| Abstract: | The prototype σ opioid receptor agonist Nallyl-normetazocine (SKF 10,047) was injected into the third cerebral ventricle of conscious, unrestrained cats, and their temperature was monitored automatically from the retroperitoneal space. In a cold environment (0°C) a small, but not dose-related, hypothermia occurred after doses of 100–500 μg. This response was not antagonized by naloxone given intraventricularly either 15 min before or 1 hr after the opioid. A smaller hypothermia resulted after 250 μg SKF 10,047 when the environmental temperature was 22°C, whereas hyperthermia developed in a hot environment (34°C). Thus SKF 10,047 appears to allow body temperature to drift, upward in the heat and downward in the cold, a pattern indicative of thermoregulatory depression. These results are similar to those obtained in the first 2–3 hr after pentazocine administration, and they support a previous classification of the initial temperature response to centrally injected pentazocine as due to stimulation of σ opioid receptors. |
