derived estradiol interacts with the ER to increase VGAT expression and increase neuronal inhibition in the thalamus to attenuate VZV induced pain.

Comprehensive assessment of sex hormones in Takotsubo syndrome

BACKGROUND

The detailed pathomechanism of Takotsubo syndrome (TS) is still elusive. Due to the predominance of postmenopausal females, a potential role of sex hormones has been suggested. However, the limited available data are contradictory. The aim of this study was to comprehensively assess the role of sex hormone levels in a large cohort of TS patients.

METHODS

Serum samples of 57 female TS patients and 57 female patients with myocardial infarction (MI), matched for age (±2years) and repolarization disturbances were analyzed for estradiol (E2), estrone (E1), testosterone and androstenedione using liquid chromatography-tandem mass spectrometry.

RESULTS

There was no difference concerning the concentrations of E1 [pmol/l (IQR): 89.1 (62.5, 132.0) vs. 98.8 (63.3, 156.0), p=0,441], testosterone [nmol/l (IQR): 0.67 (0.46, 1.00) vs. 0.80 (0.49, 1.08), p=0.382] and androstenedione [nmol/l (IQR): 2.03 (1.57, 3.11) vs. 2.98 (1.48, 5.27), p=0.244] between female TS and MI patients. Regarding E2, the majority of patients demonstrated concentrations below the detection limit of 30pmol/l (TS: n=41/54, 75.9%; MI: n=32/53, 60.4%; p=0.078). The remaining individuals with detectable E2 concentrations did not show a significant difference between TS and MI patients [pmol/l (IQR): 40.5 (33.0, 53.3) vs. 54.1 (37.9, 60.9); p=0.20].

CONCLUSIONS

Altered sex hormone levels, especially an estradiol deficiency, could not be identified as a risk factor for TS.

Estrogen replacement attenuates stress-induced pressor responses through vasorelaxation via β2-adrenoceptors in peripheral arteries of ovariectomized rats

We examined whether chronic estrogen replacement has an inhibitory effect on stress-induced pressor responses via activation of β₂-adrenoceptor (AR) in peripheral arteries of ovariectomized rats. Female Wistar rats aged 9 wk were ovariectomized. After 4 wk, pellets containing either 17β-estradiol (E₂) or placebo (Pla) were subcutaneously implanted into the rats. After 4 wk of treatment, rats underwent cage-switch stress, and, in a separate experiment, a subset received an infusion of isoproterenol (ISO) with or without pretreatment with the β₁-AR blocker atenolol or the β₂-AR blocker butoxamine. In addition, the isolated mesenteric artery was used to assess the concentration-related relaxing responses to ISO and the β₁- or β₂-AR mRNA level. The cage-switch stress-induced pressor response was significantly attenuated in the E₂-treated group compared with the Pla-treated group. Pretreatment with atenolol reduced blood pressure responses in both groups. However, butoxamine enhanced the pressor response only in the E₂-treated group, resulting in no difference between the two groups. In addition, the intravenous ISO-induced depressor response was significantly enhanced in the E₂-treated group compared with the Pla-treated group. Furthermore, the difference in the depressor response was abolished by pretreatment with butoxamine but not by atenolol. In the isolated mesenteric artery, butoxamine caused a rightward shift in ISO-induced concentration-related relaxation in the E₂-treated group. The β₂-AR mRNA level in the mesenteric artery was higher in the E₂-treated group than in the Pla-treated group. These results suggest that estrogen replacement attenuated the stress-induced pressor response probably by suppressing vasoconstriction via activation of β₂-ARs in peripheral arteries of ovariectomized rats. NEW & NOTEWORTHY In this study, we show, for the first time, that estrogen replacement has an inhibitory effect on the psychological stress-induced pressor response through vasorelaxation via β₂-adrenoceptors, probably due to overexpression of β₂-adrenoceptor mRNA, in peripheral arteries of ovariectomized rats.

[Cardiac dysfunction secondary to an adrenergic storm or cardiomyopathy of stress among child victims of traumatism]

OBJECTIVE

To provide information specific to a catecholaminergic storm during a violent stress in children.

PATIENTS AND METHODS

Two clinical observations in children who suffered violent trauma.

FIRST CASE

a boy aged 12 years victim of a drowning in Stage 3 admitted to the pediatric intensive care 02.08.2015. He was intubated, ventilated, sedated with benzodiazepines and morphine. Cardiac exploration revealed a global hypokinesis with septal dyskinesia, a 45% FES offset a slight excess of ST, a troponin I to 31.46pg/mL NT-proBNB to 1291pg/mL. Dobutamine was set initially at 7 then 10 gamma/kg/min. The outcome was favorable on the heart level with improved SEF in 1 week.

