EFFECTS OF COCAINE ON SIMPLE REACTION-TIMES AND SENSORY THRESHOLDS INBABOONS

The effects of chronic, daily administration of cocaine on auditory an d visual reaction times and thresholds were studied in baboons. Single intramuscular injections of cocaine hydrochloride (0.1 to 5.6 mg/kg) were given once daily for periods of 10 to 25 days, and were followed immediately by psychophysical tests designed to assess cocaine's effec ts on simple reaction times as well as on auditory and visual threshol d functions. Consistent reductions in reaction times were frequently o bserved over the cocaine dose range of 0.32 to 1.0 mg/kg; at higher do ses, either decreases or increases in reaction times were observed, de pending upon the animal. Lowered reaction times generally occurred imm ediately following the 1st day's cocaine injection, and continued thro ugh all subsequent days during the dose administration period, suggest ing little development of tolerance or sensitivity to these reaction-t ime effects. Reaction-time decreases showed a U-shaped dose-effect fun ction. The greatest decreases in reaction times occurred from 0.32 to 1.0 mg/kg, and produced an average reaction-time decrease of 10 to 12% . Concurrently measured auditory and visual thresholds showed no syste matic changes as a function of cocaine dose. Pausing was observed duri ng performance of the psychophysical tasks, with the length of total s ession pause times being directly related to cocaine dose.