Low doses of haloperidol interfere with rat tongue extensions during licking: a quantitative analysis

Orolingual dyskinetic effects of haloperidol were studied in rats trained to lick drops of water from a force-sensing disk. Haloperidol dose-dependently decreased force of tongue protrusion, decreased lick duration, increased interlick interval, and decreased number of licks. Fourier methods showed that haloperidol, in doses as low as 0.06 mg/kg, slowed the lick oscillations from an average of 5.250 Hz to 5.096 Hz (p = .014). Lick force was modulated by water drop delivery, but this effect was not influenced by haloperidol, which suggests no interference of the drug with sensory regulation of licking. The drug-induced deficits in tongue force may be manifestations of either postural alterations (pseudoparkinsonism) or orobuccolingual dyskinesias or both. Orolingual motor impairments may account for some of the neuroleptic-engendered behavioral decrements that have previously been explained in terms of reward, motivational deficits, or both.