Effects of estrogen on stress responses in women

Psychoticism and neuroticism predict cocaine dependence and future cocaine use via different mechanisms

BACKGROUND

Personality characteristics have been associated with cocaine use. However, little is known about the mechanisms through which personality could impact drug use. The present study investigated the cross-sectional and prospective relationships between personality dimensions (i.e., impulsivity, neuroticism) and problematic cocaine use. Reactivity to a pharmacological stressor as a potential mediator of the relationship between neuroticism and future cocaine use was also examined.

METHODS

Participants were 53 cocaine-dependent individuals and 47 non-dependent controls. Subjects completed the Eysenck Personality Questionnaire (EPQ) at baseline and were administered i.v. corticotrophin releasing hormone (CRH; 1 μg/kg). Cocaine use in the 30 days following CRH administration was measured.

RESULTS

Cocaine-dependent individuals had higher scores on the psychoticism (i.e., impulsivity, aggression; p=0.02) and neuroticism (p<0.01) scales of the EPQ than non-dependent controls. Cocaine-dependent individuals also had a greater subjective stress response to CRH than controls (p<0.01). Cocaine-dependent individuals with elevated psychoticism used significantly more cocaine over the follow-up period (p<0.05), whereas individuals with elevated neuroticism trended towards using cocaine more frequently over the follow-up (p=0.07). Finally, there was a trend for an indirect effect of neuroticism on frequency of cocaine use through subjective reactivity to CRH.

CONCLUSIONS

The findings extend past research on the association between personality and cocaine use, and suggest that motives for cocaine use may systematically vary across personality characteristics. Moreover, tailoring therapeutic interventions to individuals' personalities may be an area that warrants further investigation.

Gender differences in the effect of early life trauma on hypothalamic-pituitary-adrenal axis functioning

BACKGROUND

The objective of this study was to examine the modifying effect of gender on the association between early life trauma and the hypothalamic-pituitary-adrenal (HPA) axis response to a pharmacologic challenge and a social stress task in men and women. Participants (16 men, 23 women) were the control sample of a larger study examining HPA axis function. Individuals with major depressive disorder, posttraumatic stress disorder, bipolar disorder, or psychotic or eating disorders were excluded.

METHODS

In two test sessions, subjects received 1 µg/kg of corticotropin-releasing hormone (CRH) intravenously and participated in the Trier Social Stress Test (TSST). Primary outcomes included plasma cortisol and corticotropin levels measured at baseline and more than five time points following the challenges. Predictors included gender and early life trauma, as measured by the Early Trauma Index. Using factor analysis, the domains general trauma, severe trauma, and the effects of trauma were established. Using regression, these constructs were used to predict differential HPA reactivity in men and women following the challenges.

RESULTS

The three factors accounted for the majority of the variance in the ETI. Following the CRH challenge, women had higher overall corticotropin response as dictated by the area under the curve analysis. There were no significant associations between trauma and neuroendocrine response to the TSST.

CONCLUSIONS

CRH challenge results indicate that gender differences in the impact of early trauma may help explain the differential gender susceptibility to psychopathology following adverse childhood events. This may help explain gender differences in some stress-sensitive psychiatric disorders.

Tibolone rapidly attenuates the GABAB response in hypothalamic neurones

Tibolone is primarily used for the treatment of climacteric symptoms. Tibolone is rapidly converted into three major metabolites: 3 alpha- and 3beta-hydroxy (OH)-tibolone, which have oestrogenic effects, and the Delta 4-isomer (Delta 4-tibolone), which has progestogenic and androgenic effects. Because tibolone is effective in treating climacteric symptoms, the effects on the brain may be explained by the oestrogenic activity of tibolone. Using whole-cell patch clamp recording, we found previously that 17beta-oestradiol (E(2)) rapidly altered gamma-aminobutyric acid (GABA) neurotransmission in hypothalamic neurones through a membrane oestrogen receptor (mER). E(2) reduced the potency of the GABA(B) receptor agonist baclofen to activate G-protein-coupled, inwardly rectifying K(+) (GIRK) channels in hypothalamic neurones. Therefore, we hypothesised that tibolone may have some rapid effects through the mER and sought to elucidate the signalling pathway of tibolone's action using selective inhibitors and whole cell recording in ovariectomised female guinea pigs and mice. A sub-population of neurones was identified post hoc as pro-opiomelanocortin (POMC) neurones by immunocytochemical staining. Similar to E(2), we have found that tibolone and its active metabolite 3 beta OH-tibolone rapidly reduced the potency of the GABA(B) receptor agonist baclofen to activate GIRK channels in POMC neurones. The effects were blocked by the ER antagonist ICI 182 780. Other metabolites of tibolone (3 alpha OH-tibolone and Delta 4-tibolone) had no effect. Furthermore, tibolone (and 3 beta OH-tibolone) was fully efficacious in ER alpha knockout (KO) and ER beta KO mice to attenuate GABA(B) responses. The effects of tibolone were blocked by phospholipase C inhibitor U73122. However, in contrast to E(2), the effects of tibolone were not blocked by protein kinase C inhibitors or protein kinase A inhibitors. It appears that tibolone (and 3 beta OH-tibolone) activates phospholipase C leading to phosphatidylinositol bisphosphate metabolism and direct alteration of GIRK channel function. Therefore, tibolone may enhance synaptic efficacy through the G(q) signalling pathways of mER in brain circuits that are critical for maintaining homeostatic functions.

