Influence of long-term treatment with the Ca 2+-antagonists nifedipine, verapamil, flunarizine and with the calmodulin antagonist trifluoperazine on β-adrenoceptors in rat cerebral cortex

Abstract

1. 1. The binding of [ 3H]dihydroalprenolol ([ 3H]DHA) to β-adrenoceptors in cerebral cortex membranes (fraction P 2) was studied after 13-day oral treatment of male Wistar rats with the Ca 2+-antagonists nifedipine (20 mg/kg), verapamil (50 mg/kg), flunarizine (10 mg/kg) and with the calmodulin (CaM)-antagonist trifluoperazine (TFP) (3 mg/kg). 2. 2. A significant reduction in the number ( B max) of binding sites for [ 3H]DHA was established after the 3 Ca 2+-antagonists as well as after TFP. 3. 3. No changes in the affinity values ( K d ) [ 3H]DHA binding were found in all treated groups. 4. 4. The fluidity characteristics of the cerebral cortex membranes in nifedipine- and flunarizine-treated rats did not differ from those in controls. 5. 5. Based on these results, we concluded that long-term treatment with Ca 2+-and calmodulin-antagonists might induce changes in the central adrenergic mechanisms.