Physostigmine as a discriminative cue in rats.

Rats, trained to respond differentially in a T-maze contingent upon the presence or absence of physostigmine (0.50 mg/kg), showed a reversal of drug responding when physostigmine (0.50 mg/kg) was given simultaneously with the anticholinergic ditran (dose range: 0.80-3.20 mg/kg). Testing the quaternary anticholinesterase neostigmine (0.50 mg/kg) resulted in no drug responding which indicates a central site of action for the physostigmine discrimination.