Effects of cycloalkyl ring analogs of phencyclidine on behavior in rodents

The purpose of the present experiments was to evaluate the effects of eliminating or varying the size of the cycloalkyl ring of phencyclidine (PCP) from 3 to 8 carbons while leaving the composition of the benzene and piperidine rings unaltered. Compounds were evaluated for their effectiveness in producing PCP-like discriminative stimuli and changes in pupil diameter in the rat and impaired motor performance on the Rotarod in the mouse. All modifications of the cycloalkyl ring of PCP significantly reduced the relative potencies of the cycloalkyl analogs, shortened their duration of action and also modified their spectra of action, including their effectiveness in producing PCP-like discriminative stimuli and miosis in the rat as well as ataxia in the mouse. The present results demonstrate that the cyclohexyl moiety of PCP is an absolute requirement for producing a full PCP-like spectrum of activity.