Hypothalamic oxytocin

Immunocytochemical studies in normal rats show an association between oxytocin (OT) neurons and cerebral blood vessels. This is supported by the finding of neurophysin (NP) immunoreactivity in blood vessels and pia-arachnoid tissue of rats with hereditary vasopressin (VP) and VP-NP deficiency. OT and OT-NP fibers were visualized in pia-arachnoid and blood vessels at the base of the brain and, to a lesser extent, over the dorsal surface. OT constricts human basilar artery with a threshold response in the 10(-10) M range, and an ED50 of 4.8 X 10(-9) M. These observations suggest that extrahypothalamic projections of OT neurons may modulate cerebrovascular function.