SECOND CASE

13-year-old girl, victim of complete hanging, admitted on 06/08/2015 for a post-anoxic encephalopathy. Intubated, ventilated and sedated with morphine and benzodiazepines. Cardiac exploration showed septal hypokinesia with a 35% FES, a lengthening of the QT interval on the ECG, a troponin I in ultra 1.27μg/L, NT-proBNB to 215pg/mL. The child was put up 15 gamma dobutamine/kg/min. The evolution was marked by improved heart function without disturbance wall motion after 7 days.

CONCLUSION

Our 2 clinical cases following accidental trauma violating represent observations of a picture simulating a syndrome of Tako-Tsubo without anginal pain objectified as our 2 patients were sedated and ultrasound abnormalities returned to normal in less than a week.

Slow-pressor angiotensin II hypertension and concomitant dendritic NMDA receptor trafficking in estrogen receptor β-containing neurons of the mouse hypothalamic paraventricular nucleus are sex and age dependent

The incidence of hypertension increases after menopause. Similar to humans, "slow-pressor" doses of angiotensin II (AngII) increase blood pressure in young males, but not in young female mice. However, AngII increases blood pressure in aged female mice, paralleling reproductive hormonal changes. These changes could influence receptor trafficking in central cardiovascular circuits and contribute to hypertension. Increased postsynaptic N-methyl-D-aspartate (NMDA) receptor activity in the hypothalamic paraventricular nucleus (PVN) is crucial for the sympathoexcitation driving AngII hypertension. Estrogen receptors β (ERβs) are present in PVN neurons. We tested the hypothesis that changes in ovarian hormones with age promote susceptibility to AngII hypertension, and influence NMDA receptor NR1 subunit trafficking in ERβ-containing PVN neurons. Transgenic mice expressing enhanced green fluorescent protein (EGFP) in ERβ-containing cells were implanted with osmotic minipumps delivering AngII (600 ng/kg/min) or saline for 2 weeks. AngII increased blood pressure in 2-month-old males and 18-month-old females, but not in 2-month-old females. By electron microscopy, NR1-silver-intensified immunogold (SIG) was mainly in ERβ-EGFP dendrites. At baseline, NR1-SIG density was greater in 2-month-old females than in 2-month-old males or 18-month-old females. After AngII infusion, NR1-SIG density was decreased in 2-month-old females, but increased in 2-month-old males and 18-month-old females. These findings suggest that, in young female mice, NR1 density is decreased in ERβ-PVN dendrites thus reducing NMDA receptor activity and preventing hypertension. Conversely, in young males and aged females, NR1 density is upregulated in ERβ-PVN dendrites and ultimately leads to the neurohumoral dysfunction driving hypertension.

Ventilatory, metabolic, and thermal responses to hypercapnia in female rats: effects of estrous cycle, ovariectomy, and hormonal replacement

The aim of this study was to examine how estrous cycle, ovariectomy, and hormonal replacement affect the respiratory [ventilation (V̇e), tidal volume, and respiratory frequency], metabolic (V̇o2), and thermoregulatory (body temperature) responses to hypercapnia (7% CO2) in female Wistar rats. The parameters were measured in rats during different phases of the estrous cycle, and also in ovariectomized (OVX) rats supplemented with 17β-estradiol (OVX+E2), with a combination of E2 and progesterone (OVX+E2P), or with corn oil (OVX+O, vehicle). All experiments were conducted on day 8 after ovariectomy. The intact animals did not present alterations during normocapnia or under hypercapnia in V̇e, tidal volume, respiratory frequency, V̇o2, and V̇e/V̇o2 in the different phases of the estrous cycle. However, body temperature was higher in female rats on estrus. Hormonal replacement did not change the ventilatory, thermoregulatory, or metabolic parameters during hypercapnia, compared with the OVX animals. Nevertheless, OVX+E2, OVX+E2P, and OVX+O presented lower hypercapnic ventilatory responses compared with intact females on the day of estrus. Also, rats in estrus showed higher V̇e and V̇e/V̇o2 during hypercapnia than OVX animals. The data suggest that other gonadal factors, besides E2 and P, are possibly involved in these responses.

