Haloperidol-induced decrements in force and duration of rats' tongue movements during licking are attenuated by concomitant anticholinergic treatment.

To investigate the hypothesis that haloperidol's impairment of tongue protrusion in rats is Parkinson-like, the effects of centrally active scopolamine hydrochloride (0.1 or 0.2 mg/kg, SC) were evaluated in 36 rats that were also administered haloperidol (0.06, 0.12, or 0.24 mg/kg, IP). Rats were trained to lick water from a force-sensing disk, and the peak force and duration of each tongue contact were recorded along with the number of licks emitted in a 2-min session. Scopolamine hydrochloride significantly reversed haloperidol-induced deficits observed for peak force, duration, and number of licks. When given alone, scopolamine hydrochloride decreased peak force and duration. Fourier methods showed that the basic rhythm of licking was slowed by scopolamine hydrochloride but not by haloperidol. Taken together, the data suggest that central nervous system dopaminergic-cholinergic interactions importantly modulate tongue dynamics in the rat in a manner consistent with such interactions in neuroleptic-treated human patients.