Changes in schedule-controlled response and schedule-induced drinking after cholinergic blockers in rats.

The effects of the tertiary cholinergic blockers atropine sulfate (AT) and scopolamine hydrobromide (SCOP), and the quaternary cholinergic blockers atropine methylnitrate (AT-Mt) and scopolamine butylbromide (SCOP-Bt), on operant response (lever-pressing) and adjunctive drinking in the rat developed under a fixed interval (FI) 1.5 min food reinforcement situation were investigated. The tertiary compounds, particularly SCOP, increased total responses, and produced a dose-related decrease in the index of curvature (IC) for local rates of response during the FI. The quaternary compounds, however, did not produce changes in the total responses and the IC for local rates of response. AT, AT-Mt and SCOP suppressed adjunctive drinking, while SCOP-Bt did not. AT and SCOP, but not AT-Mt and SCOP-Bt, decreased the IC for local rates of drinking. AT-Mt suppressed drinking at a uniform rate throughout the FI. In addition, several doses of AT and SCOP tended to increase licking counts at the drinking spout per 1 ml water intake. The present results suggest that central cholinergic blockade increases the response and suppress adjunctive drinking, and that the peripheral cholinergic blockade suppresses only adjunctive drinking. Moreover, central cholinergic blockade may produce changes in the patterns of response and drinking during the FI, and in the manner of drinking at the drinking spout.