VASCULAR-RESPONSES TO NEUROPEPTIDE-Y ARE GREATER IN FEMALE THAN MALE-RATS

Sex differences in vascular effects of neuropeptide Y (NPY) were inves tigated in isolated tail artery ring segments from male and female F34 4 rats. Both pre- and postjunctional effects of NPY appeared to be gre ater in females. NPY potentiated contractions elicited by transmurar a drenergic nerve stimulation (TNS), consistent with an effect on smooth muscle Y-1 receptors. The degree of potentiation was significantly gr eater in arteries from females than males. Ovariectomy of the females resulted in a decrease in potentiation, while orchiectomy of the males resulted in an enhanced NPY effect. When NPY potentiation was measure d in the presence of peptidase inhibitors, the effect of exogenous NPY was enhanced; however the enhancement was greater in arteries from fe males than either males or ovariectomized females. Possible male-femal e differences in inhibitory prejunctional Y-2 receptor function were a ddressed using the selective agonist NPY13-36 At a low frequency of st imulation (0.5 Hz), NPY13-36 inhibited the response to TNS in arteries from females and castrated males; however, NPY13-36 had no significan t effect on responses to TNS in arteries from males or ovariectomized females. Thus gonadal hormones appear to modulate several components i nvolved in NPY neurotransmission, including tissue peptidase activity, postjunctional Y-1 and prejunctional Y-2 receptors. These effects may contribute to significant differences observed in vascular reactivity be tween females and males.