Takotsubo cardiomyopathy, a new concept of cardiomyopathy: clinical features and pathophysiology

Takotsubo cardiomyopathy, a new concept of cardiomyopathy, is characterized by transient cardiac dysfunction, commonly triggered by physical or emotional stress. Differential diagnosis is important, since takotsubo cardiomyopathy presents similar images to those shown in acute coronary syndrome, with ST-segment elevation, T-wave inversion, QT-prolongation, and others on electrocardiogram. Typically, apical involvement with hypercontraction of basal left ventricle (apical type) is predominant, but atypical types involving basal, mid-ventricular, and right ventricular myocardium are also described. In-hospital death occurs at similar level with patients with acute coronary syndrome, but it is significantly affected by underlying diseases. This disease presents diverse cardiac complications in acute phase, such as life-threatening ventricular arrhythmias, pump failure, cardiac rupture, and systemic embolism. The pathogenic mechanism of this disease is still unclear but sympathetic hyperactivity, as well as coronary vasospasm, microcirculatory disorder, and estrogen deficiency, have been considered as one of the most likely pathogenic mechanism. Long-term prognosis is also largely unknown. Issues such as establishment of acute phase treatment, prediction of cardiac complications, and prophylactic measures against recurrence need to be further explored.

Transdermal hormonal therapy in perimenstrual migraine: why, when and how?

Experimental and clinical evidence is strongly in favor of a role for estrogens in migraine. It is clear that estrogen fluctuations represent trigger factors for the attacks, while the resolution of these fluctuations (menopause) may be associated to the remission or, conversely, to the worsening of the disease. However, the exact mechanisms and mediators underlying the effects of estrogens in migraine are largely unknown. The exact mechanisms and mediators underlying the effects of estrogens in migraine are largely unknown. In this review, we summarize clinical and preclinical data that are relevant for the role of estrogens in migraine and we discuss how estrogen modulation can be exploited positively to improve hormonal-related migraine.

Transitory activation of the central and ovarian norepinephrine systems during cold stress-induced polycystic ovary in rats

Cold stress-induced ovarian sympathetic activation is associated with the development of ovarian cysts in rats. Although we have hypothesised that polycystic ovary (PCO) features induced by cold stress, as prevented by lesion of the noradrenergic nucleus locus coeruleus (LC), were a result of the increased activity of the ovarian norepinephrine (NE) system, this was not evident after 8 weeks of stress. In the present study, we investigated the temporal changes in LC and ovarian NE activities and steroid secretion in rats exposed to single (SS) or repeated (RS) cold stress. SS and 4 week (4W)-RS but not 8 week (8W)-RS increased c-Fos expression in the LC and ovarian NE release. Plasma oestradiol, testosterone and progesterone levels tended to increase in 4W-RS and were elevated in 8W-RS rats, which displayed PCO morphology. β-adrenergic receptor agonist increased steroid hormone release from the ovary of unstressed (US) but not from 8W-RS rats. To determine whether increased activity of noradrenergic system during the initial 4 weeks of RS would be sufficient to promote PCO, rats were exposed to 4 weeks of cold stress and kept in ambient temperature for the next 4 weeks (4W-RS/4W-US). Accordingly, PCO morphology, increased steroid secretion and decreased ovulation rate were found in 4W-RS/4W-US rats, strengthening the hypothesis that the initial increase in NE release triggers the development of PCO. The correlated activity of LC neurones and ovarian noradrenergic terminals and the induction of PCO in 4W-RS/4W-US rats provide functional evidence for a major role of NE in disrupting follicular development and causing the long-lasting endocrine abnormalities found in stress-induced PCO.

Cardiac and vascular gene profiles in an animal model of takotsubo cardiomyopathy

We investigated cardiac and vascular gene profiles in response to immobilization stress (IMO) in rats, an animal model of emotional stress-induced takotsubo cardiomyopathy using microarray analysis, followed by re-confirmation with real-time reverse transcription-polymerase chain reaction. Expression levels of the identified genes were further estimated by pretreatment with an α1-adrenoceptor blocker and/or a β1-adrenoceptor blocker. In response to IMO, expression of 46 genes was significantly altered in the heart and that of 49 genes was significantly altered in the aorta. Pathway analysis with DAVID Bioinformatics Resources indicated that regulation of transcription and response to endogenous stimulation were the top two scoring pathways. Altered expression of cardiac genes was blunted by pretreatment with a β1-adrenoceptor blocker or α1 + β1-adrenoceptor blockers. In contrast, that of aortic genes was blunted by pretreatment with an α1-adrenoceptor blocker or α1 + β1-adrenoceptor blockers. Activation of α1-adrenoceptor in the blood vessels or activation of β1-adrenoceptors in the heart were mainly responsible for emotional stress-induced alteration of cardiac and vascular gene profiles.

