Pyridostigmine bromide alters locomotion and thigmotaxis of rats: Gender effects

Male rats and female rats in the proestrous and metestrous stages of estrus were tested to determine the effects of pyridostigmine bromide on locomoti on rate and thigmotactic response using doses of 3.0, 10.0, and 30.0 mg/kg. Thirty minutes after administration of the pyridostigmine bromide the rats were videorecorded for 2 h in a 1 m(2) open-field arena. The rats' activit ies were analyzed for the drug's effect on speed throughout the 2 h and dur ing six 20-min segments. Also, the times that the rats were observed moving through the central 50% of the arena were determined. Locomotion rates dec reased significantly, and thigmotaxses increased significantly in all group s of rats as a dose response to pyridostigmine bromide. Habituation occurre d over 2 h for both responses, primarily during the first 40 min. Female ra ts were more affected than males, but metestrous and proestrous females did not differ significantly in their responses. At the 30 mg/kg the effect wa s persistent throughout the test period. Proestrous females dosed at 30 mg/ kg had much higher pyridostigmine bromide serum levels than metestrous fema les and males. (C) 1999 Elsevier Science Inc.