Acute and sub-acute effects of deltamethrin and chlordimeform on schedule-controlled responding in the mouse

The effects of deltamethrin (0.03-3 mg/kg) and chlordimeform (0.3-56 mg/kg) were examined on schedule-controlled responding in the mouse. The response (interruption of a photocell beam) was maintained under a fixed-interval (FI) 60-sec schedule of milk delivery. Acute doses of deltamethrin larger than 0.1 mg/kg decreased responding in a dose-related manner. The ED50 was approximately 1 mg/kg; 3 mg/kg abolished responding. Repeated administration of 3 mg/kg (once daily for 10 days) did not result in a change in the rate-decreasing effects of that dose; however, daily (pre-injection) control response rates decreased about 50%. When dosing was discontinued, rates of responding failed to completely return to pre-drug control levels. Acute doses of chlordimeform larger than 10 mg/kg decreased responding in all mice, but in mice not previously receiving drugs lower doses had a greater rate-decreasing effect. The ED50 was between 10-30 mg/kg; 56 mg/kg abolished responding. Repeated administration of 3 and 10 mg/kg had little effect. Repeated administration of 30 and 56 mg/kg abolished daily (pre-injection) control performances completely after 5-6 days. Responding gradually returned to control levels after dosing was discontinued. The behavioral toxicity of both chlordimeform and deltamethrin was augmented by repeated administration.