Antagonism of 5-Hydroxytryptamine by Methiothepin shown in Micro-electrophoretic Studies of Neurones in the Lateral Geniculate Nucleus

THERE has been little success in the search for a specific antagonist of the actions of 5-hydroxytryptamine (5-HT) on central neurones, although several compounds reduce the effects of both tryptamine derivatives and catecholamines in the central nervous system^1,2. The recent report that lysergic acid diethylamide blocked the excitant action of 5-HT, but not that of noradrenaline, on medullary reticular neurones³ has not been confirmed⁴. Moreover, an earlier investigation of olfactory bulb neurones indicated that lysergic acid diethylamide blocked the action of noradrenaline more readily than that of 5-HT⁵.