Immunocytochemical demonstration of vasopressin and oxytocin in the rat brain by light and electron microscopy.

Vasopressin and oxytocin were demonstrated by means of the unlabeled antibody enzyme method in the rat central nervous system. Vasopressin and oxytocin fibers of the magnocellular nuclei were found to run towards the amygdala, hippocampus, and spinal cord. From the parvocellular suprachiasmatic nucleus only vasopressin containing fibers were found to run towards the organum vasculosum lamina terminalis, lateral septum, and lateral habenular nucleus. Immunoelectron microscopy, using the preembedding staining technique, frequently demonstrated vasopressin-containing synapses on neuronal structures in the lateral septum, lateral habenular nucleus, and amygdala. These results suggest a putative neurotransmitter role for these neuropeptides.