Dopaminergic regulation of striatal cholinergic interneurons: an in vivo microdialysis study.

In vivo microdialysis was used to study the putative inhibitory effects of dopamine on cholinergic interneurons in the striatum of conscious rats. The dopamine receptor agonists apomorphine (0.3 and 3 mg/kg, s.c.) and (+/-)N-0437 (1.4 mg/kg, s.c. decreased interstitial concentrations of acetylcholine while increasing those of choline. In contrast, the dopamine receptor antagonists haloperidol (0.1 and 1 mg/kg, i.p.) and (+/-)sulpiride (20 mg/kg, i.p.) enhanced striatal acetylcholine output but had little effect on choline. Previously, a lack of effect of these drugs on striatal acetylcholine was reported. The main methodological difference between these studies was that the calcium concentration of the microdialysis perfusion solution was 3.4 mM in the former study versus 1.2 mM in the present experiments. The results of this study reemphasize the importance of the calcium concentration in determining the effects of drugs on central neurotransmitter release, and confirm a role of dopamine in the regulation of striatal cholinergic interneurons.