Enkephalin in the Rat Neural Lobe: Immunocytochemical Evidence for its Presence Within Synaptic Elements on Pituicytes

Abstract

Publisher Summary In the following years, the conclusion was drawn that the hypothalamo-neurohypophyseal system (HNS) contains vasopressin (VP), adiuretin, and oxytocin (OXT). Moreover, these hormones are accompanied by proteins called neurophysins, from which they could be liberated. Until the mid-seventies, nobody doubted the idea that VP and OXT are the hormones that are exclusively synthetized, transported, and released within the mammalian HNS. However, in the past few years, mainly due to the application of immunocytochemistry (ICC), the number of compounds reported to be present within the rat magnocellular PVN and SON increased tremendously. Most of these compounds have also been demonstrated in the neural lobe, which is logical, because it is one of the main projection sites of the SON. In addition, several of these compounds would coexist with VP or OXT. Unfortunately, most of these compounds have been demonstrated solely by ICC, which has its pitfalls. This chapter attempts to sum up and subsequently integrate the progress in biochemical, pharmacological and immunocytochemical research on opioid peptides in the neural lobe that has been achieved in the past few years.