[Limbic system and autonomic nervous system]

The viral transneuronal labeling method using pseudorabies virus (PRV) is an ideal technique for identifying the central sites that regulate the sympathetic nervous system. Regions were identified in limbic system such as extended amygdaloid complex, lateral septum, infralimbic, insular, ventromedial temporal cortical regions, as well as in several hypothalamic and brain stem nuclei. Emotional stress causes rapid and transient expression of immediate early genes (IEGs) such as c-Fos in the brain, and the monitoring of IEGs has enabled the visualization of the neurocircuitry of stress. By a comparison of the data from the separate PRV and c-Fos neuroanatomical labeling techniques, the central sites which regulate emotional stress-induced sympathoadrenal activation can be deduced. Estrogen receptors are expressed in the brain, where estrogen modulates central nervous function and autonomic nervous function. Estrogen attenuated the stress-induced c-Fos expression in medial amygdaloid nucleus, paraventricular hypothalamic nucleus; these same regions contain central sympathetic neurons and neurons with immunoreactive estrogen receptors.

Cyclooxygenase and nitric oxide synthase in the presympathetic neurons in the paraventricular hypothalamic nucleus are involved in restraint stress-induced sympathetic activation in rats

Stress is one of the important factors to activate the sympathetic nervous system. We recently reported that central administration of corticotropin-releasing factor (CRF), known as a stress-related neuropeptide, increases the expression of both cyclooxygenase (COX) and nitric oxide synthase (NOS) in presympathetic neurons in the paraventricular hypothalamic nucleus (PVN). In the present study, therefore, we investigated whether brain COX and NOS can also mediate restraint stress (RS)-induced sympathetic activation by assessing the plasma catecholamine levels and neuronal activation of presympathetic neurons in the PVN. In addition, we examined effects of RS on the expression of both COX and NOS isozymes in the presympathetic PVN neurons. Intraperitoneal administration of an inhibitor for COX-1, COX-2 or inducible NOS (iNOS), but not for neuronal NOS (nNOS), reduced RS-induced elevation of plasma catecholamine levels and Fos expression in the presympathetic PVN neurons. Moreover, RS increased the expression of COX-1, COX-2 and iNOS in the presympathetic PVN neurons, whereas nNOS expression did not change. These results suggest that COX-1, COX-2 and iNOS in the presympathetic PVN neurons mediate acute RS-induced sympathetic activation.

A case of Takotsubo cardiomyopathy complicated by ventricular septal perforation

The patient was a 73-year-old female who developed chest pain and dyspnea 16 days after her husband passed away. ST segment elevation was detected on V2-5 by electrocardiography and emergency coronary arteriography was done for suspected acute myocardial infarction. No coronary arterial stenosis was present and ventricular septal perforation and takotsubo cardiomyopathy were diagnosed by left ventriculography. The perforation was closed and the patient was discharged 23 days after surgery. This patient had a very rare case of takotsubo cardiomyopathy, which was complicated by ventricular septal perforation and was saved by surgical treatment.

Effects of estrogen receptor alpha and beta gene deletion on estrogenic induction of progesterone receptors in the locus coeruleus in female mice

Locus coeruleus (LC) is involved in the LHRH regulation by gonadal steroids. We investigated the expression of progesterone and estrogen receptors (PR; ER) in LC neurons of ERalpha (alphaERKO) or ERbeta (betaERKO) knockout mice, and their wild-type (alphaWT and betaWT). Immunocytochemical studies showed that LC expresses PR and both ERs, although ERbeta was more abundant. Estradiol benzoate (EB) decreased ERalpha-positive cells in WT and betaERKO mice, and progesterone caused a further reduction, whereas none of the steroids influenced ERbeta expression. ERbeta deletion increased ERalpha while ERalpha deletion did not alter ERbeta expression. In both WT mice, EB increased PR expression, which was diminished by progesterone. These steroid effects were also observed in alphaERKO animals but to a lesser extent, suggesting that ERalpha is partially responsible for the estrogenic induction of PR in LC. Steroid effects on PR in betaERKO mice were similar to those in the alphaERKO but to a lesser extent, probably because PR expression was already high in the oil-treated group. This expression seems to be specific of LC neurons, since it was not observed in other areas studied, the preoptic area and ventromedial nucleus of hypothalamus. These findings show that LC in mice expresses alphaER, betaER, and PR, and that a balance between them may be critical for the physiological control of reproductive function.