Modulation of hypothalamic neuronal activity through a novel G-protein-coupled estrogen membrane receptor

Estrogens are involved in the hypothalamic control of multiple homeostatic functions including reproduction, stress responses, energy metabolism, sleep cycles, temperature regulation and motivated behaviors. The actions of 17beta-estradiol (E(2)) in the brain have been attributed to the activation of estrogen receptors alpha and beta, as well as G-protein-coupled or other membrane-associated estrogen receptors. Recently, we have identified a putative membrane-associated estrogen receptor that is coupled to desensitization of GABA(B) receptors in guinea pig and mouse hypothalamic neurons including proopiomelanocortin (POMC) neurons. We have synthesized a new nonsteroidal compound, STX, which selectively targets the Galphaq-coupled phospholipase C-protein kinase C-protein kinase A pathway, and have established that STX is more potent than E(2) in mediating this desensitization in an ICI 182,780-sensitive manner in both guinea pig and mouse neurons. Both E(2) and STX are fully efficacious in estrogen receptor alpha, beta knock-out mice. Finally, we observed that the putative membrane-associated estrogen receptor is different from GPR30 in arcuate neurons using whole-cell patch recording in hypothalamic slices from GPR30 knock-out mice. Collectively, these findings suggest that the mER is distinct from ERalpha, ERbeta or GPR30.

Social support and resilience to stress across the life span: a neurobiologic framework

This review discusses selected neurobiologic and genetic factors-including noradrenergic and hypothalamic-pituitary-adrenal axis markers, oxytocin pathways, and serotonin transporter and brain-derived neurotrophic factor gene polymorphisms-in the context of resilience to stress, with an emphasis on social support. Social support's impact on medical and psychiatric health outcomes is reviewed, and putative mediators are discussed. The reviewed literature indicates that social support is exceptionally important to maintaining good physical and psychological health in the presence of genetic, developmental, and other environmental risks. Future studies should continue to explore the neurobiologic factors associated with social support's contribution to stress resilience.

A G-protein-coupled estrogen receptor is involved in hypothalamic control of energy homeostasis

Estrogens are involved in the hypothalamic control of multiple homeostatic functions including reproduction, stress responses, energy metabolism, sleep cycles, temperature regulation, and motivated behaviors. The critical role of 17beta-estradiol (E2) is evident in hypoestrogenic states (e.g., postmenopause) in which many of these functions go awry. The actions of E2 in the brain have been attributed to the activation of estrogen receptors alpha and beta through nuclear, cytoplasmic, or membrane actions. However, we have identified a putative membrane-associated estrogen receptor that is coupled to desensitization of GABAB and mu-opioid receptors in guinea pig and mouse hypothalamic proopiomelanocortin neurons. We have synthesized a new nonsteroidal compound, STX, which selectively targets the Galphaq-coupled phospholipase C-protein kinase C-protein kinase A pathway, and have established that STX is more potent than E2 in mediating this desensitization in an ICI 182, 780-sensitive manner in both guinea pig and mouse neurons. Both E2 and STX were fully efficacious in estrogen receptor alpha,beta knock-out mice. Moreover, in vivo treatment with STX, similar to E2, attenuated the weight gain in hypoestrogenic female guinea pigs. Therefore, this membrane-delimited signaling pathway plays a critical role in the control of energy homeostasis and may provide a novel therapeutic target for treatment of postmenopausal symptoms and eating disorders in females.