Facilitatory effect of ketamine on punished behavior

Abstract

In order to compare the effect of ketamine on punished and unpunished operant responding with that of pentobarbital and amphetamine, pigeons were trained to perform under a multiple fixed-interval 5 min, fixed-interval 5 min (shock) schedule of food presentation. In both schedule components, the first response after 5 min produced access to grain (F15). In the punished component every response was followed by electric shock delivery. Lower effective doses of ketamine (1.7–5.6 mg/kg) caused moderate increases in punished FI responding with little or no alteration of unpunished response rates. Higher doses (10 and 17 mg/kg) decreased both punished and unpunished FI rates. Large increases in punished responding were caused by 10 mg/kg of pentobarbital. This and lower doses of the latter drug also moderately increased non-punished FI responding. The highest dose of pentobarbital used (17 mg/kg) decreased unpunished FI response rates while still increasing punished FI rates. Amphetamine caused dose-dependent decreases in punished responding at doses (0.17–1.0 mg/kg) that did not affect unpunished responding. Higher doses (1.7 and 3.0 mg/kg) of amphetamine also decreased unpunished FI rates, but to a lesser extent than punished response rates. From these and other reported results it may be concluded that ketamine affects schedule controlled behavior in characteristic ways, different from both minor tranquilizers and amphetamine-like drugs.