Extrahypothalamic vasopressin and oxytocin in the human brain; presence of vasopressin cells in the bed nucleus of the stria terminalis.

In the present study, the distribution of extrahypothalamic vasopressin (VP) and oxytocin (OXT) in the human brain was investigated by means of immunocytochemistry. In the septum verum, few VP fibers were found in the nucleus septalis lateralis and medialis (NSL and NSM), and in the bed nucleus of the anterior commissure. Very few VP and OXT fibers were present in the amygdala and in the hippocampus, mainly around the rostral tip of the lateral ventricle on the level of the pes hippocampi. The locus coeruleus (LC) contained dense networks of VP fibers and, although to a lesser extent, OXT fibers over its entire rostrocaudal extension. VP-immunoreactive neurons were present in the bed nucleus of the stria terminalis in a number of subjects, while no OXT cells were found in this structure. Thus, the VP innervation of limbic structures in the human brain, in particular of the NSL, was found to be clearly less pronounced than in the rat brain. The VP innervation of the LC, by contrast, was denser in the human brain than in the rat brain. No sex differences were found in the VP innervation of the human brain. These findings stress the need for caution in extrapolation of data concerning peptidergic innervation of the rat brain towards the human brain.