Abstract

Morphine-dependent monkeys respond with large falls in body temperature to: 1) physical restraint; 2) the administration of nalorphine; and 3) abrupt withdrawal from morphine treatment. Thus, hypothermia is a characteristic of the classical forms of the morphine abstinence syndrome in monkeys. Restraint-induced hypothermia appears to be a special form of precipitated abstinence because it occurs only when restraint is imposed after a lapse of a few hours from a morphine injection and because it is reversed by morphine and other narcotic analgesics of six different chemical families, but not by other classes of drugs. Physostigmine also precipitates large falls in body temperature in dependent monkeys, of a magnitude 7 times larger than that of falls produced by this drug in non-dependent controls. This effect appears to be mediated peripherally because neostigmine also produces marked hypothermias in dependent monkeys and because the physostigmine effect can be blocked more effectively by methylatropine than by atropine. On the other hand, restraint-induced hypothermia can be reversed by atropine but not by methylatropine. The hypothermia precipitated by nalorphine is not prevented by atropine or methylatropine.