Naloxone antagonism of electrical stimulation induced tail erection in mice

Tail erection was induced by focal electrical stimulation of the mesencephalic central gray through chronically implanted electrodes in mice. The response was current intensity dependent. Pretreatment with naloxone (5 mg/kg IP), a specific narcotic antagonist, abolished tail erection produced by low electrical current. In contrast, the tail response elicited by higher current was only partially blocked by naloxone. The results suggest that electrical stimulation induces tail erection by releasing an endogenous opioid peptide from the mesencephalic central gray.