Action of posterior pituitary neuropeptides on the nigrostriatal dopaminergic system

The effect of vasopressin, oxytocin and the C-terminal tripeptide of oxytocin, prolyl-leucyl-glycinamide (PLG), were tested on rotational behavior, following unilateral 6-OHDA-enduced lesion of the dopaminergic cell bodies in the substantia nigra. Intraventricular injection of lysine8-vasopressin, oxytocin or PLG caused ipsilateral (towards the lesioned side) rotation, as did peripheral administration of amphetamine. Direct local microinjection of the peptides into the substantia nigra on the intact side was without effect. The data suggest that posterior pituitary neuropeptides (vasopressin and oxytocin) caused presynaptic activation of the nigrostriatal dopaminergic terminals.