EFFECTS OF NIMODIPINE ON BIOGENIC-AMINES IN DISCRETE BRAIN-AREAS

Discrete rain sections were obtained from rats after once or repeatedly given intraperitoneal nimodipine at doses ranging from 2.5 to 40 mg/kg. The single or the last treatment was carried out at 2-8 h before killing. The biogenic amine and metabolite content of the tissue samples were determined by high-performance liquid chromatography with electrochemical detection. The nimodipine-induced effects, chiefly regarding the brainstem, the thalamus-midbrain and the striatum, consisted of both an increase in 5-hydroxyindoleacetic acid (5-HIAA) levels and a decrease in dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) levels. Since the 5-HIAA/5-hydroxytryptamine (5-HT) ratio was increased, whereas the DOPAC/dopamine (DA) and HVA/DA ratios were decreased, it was argued that nimodipine activated the serotonergic and inhibited the dopaminergic systems. The first effect was enhanced by fasting and, likewise, by drug administration repeated for 5 days, while the second was not affected by fasting, but disappeared after 5 days' treatment. The data obtained appeared to substantiate the usefulness of nimodipine to treat some disorders of the central nervous system.