[Inhibitory effect of haloperidol on evoked dopamine release from striatal slices of the rat]

Haloperidol-induced changes in evoked dopamine (DA) release from striatal slices in rats were investigated. The dose-response curves for haloperidol to changes in the evoked DA release were found to be biphasic (small doses increased the release and large doses inhibited), which were shifted to the left by longer periods of superfusion with haloperidol. This rapid tolerance or inhibition of haloperidol-induced increases in evoked DA release was reduced or attenuated by the superfusion with acetylcholine (ACh) antagonists or B-HT920 and was enhanced by ACh agonists. The microinjection of kainic acid into the rat striatum 4 days before the experiment reduced the rapid tolerance or inhibition of the haloperidol-induced increase in evoked DA release. These data indicate that intrinsic ACh neurons in the striatum may play an important role in the induction of the rapid tolerance or inhibition of haloperidol-induced increase in evoked DA release from striatal slices in rats.