An analysis of the effects of apomorphine and haloperidol on the release of [³H]-dopamine and [³H]-noradrenaline from rabbit brain slices

The effects of apomorphine and haloperidol on the K⁺-induced release of [³H]-dopamine from striatal slices and [³H]-noradrenaline from cerebellar slices were examined. Apomorphine (0.01-1 μM) reduced the K⁺-induced release of [³H]-dopamine from striatal slices, leaving the K⁺-induced release of [³H]-noradrenaline from cerebellar slices unaffected. A higher concentration (10 μM) of apomorphine increased significantly the K⁺-induced release of [³H]-noradrenaline from cerebellar slices. Haloperidol (0.01-1 nM) increased the K⁺-induced release of [³H]-dopamine from striatal slices, leaving the K⁺-induced release of [³H]-noradrenaline unaffected. Haloperidol in higher concentrations (10-100 nM) increased significantly the K⁺-induced release of [³H]-noradrenaline from cerebellar slices. Both compounds inhibited the uptake of [³H]-dopamine into striatal slices and [³H] noradrenaline into cerebellar slices. In low concentrations both compounds showed selectivity for dopaminergic receptor sites, apomorphine stimulating and haloperidol inhibiting pre-synaptic dopamine receptors. Higher concentrations of these compounds showed a non-selective action.