Effect of chronic calcium antagonist treatment on dopamine recognition sites in rat striatum

The effects of nimodipine and flunarizine administration (18 days 15 mg/kg/day p.o.) on striatal dopamine recognition sites in rats were investigated in vivo. In vitro flunarizine but not nimodipine displaces [3H]spiroperidol binding. After in vivo treatment both drugs induce a significant increase in the number of sulpiride displaceable spiroperidol binding sites (flunarizine, +114%, nimodipine +61%) concomitant with an increase in the dissociation constant. Binding parameters return toward control values after 1 week of suspension of the treatment. The results suggest that the repeated in vivo treatment with nimodipine and flunarizine may significantly interact with dopaminergic transmission leading to adaptive changes of the dopamine recognition sites.