Ovarian-steroid modulation of locus coeruleus activity in female rats: involvement in luteinising hormone regulation

The noradrenergic nucleus locus coeruleus (LC) has been reported to regulate luteinising hormone (LH) secretion in female rats. Both oestrogen and progestin receptors have been demonstrated in LC neurones, suggesting that these cells are possibly responsive to variations in circulating levels of ovarian steroids. We therefore evaluated changes in the activity of LC neurones during the oestrous cycle and after ovarian-steroid treatment in ovariectomised (OVX) rats, as determined by immunoreactivity to Fos-related antigens (FRA), which comprises all of the known members of the Fos family. Effects of ovarian steroids on the firing rate of LC neurones were also determined in a slice preparation. The number of FRA/tyrosine hydroxylase (TH)-immunoreactive (ir) neurones in the LC increased from 14.00-16.00 h on pro-oestrus, coinciding with the onset of the LH surge and rise in plasma progesterone. FRA immunoreactivity was unaltered during dioestrus. Oestradiol-treated OVX rats (OVX+E) displayed marked reduction in FRA/TH-ir neurones in LC compared to oil-treated OVX rats. Accordingly, oestradiol superfusion significantly reduced the spontaneous firing rate of LC neurones in slices from OVX rats. Compared to OVX+E, oestradiol-treated rats injected with progesterone at 08.00 h (OVX+EP) exhibited higher number of FRA/TH-ir neurones in the LC at 10.00 h and 16.00 h, and great amplification of the LH surge. Bath application of progesterone significantly increased the spontaneous firing rate of OVX+E LC neurones. Our data suggest that ovarian steroids may physiologically modulate the activity of LC neurones in females, with possible implications for LH secretion. Moreover, oestradiol and progesterone appear to exert opposite and complementary effects (i.e. whereas oestradiol inhibits, progesterone, after oestradiol priming, stimulates LC activity).

Oestrogen receptors in the central nervous system and evidence for their role in the control of cardiovascular function

Oestrogen is considered beneficial to cardiovascular health through protective effects not only on the heart and vasculature, but also on the autonomic nervous system via actions on oestrogen receptors. A plethora of evidence supports a role for the hormone within the central nervous system in modulating the pathways regulating cardiovascular function. A complex interaction of several brainstem, spinal and forebrain nuclei is required to receive, integrate and co-ordinate inputs that contribute appropriate autonomic reflex responses to changes in blood pressure and other cardiovascular parameters. Central effects of oestrogen and oestrogen receptors have already been demonstrated in many of these areas. In addition to the classical nuclear oestrogen receptors (ERalpha and ERbeta) a recently discovered G-protein coupled receptor, GPR30, has been shown to be a novel mediator of oestrogenic action. Many anatomical and molecular studies have described a considerable overlap in the regional expression of these receptors; however, the receptors do exhibit specific characteristics and subtype specific expression is found in many autonomic brain areas, for example ERbeta appears to predominate in the hypothalamic paraventricular nucleus, whilst ERalpha is important in the nucleus of the solitary tract. This review provides an overview of the available information on the localisation of oestrogen receptor subtypes and their multitude of possible modulatory actions in different groups of neurochemically and functionally defined neurones in autonomic-related areas of the brain.

Sex differences in psychopathology: of gonads, adrenals and mental illness

Stress-related disorders such as anxiety and depression are disproportionately prevalent in women. Women are more likely to experience depression and anxiety disorders during periods of marked hormonal fluctuations, suggesting that gonadal hormones are involved in stress pathology. Depression and anxiety are both associated with aberrant secretion of glucocorticoids, which also show marked fluctuations across the reproductive cycle and in response to gonadal steroids. Thus, interactions between gonadal and stress hormones may play a major role in predisposing females to stress-related disease. The purpose of this brief review is to highlight preclinical data regarding the role of estrogens in depression and anxiety-like behaviors. While it is evident the exogenous estrogens modulate affective behavior in rodents, there is some disagreement in the literature, perhaps related to experimental designs that vary with respect to administration parameters and stress. Beneficial effects of estrogens on mood are most likely due to estrogen receptor (ER)beta signaling. The antidepressant and anxiolytic effects of ERbeta are consistent with its role in attenuating glucocorticoid responses to stress, suggesting that estrogens, acting at ERbeta, may improve mood by suppressing glucocorticoid hyperactivity. However, additional studies demonstrate that ERbeta signaling in the hippocampus is sufficient to induce antidepressant and anxiolytic behaviors. Thus, ERbeta may improve mood via primary actions on hypothalamic (i.e., paraventricular nucleus) and/or extra-hypothalamic sites. Overall, the preclinical research suggests that selective ER modulators targeting ERbeta may be an attractive alternative or adjunct treatment to currently prescribed antidepressants or anxiolytics.

Cardiac sympathetic neuroimaging: summary of the First International Symposium

The First International Symposium on Cardiac Sympathetic Neuroimaging brought together for the first time clinical and preclinical researchers evaluating autonomic and neurocardiologic disorders by this modality. The invited lectures and posters presented some uses of cardiac sympathetic neuroimaging for diagnosis, prognosis, and monitoring treatments. The Symposium also included a discussion about whether and how to expand the availability of cardiac sympathetic neuroimaging at medical centers in the United States. Here, we review the background for the Symposium, provide an annotated summary of the lectures and posters, discuss some of the take-home points from the roundtable discussion, and propose a plan of action for the future.

