Effect of glucose on amphetamine-induced motor behavior

The effect of 1 g/kg D-glucose on amphetamine-induced increases in activity; stereotypy; and rotation in rats with unilateral 6-OHDA lesions of nigro-striatal neurons was examined. The amphetamine dose-response curve for stereotypy was shifted to the right by glucose but retained the same slope as the control curve, suggesting that glucose competes for amphetamine or dopamine receptors that mediate this behavior. The slope of the dose-response curve for activity was significantly decreased by glucose, suggesting that glucose reduces activity levels in a manner that is non-competitive with the action of amphetamine or dopamine. Amphetamine-induced turning was unaffected by glucose at all doses tested. These data suggest that the effect of amphetamine on each of the three motor behaviors may be mediated by different dopamine-containing neurons, or by different post-synaptic dopamine receptors. The findings are also consistent with other data suggesting that glucose antagonizes dopamine function, but they suggest that this antagonism may not be uniform over all dopaminergic neurons or receptor types.