Corticotrophin-releasing hormone, proenkephalin A and oxytocin mRNA's in the paraventricular nucleus during pregnancy and parturition in the rat.

Abstract

Since stress and opioids affect oxytocin secretion we investigated the involvement of corticotrophin-releasing hormone (CRH) and enkephalin on the regulation of oxytocin production during pregnancy and parturition by measuring CRH, proenkephalin A (PENK) and oxytocin mRNA's in the paraventricular nucleus (PVN) using quantitative in situ hybridisation. On day 21 of pregnancy and during parturition CRH mRNA content and the number of parvocellular neurones expressing CRH were significantly decreased but neither PENK nor oxytocin mRNA was altered. The suppression of the CRH gene in late pregnancy and parturition may lead to the previously reported reduction in stress responses during lactation.