The effects of phencyclidine and ketamine on sensory thresholds and reaction times in the baboon.

Adult male baboons were trained on a reaction time procedure, and absolute thresholds and reaction times to both a 16.0 kHz pure tone and a white light were obtained. Acute IM injections of phencyclidine (0.0032 to 0.1 mg/kg) or ketamine (0.032 to 3.2 mg/kg) were given at the beginning of 2-hr test sessions. Phencyclidine had no effect on auditory thresholds, visual thresholds, or visual reaction times, but selectively elevated auditory reaction times. Ketamine, on the other hand, elevated auditory thresholds and both auditory and visual reaction times, while having no effect on visual thresholds. Ketamine was also less potent than phencyclidine in elevating auditory reaction times, and recovery from these impairments was evident during the two-hour test sessions for ketamine, but not for phencyclidine.