EXTRA-NUCLEAR ESTROGEN RECEPTOR GPR30 REGULATES SEROTONIN FUNCTION IN RAT HYPOTHALAMUS

Selective serotonin reuptake inhibitors (SSRIs), such as Prozac (R), are used to treat mood disorders. SSRIs attenuate (i.e. desensitize) serotonin 1A (5-HT1A) receptor signaling, as demonstrated in rats through decreased release of oxytocin and adrenocorticotropin hormone (ACTH) following 5-HT1A receptor stimulation. Maximal therapeutic effects of SSRIs for treatment of mood disorders, as well as effects on hypothalamic 5-HT1A receptor signaling in animals, take 1 to 2 weeks to develop. Estradiol also attenuates 5-HT1A receptor signaling, but, in rats, these effects occur within 2 days; thus, estrogens or selective estrogen receptor modulators may serve as useful short-term tools to accelerate desensitization of 5-HT1A receptors in response to SSRIs if candidate estrogen receptor targets in the hypothalamus are Identified. We found high levels of GPR30, which has been identified recently as a pertussis-toxin (PTX) sensitive G-protein-coupled estrogen receptor, in the hypothalamic paraventricular nucleus (PVN) of rats, Double-label immunohistochemistry revealed that GPR30 co-localizes with 5-HT1A receptors, corticotrophin releasing factor (CRF) and oxytocin in neurons in the PVN. Pretreatment with PTX to the PVN before peripheral injections of 17-beta-estradiol 3-benzoate completely prevented the reduction of the oxytocin response to the 5-HT1A receptor agonist, (+)-8-hydroxy-2-dipropylaminotetralin (DPAT). Treatment with the selective GRP30 agonist, G-1, attenuated 5-HT1A receptor signaling in the PVN as measured by an attenuated oxytocin (by 29%) and ACTH (by 31%) response to DPAT. This study indicates that a putative extra-nuclear estrogen receptor, GPR30, may play a role In estradiol-mediated attenuation of 5-HT1A receptor signaling, and potentially in accelerating the effects of SSRIs in treatment of mood disorders. (C) 2009 IBRO. Published by Elsevier Ltd. All rights reserved.