Catecholamines and estrogen are involved in the pathogenesis of emotional stress-induced acute heart attack

Emotional stress triggers takotsubo cardiomyopathy in postmenopausal women. Clinical analysis of autonomic nervous function has revealed a transient increase of sympathetic nervous activity and decrease of vagal nervous activity. Immobilization (IMO) stress of rats can reproduce the electrocardiographic and left ventriculographic changes that occur in takotsubo cardiomyopathy, both of which are prevented by combined blockade of alpha- and beta-adrenoceptors. Estrogen supplementation partially attenuated these cardiac changes. It also attenuated the IMO-induced increase of c-Fos immunoreactivity, or c-fos mRNA expression in the lateral septum, medial amygdaloid nucleus, paraventricular hypothalamic nucleus, dorsomedial hypothalamic nucleus, laterodorsal tegmental nucleus, and locus ceruleus; these regions contain central sympathetic neurons and neurons with immunoreactive estrogen receptors. It also downregulated c-fos mRNA expression in the adrenal gland and the heart, suggesting an increase of estrogen attenuated the stress-induced hypothalamo-sympathoadrenal outflow from the central nervous system to the target organs. Estrogen treatment also upregulated the levels of cardioprotective substances, such as atrial natriuretic peptide and heat shock protein 70, in the heart. These data suggest that reduction of estrogen levels following menopause might be involved in the primary cause of takotsubo cardiomyopathy both by indirect action on the nervous system and by direct action on the heart.

Effects of estrogen on stress-induced activation of peptide neurons in PVN of ovariectomized rats

Estrogen has been implicated in brain function related to stress responses. We investigated whether estrogen affects psychological stress-induced activation of peptide-containing or nitric oxide-producing neurons in the paraventricular hypothalamic nucleus (PVN) in ovariectomized (OVX) rats, both placebo-treated (OVX + Pla) and estrogen-treated (OVX + E2) by comparison of c-Fos expression using immunohistochemistry. Cage-switch stress increased activation in oxytocinergic neurons in the parvocellular PVN (pPVN) in OVX + Pla, but not in that of OVX + E2, rats. Moreover, the stress-induced activation in NADPH-diaphorase-positive neurons in the pPVN was larger in the OVX + E2 than in the OVX + Pla group. These findings suggest that estrogen attenuates the activation of oxytocinergic neurons in the pPVN, at least in part via nitric oxide.

Estradiol replacement enhances sleep deprivation-induced c-Fos immunoreactivity in forebrain arousal regions of ovariectomized rats

To understand how female sex hormones influence homeostatic mechanisms of sleep, we studied the effects of estradiol (E2) replacement on c-Fos immunoreactivity in sleep/wake-regulatory brain areas after sleep deprivation (SD) in ovariectomized rats. Adult rats were ovariectomized and implanted subcutaneously with capsules containing 17β-E2(10.5 μg; to mimic diestrous E2levels) or oil. After 2 wk, animals with E2capsules received a single subcutaneous injection of 17β-E2(10 μg/kg; to achieve proestrous E2levels) or oil; control animals with oil capsules received an oil injection. Twenty-four hours later, animals were either left undisturbed or sleep deprived by “gentle handling” for 6 h during the early light phase, and killed. E2treatment increased serum E2levels and uterus weights dose dependently, while attenuating body weight gain. Regardless of hormonal conditions, SD increased c-Fos immunoreactivity in all four arousal-promoting areas and four limbic and neuroendocrine nuclei studied, whereas it decreased c-Fos labeling in the sleep-promoting ventrolateral preoptic nucleus (VLPO). Low and high E2treatments enhanced the SD-induced c-Fos immunoreactivity in the laterodorsal subnucleus of the bed nucleus of stria terminalis and the tuberomammillary nucleus, and in orexin-containing hypothalamic neurons, with no effect on the basal forebrain and locus coeruleus. The high E2treatment decreased c-Fos labeling in the VLPO under nondeprived conditions. These results indicate that E2replacement modulates SD-induced or spontaneous c-Fos expression in sleep/wake-regulatory and limbic forebrain nuclei. These modulatory effects of E2replacement on neuronal activity may be, in part, responsible for E2's influence on sleep/wake behavior.

