Effects of several monoamine-related compounds on the reserpine-induced spikes recorded from the medial nucleus trapezoides in rabbits.

Effects of several monoamine-related compounds on the reserpine-induced spikes recoreded from the medial nucleus Trapezoides (reserpine-induced Tr spikes) in rabbits were investigated. 5HTP (30--50 mg/kg, i.p.) showed marked suppression of reserpine-induced Tr spikes. Parachlorophenylalanine (PCPA) alone induced spikes similar to reserpine-induced Tr spikes after repeated doses (250 mg/kg twice daily for 3 successive days). A marked enhancement of the generation of reserpine-induced Tr spikes was elicited, when reserpine was given to rabbits pretreated with PCPA. L-DOPA (30--50 mg/kg, i.p.) showed a slight but significant suppressive action 20 to 40 min after injection. alpha-methyl-p-tyrosine (alpha-MT) (200 mg/kg, i.p.) produced no significant change within 6 hr, but did show a marked facilitatory effect on the generation of the spikes when reserpine was given to rabbits pretreated with alpha-MT. alpha-methyl-metatyrosine (alpha-MMT) (100 mg/kg, i.v.) caused a long-lasting, marked suppression. These findings suggest that both catecholamines and 5HT have a suppressive action on the generation of reserpine-induced Tr spikes.