IMPLICATION OF CENTRAL NEUROHYPOPHYSEAL HORMONE RECEPTOR-MEDIATED ACTION IN THE TIMING OF REPRODUCTIVE EVENTS - EVIDENCE FROM NOVEL OBSERVATIONS ON THE EFFECT OF A VASOTOCIN ANALOG ON SINGING BEHAVIOR OF THE CANARY

A highly discrete distribution of neurohypophyseal hormone receptors w as discovered in the mammalian and avian brain. These receptors are he terogeneous. In rat brain oxytocin (OT) and V1a receptors can be disti nguished which bind OT with an order of magnitude difference in affini ty and which are located in discrete sites of the limbic-midbrain circ uitry. In the brain of the canary low and high affinity vasotocin (VT) sites were identified; the latter putative VT receptors were found ex clusively localized in the area encapsulating the nucleus robustus arc histriatalis (RA). We show with recordings of singing behaviour that a VT analogue promotes the chain of seasonal events in this behaviour.