Vacuous jaw movements and feeding deficits in rats with ventrolateral striatal dopamine depletion: possible relation to parkinsonian symptoms.

A series of experiments examined the effects of regional dopamine depletions produced by intrastriatal injections of 6-hydroxydopamine on voluntary and involuntary movements in rats. Depletion of dopamine in the ventrolateral striatum produced a substantial decrease in food intake, from which the animals recovered. Rats with dopamine depletions in anteroventromedial or dorsolateral striatum did not have significant feeding deficits. Rats with ventrolateral dopamine depletions showed no deficits in locomotor activity or rearing behavior; however, depletions of dopamine in dorsolateral striatum significantly reduced rearing. Vacuous jaw movements that resemble chewing were produced by dopamine depletion in the ventrolateral striatum, but not the anteroventromedial or dorsolateral striatum. Systemic administration of haloperidol (0.4 mg/kg) increased vacuous chewing responses in dopamine-depleted and control rats. Thus, vacuous chewing responses can result from reduced functional activity of striatal dopamine, and these responses share some characteristics with human parkinsonian symptoms. In addition, these data support the notion that the neostriatum is functionally heterogeneous and that the ventrolateral region is particularly important for oral motor control.