EFFECTS OF GENDER ON THE CENTRAL ACTIONS OF NEUROPEPTIDE-Y AND NOREPINEPHRINE ON VASOPRESSIN AND BLOOD-PRESSURE IN THE RAT

Neuropeptide Y (NPY) and norepinephrine are co-localized in the noradr energic projection from the A, nucleus of the medulla to the vasopress inergic magnocellular neurons of the supraoptic and paraventricular nu clei. Because this pathway is involved in the control of vasopressin r elease, we have examined the possibility that NPY and norepinephrine i nteract in this control. Because the stimulation of vasopressin releas e by the intracerebroventricular (i.c.v.) administration of norepineph rine is greater in male than in female rats, the experiments were carr ied out in conscious male rats and in female rats in the proestrous an d non-proestrous phases of the estrous cycle. NPY (940 pmol i.c.v.) ca used small sustained increases in plasma vasopressin concentrations th at were greater in proestrous than in non-proestrous females and males . Norepinephrine i.c.v. increased plasma vasopressin levels transientl y and to a greater extent in females than males. When NPY and norepine phrine were given together, the pattern of the vasopressin response wa s similar to that of norepinephrine alone. The magnitude of this respo nse in males and proestrous females did not differ from that to norepi nephrine alone; in non-proestrous females the response was twice that to norepinephrine alone. In non-proestrous rats, NPY also enhanced the presser response to norepinephrine. Thus, NPY interacts centrally wit h norepinephrine in vasopressin release and cardiovascular function an d this effect is dependent upon gender and phase of the estrous cycle.