Effects of peripherally restricted ? opioid receptor agonists on pain-related stimulation and depression of behavior in rats.
Negus SS, O'Connell R, Morrissey E, Cheng K, Rice KC. Effects of peripherally restricted ? opioid receptor agonists on pain-related stimulation and depression of behavior in rats. J Pharmacol Exp Ther. 2012 Mar; 340(3):501-9.