Activation of ERbeta increases levels of phosphorylated nNOS and NO production through a Src/PI3K/Akt-dependent pathway in hypothalamic neurons

Estrogen plays a role in restoring homeostatic balance during the stress response by altering hypothalamic function and NO production in the brain. While we know that estrogen acts on the hypothalamus to stimulate the NO system through an ERbeta-dependent mechanism in neurons, the molecular mechanisms responsible for these effects are unknown. Because phosphorylation of nNOS at Ser(1412) increases nNOS activity which leads to increased NO production, we investigated the effects of ERbeta activation on nNOS phosphorylation at Ser(1412) and NO production in primary hypothalamic neurons. Using the selective ERbeta agonist, DPN (10nM), we show that activation of ERbeta rapidly increases phosphorylation levels of nNOS at Ser(1412) and NO production. We also show that the PI3K pathway, but not the MAPK pathway, mediates the increases in levels of Ser(1412) phosphorylation and NO production induced by ERbeta activation, as the selective PI3K inhibitor, LY294002 (10microM), blocked the effects of ERbeta activation. Finally, we demonstrate that Src kinase acts upstream of the PI3K/Akt pathway based on our finding that the selective Src inhibitor, PP2 (10microM), blocked the increases in nNOS phosphorylation levels, NO production, and PI3K/Akt activity induced by ERbeta activation. Together, our results show that Src kinase mediates ERbeta-induced increases in phosphorylation levels of nNOS at Ser(1412) and NO production by activating the PI3K/Akt pathway. These findings provide novel insight into the signaling mechanisms through which E2 stimulates the NO system in hypothalamic neurons.

Chronic intracerebral prolactin attenuates neuronal stress circuitries in virgin rats

Prolactin (PRL) has been shown to promote maternal behaviour, and to regulate neuroendocrine and emotional stress responses. These effects appear more important in the peripartum period, when the brain PRL system is highly activated. Here, we studied the mechanisms that underlie the anti-stress effects of PRL. Ovariectomized, estradiol-substituted Wistar rats were implanted with an intracerebroventricular cannula and treated with ovine PRL (0.01, 0.1 or 1 microg/h; 5 days via osmotic minipumps) or vehicle, and their responses to acute restraint stress was assessed. Chronic PRL treatment exerted an anxiolytic effect on the elevated plus-maze, and attenuated the acute restraint-induced rise in plasma adrenocorticotropin, corticosterone and noradrenaline. At the neuronal level, in situ hybridization revealed PRL effects on the expression patterns of the immediate-early gene c-fos and corticotropin-releasing factor (CRF). Under basal conditions, PRL significantly reduced c-fos mRNA expression within the central amygdala. In response to restraint, the expression of both c-fos mRNA and protein and of CRF mRNA was decreased in the parvocellular part of the paraventricular nucleus (PVN) of PRL-treated compared with vehicle-treated animals. In conclusion, our data demonstrate that chronic elevation of PRL levels within the brain results in reduced neuronal activation within the hypothalamus, specifically within the PVN, in response to an acute stressor. Thus, PRL acting at various relevant brain regions exerts profound anxiolytic and anti-stress effects, and is likely to contribute to the attenuated stress responsiveness found in the peripartum period, when brain PRL levels are physiologically upregulated.

Potential role of female sex hormones in the pathophysiology of migraine

Clinical evidence indicates that female sex steroids may contribute to the high prevalence of migraine in women, as well as changes in the frequency or severity of migraine attacks that are in tandem with various reproductive milestones in women's life. While female sex steroids do not seem to be involved in the pathogenesis of migraine per se, they may modulate several mediators and/or receptor systems via both genomic and non-genomic mechanisms; these actions may be perpetuated at the central nervous system, as well as at the peripheral (neuro)vascular level. For example, female sex steroids have been shown to enhance: (i) neuronal excitability by elevating Ca(2+) and decreasing Mg(2+) concentrations, an action that may occur with other mechanisms triggering migraine; (ii) the synthesis and release of nitric oxide (NO) and neuropeptides, such as calcitonin gene-related peptide CGRP, a mechanism that reinforces vasodilatation and activates trigeminal sensory afferents with a subsequent stimulation of pain centres; and (iii) the function of receptors mediating vasodilatation, while the responses of receptors inducing vasoconstriction are attenuated. The serotonergic, adrenergic and gamma-aminobutyric acid (GABA)-ergic systems are also modulated by sex steroids, albeit to a varying degree and with potentially contrasting effects on migraine outcome. Taken together, female sex steroids seem to be involved in an array of components implicated in migraine pathogenesis. Future studies will further delineate the extent and the clinical relevance of each of these mechanisms, and will thus expand the knowledge on the femininity of migraine.

Chronic Estrogen Supplementation Following Ovariectomy Improves the Emotional Stress-Induced Cardiovascular Responses by Indirect Action on the Nervous System and by Direct Action on the Heart

BACKGROUND

Takotsubo cardiomyopathy is triggered by emotional or physical stress especially in post-menopausal women. A reduction in estrogen levels following menopause might underlie the high incidence of takotsubo cardiomyopathy.

