IMMUNOELECTRON MICROSCOPIC DEMONSTRATION OF OXYTOCIN AND VASOPRESSIN IN PITUICYTES AND IN NERVE-TERMINALS FORMING SYNAPTOID CONTACTS WITH PITUICYTES IN THE RAT NEURAL LOBE

A pre-embedding immunoelectron microscopic technique was used to obtain morphological evidence for a role of oxytocin and vasopressin in the regulation of their own or each others release from the neural lobe. No synaptoid contacts of oxytocin- or vasopressin-containing axons with other neuronal structures were observed. However, synaptoid contacts of oxytocin- and vasopressin-containing nerve terminals and Herring bodies with pituicytes were frequently observed. These findings suggest that the pituicyte may participate in auto- and/or cross-regulation of oxytocin and vasopressin release. Moreover, oxytocin and vasopressin precursor-derived peptides were found in the cytoplasm of some pituicytes, an unexpected finding that will be discussed.