EFFECTS OF MORPHINE, CLONIDINE, AND INTENSITY CHANGE ON ELECTRIC‐SHOCK DISCRIMINATION

Abstract
The effects of morphine, clonidine and changes in stimulus intensity were examined in squirrel monkeys responding on 1 of 2 levers following brief presentations of 1 of 2 electric shock intensities (0.1 and 0.5 mA). Responses were designated as correct or incorrect depending on which shock intensity was presented and which lever was pressed. Morphine (0.42 to 1.80 mg/kg) and clonidine (0.075 to 0.18 mg/kg) decreased percentage correct responding. Morphine and clonidine also increased response latency and the number of shock presentations that were not followed by responses. Changes in shock intensity also decreased percentage correct respond, but had no effect on response latency or on the number of shock presentations not followed by responses.