Central administration of neuropeptide Y induces hypothermia in mice. Possible interaction with central noradrenergic systems

Neuropeptide Y (0.24 and 1.17 nmol icv) and clonidine (0.025, 0.05 and 0.1 mg/Kg ip) induced a slight decrease of short duration of the rectal temperature in mice in a dose-dependent manner. While pretreatment with yohimbine (0.5 mg/Kg sc), was without effect on neuropeptide Y-induced hypothermia, it attenuated the hypothermic effect of clonidine. The association of neuropeptide Y (0.05 and 0.24 nmol icv) with clonidine (0.0125, 0.025, 0.05 and 0.1 mg/Kg ip) induced a synergistic effect, but it only was significant when neuropeptide Y 0.05 and 0.24 nmol icv was associated with clonidine 0.1 mg/Kg ip and when neuropeptide Y 0.05 nmol icv was associated with clonidine 0.05 mg/Kg ip. These results suggest that the effect of neuropeptide Y is not mediated by an interaction on alpha 2-adrenoceptor, but in accordance with these results, the existence of a collaborative mechanism between both neuropeptide Yergic and noradrenergic systems cannot be ruled out.