METHODS AND RESULTS

The left ventricular contraction between ovariectomized rats (OVX) and OVX with estrogen supplementation (OVX + E) while subjected to immobilization stress (IMO) was compared. The IMO in combination with general anesthesia impaired the left ventricular contraction in both OVX and OVX + E. Estrogen supplementation tended to improve the IMO-induced cardiac dysfunction and significantly attenuated the increase of blood pressure and heart rate. To understand the protective mechanism of estrogen, the expression of c-fos mRNA, a marker of cellular activation was compared. The mRNA expression of cardioprotective substances in the heart was also investigated. In the OVX + E, the levels of c-fos mRNA were significantly decreased in the paraventricular hypothalamic nucleus, adrenal gland and left ventricle, suggesting that an increase of estrogen attenuates the emotional stress-induced hypothalamo-sympatho-adrenal outflow from the central nervous system to the target organs. An expression of heat shock protein 70 and atrial natriuretic peptide was significantly augmented in the OVX + E.

CONCLUSIONS

These data suggest that estrogen supplementation partially prevents emotional stress-induced cardiovascular responses both by indirect action on the nervous system and by direct action on the heart.

Estrogen in the paraventricular nucleus attenuates L-glutamate-induced increases in mean arterial pressure through estrogen receptor beta and NO

Estrogen (E2) acts in the brain to decrease blood pressure (BP) responses to psychological stress. A likely site for the effects of E2 is the hypothalamic paraventricular nucleus (PVN), an important regulator of autonomic functions. We studied the effects of E2 in the PVN on BP and heart rate (HR) responses to l-glutamate injections into the PVN of male urethane-anesthetized rats. Microinjections of l-glutamate (50 nmol) into the PVN increased BP by 14+/-2.5 mm Hg and HR by 30+/-5.6 bpm. Microinjections of E2 (0.1, 1, and 10 pmol) into the PVN 30 minutes before l-glutamate dose-dependently attenuated the pressor response by 25%, 34%, and 59%, respectively, but did not affect HR. We determined that E2 receptor (ER) beta mediates the effect of E2, because activation of ERbeta with diarylpropionitrile (50 pmol) attenuated the response by 57%, whereas activation of ERalpha with propyl-pyrazole-triol (20 pmol) had no effect. Furthermore, inhibition of ERbeta with R,R-tetrahydrochrysene (50 pmol) blocked the effect of E2, but inhibition of ERalpha with methyl-piperidino-pyrazole (1 nmol) did not. Finally, we found that the effect of E2 is mediated by NO, because the NO synthase (NOS) inhibitor, N(G)-nitro-l-arginine methyl ester (2 nmol), the neuronal NOS inhibitor, 7-nitroindazole sodium salt (0.1 pmol), and the endothelial NOS inhibitor, N5-(1-iminoethyl)-l-ornithine (200 pmol) blocked the effect of E2. The effect was partially blocked with the gamma-aminobutyric acid(A) receptor inhibitor bicuculline. Our results demonstrate that E2 in the PVN attenuates the l-glutamate-induced pressor response and that this effect is mediated by ERbeta, NO produced by neuronal NO synthase and eNOS, and partly by gamma-aminobutyric acid.

Effects of short- and long-term estrogen and progesterone replacement on behavioral responses and c-fos mRNA levels in female rats after acute cocaine administration

It is well established that there are estrous cycle differences in cocaine-induced behavioral activity, implicating fluctuations in levels of estrogen and progesterone throughout the cycle in these alterations in behavior. However, the mechanisms by which steroids alter cocaine-induced behavioral responses have yet to be determined. The aim of this study was to determine whether short- or long-term estrogen and progesterone administration differentially alters behavioral responses to cocaine. Estrogen (50 microg) was administered 30 min or 48 h before cocaine (15 mg/kg, i.p.) administration; progesterone (500 microg) was administered 30 min or 24 h before cocaine. Short-term estrogen replacement decreased cocaine-induced ambulations. Short-term progesterone decreased rearing, whereas long-term progesterone decreased ambulations. Although cocaine increased levels of c-fos mRNA, none of the estrogen or progesterone replacement paradigms affected this measure. Because long-term estrogen replacement has been shown to have no effect on locomotor activity after acute cocaine administration, our observations suggest that short-term estrogen may underlie behavioral alterations. These findings suggest that after acute cocaine administration, while estrogen may activate only membrane receptors to alter behavioral responses to cocaine, progesterone activates both nuclear and membrane receptors.