Tremor in cats: the effect of administration of drugs into the cerebral ventricles.

In cats, tremor produced by intraperitoneal pentobarbitone sodium or by intramuscular chlorpromazine was abolished by injection into the cerebral ventricles of a few gamma of adrenaline or noradrenaline, but not of other sympathomimetic amines or of anti-Parkinsonian drugs. Chloralose, urethane, calcium chloride, and magnesium chloride produced anti-tremor activity when administered in this way. When adrenaline or noradrenaline was perfused from a lateral ventricle to the aqueduct during pentobarbitone sodium tremor, tremor was inhibited when less than 1 mug. had been perfused. Adrenaline was at least four times as active as noradrenaline. Isoprenaline inhibited tremor when perfused in higher concentrations, but perfusion of ephedrine, amphetamine or of the anti-Parkinsonian drugs in high concentrations was ineffective. Perfusion of 2 mug. of chloralose or of 20 mug. of calcium chloride was sufficient to inhibit tremor. Intraventricular injections of 250 to 500 mug. of 5-hydroxytryptamine initiated tremor. Possible physiological implications of these findings are discussed.