Colocalization of estrogen β-receptor messenger RNA with orphanin FQ, vasopressin and oxytocin in the rat hypothalamic paraventricular and supraoptic nuclei

Abstract

The functional significance of the novel estrogen receptor β in brain areas that exclusively contain the ERβ receptor subtype such as the paraventricular (PVN) and the supraoptic (SON) nuclei of the hypothalamus is not yet fully understood. The present study attempts to characterize the peptidergic nature of the ERβ-containing neuronal population in the PVN and the SON using the double in situ histochemistry method in the female rat. Using this method, the ERβ mRNA coexpressions with the novel opioid neuropeptide (orphanin FQ and its receptor ORL1) mRNA in addition to the previously reported neuropeptide (arginine vasopressin-AVP, oxytocin-OXY, corticotropin releasing hormone-CRH, enkephalin-ENK) mRNAs were assessed. In the PVN, roughly half of the ERβ expression was colocalized with the prepro-orphanin FQ mRNA, which was comparable to the colocalization observed between the ERβ and AVP mRNAs in the same region. In addition, there was 20% overlap between the ERβ and ORL1 receptor mRNAs, and 10% overlap between the ERβ and OXY mRNAs in the PVN. By contrast, the coexpression between the prepro-orphanin FQ and ERβ mRNAs was less striking in the SON. Potential interactions between the ERβ and the well-characterized AVP-OXY neurosecretory system as well as the novel OFQ-ORL1 opioid neuropeptide system may provide new leads for the functional significance of ERβ, specifically in stress/autonomic responses.