SCOPOLAMINE REVERSAL OF TREMOR PRODUCED BY LOW-DOSES OF PHYSOSTIGMINEIN RATS - EVIDENCE FOR A CHOLINERGIC MECHANISM

In order to provide evidence for the involvement of cholinergic mechan isms in low-dose physostigmine-induced tremor, a novel technique for m easuring forelimb tremor in rats was used. Rats that were administered physostigmine (0.05 and 0.1 mg/kg, s.c.), scopolamine (0.1 and 0.2 mg /kg, s.c.), and combinations of the two drugs, pressed a force-sensing operandum while a computer measured force output and performed Fourie r analyses on resulting force-time waveforms. When given alone, both d rugs decreased task engagement but mutually antagonized this effect wh en given together. Physostigmine increased tremor as well as peak forc e, Scopolamine decreased tremor and force when administered alone and reversed physostigmine-induced increases in force and tremor. Physosti gmine's low-dose induction of increased tremor during rats' skilled fo relimb use appears to have a prominent cholinergic component. (C) 1997 Elsevier Science Ireland Ltd.