Abstract
The effects of (−)-propranolol, (+)-propranolol and (±)cyanopindolol on the release of [ 3H]5-hydroxytryptamine ([ 3H]5-HT) were investigated in synaptosomes from the hippocampus of the rat, depolarized in superfusion with 15mM KCl. (−)-Propranolol, but not (+)-propranolol, inhibited in a concentration-dependent way the K +-evoked release of [ 3H]5-HT. (±)-Cyanopindolol behaved similarly but was about 10 times more potent than (−)-propranolol. The inhibitory effects of (−)-propranolol and (±)-cyanopindolol were prevented by the autoreceptor antagonist methiothepin. Both β-adrenoceptor antagonists antagonized the inhibition by exogenous 5-HT of the K +-evoked release of [ 3H]5-HT. The data suggest that some β-adrenoceptor antagonists may behave as mixed agonists-antagonists at the 5-HT autoreceptor. Synaptosomes in superfusion appear to be particularly suitable to study separately agonistic compared to antagonistic activity of compounds having a mixed agonist-antagonist profile.
Published Version
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