Dystonia is a neurological disorder characterized by involuntary movements. We examined striatal dopamine function in hyperactive transgenic mice generated as a model of dystonia. Evoked extracellular dopamine concentration was monitored with carbon-fiber microelectrodes and fast-scan cyclic voltammetry in striatal slices from non-transgenic mice, transgenic mice with a positive motor phenotype, and phenotype-negative transgenic littermates. Peak single-pulse evoked dopamine concentration was significantly lower in phenotype-positive mice than in non-transgenic or phenotype-negative mice, but indistinguishable between non-transgenic and phenotype-negative mice. Phenotype-positive mice also had higher functional D2 dopamine autoreceptor sensitivity than non-transgenic mice, which would be consistent with lower extracellular dopamine concentration in vivo. Multiple-pulse (phasic) stimulation (5 pulses, 10-100 Hz) revealed an enhanced frequency dependence of evoked dopamine release in phenotype-positive versus non-transgenic or phenotype-negative mice, which was exacerbated when extracellular Ca²⁺ concentration was lowered. Enhanced sensitivity to phasic stimulation in phenotype-positive mice was reminiscent of the pattern seen with antagonism of nicotinic acetylcholine receptors. Consistent with a role for altered cholinergic regulation, the difference in phasic responsiveness among groups was lost when nicotinic receptors were blocked by mecamylamine. Together, these data implicate compromised dopamine release regulation, possibly from cholinergic dysfunction, in the motor symptoms of this dystonia model.