NALOXONE ALTERS LOCOMOTION AND INTERACTION WITH ENVIRONMENTAL STIMULI

Rats were injected with saline or naloxone (0.5, 5.0 or 25 mg/kg) and monitored for locomotion and both frequency and duration of contact with stimuli in a multicompartment exploratory chamber. Naloxone produced a dose-related reduction in locomotion and in frequency of contact with stimuli. At the lowest dose tested this reduction was accompanied by an increase in total duration of contact and in time spent per contact with the stimuli. In contrast, the highest dose of naloxone decreased the duration of contact with stimuli and induced prolonged periods of inactivity. An intermediate response was observed with 5.0 mg/kg naloxone. These results indicate that lower doses of naloxone may enhance interaction with environmental stimuli while the predominant effect of higher doses is a general suppression in behavioral activity. Similarities with the antimanic agent lithium chloride and possible clinical implications are discussed. © 1979.