Different effects of the calcium antagonists nimodipine and flunarizine on dopamine metabolism in the rat brain

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Abstract
The effect of two calcium antagonists, nimodipine and flunarizine, on striatal dopamine (DA) metabolism in rats was compared. Flunarizine (5–20 mg/kg i.p.) caused a dose-dependent increase in the DA metabolite, 3,4-dihydroxyphenilacetic acid (DOPAC) in the caudate nucleus. Following the 20 mg/kg dose, DOPAC levels were maximally elevated by about 50% from 2 to 12 hrs after treatment. On the contrary, nimodipine at the dose of 20 mg/kg i.p. produced a modest decrease in DOPAC levels. Neither calcium antagonist modified DA content. However, both nimodipine and flunarizine, at the dose of 20 mg/kg, markedly reduced the accumulation of DOPAC in the caudate nucleus induced by haloperidol (1 mg/kg). It is suggested that flunarizine, but not nimodipine, has a neuroleptic-like action, whereas the two calcium antagonists have in common the ability to attenuate the hyperactivity of DA neurons.