The Ca++-antagonist nimodipine decreases and the Ca++-agonist Bay K 8644 increases catecholamine synthesis in mouse...

The effects of the Ca++-antagonist nimodipine and the Ca++-agonist Bay K 8644 on brain catecholamine synthesis in male albino mice were investigated in vivo. Nimodipine caused a dose-dependent reduction in the synthesis rate of dopamine and noradrenaline, measured as the accumulation of 3,4-dihydroxyphenylalanine (DOPA) after inhibition of the L-aromatic amino acid decarboxylase with 3-hydroxybenzylhydrazine (NSD 1015). In contrast, Bay K 8644 caused an increase in DOPA synthesis. Furthermore, Bay K 8644 dose-dependently antagonized the effect of nimodipine. It is suggested that nimodipine and Bay K 8644 induced these changes by interfering with neuronal Ca++ transport, thus arguing for a role of voltage operated Ca++ channels in normal nerve function.