Immunocytochemical Study on the Extrahypothalamic Projections of Oxytocinergic and Vasopressinergic Neurons in the Mouse

= Abstract = An immunocytochemical study on the pathways and distribution of extrahypothalamic projections of oxytocinergic and vasopressinergic neurons was performed. Monoclonal antibodies to oxytocin and vasopressin, avidin-blottn-peroxidase complex, vibratomy, and free floating methods were applied in the immunocytochemical procedure of the mouse brain. Oxytocinergic fibers arose from the paraventricular nucleus and bed nucleus of the stria terminalis and projected mainly to the brain stem. The fibers to the brain stem followed two major courses and reached the central gray area, lateral reticular nucleus, dorsal motor nucleus of vagus, locus coeruleus, etc. Other fibers projected to the various regions of the forebrain such as the amygdala, and the septal nuclei. Vasopressinergic fibers were present mainly in the amygdala, and a few fibers were observed in the lateral habenula and lateral reticular nucleus. In certain nuclei, the oxytocingergic and vasopressinergic fibers ramified and formed the perineuronal punctate structures. The extensive pathway in the central nervous system and synaptic-like localization of oxytocinergic and vasopressinergic fibers revealed in this study support their role as neuromodulators or neurotransmitters and a wide variety of their functions in the behavioral process, memory, and modulation of autonomic nervous system. In view of its localization, oxytocin is thought to playa dominant role in the regulation of the autonomic nervous system.