"Cyproheptadine and LSD, two known antagonists of the peripheral effects of 5-HT, were administered i.v. to conscious rabbits at different times before the intracerebroventricular (i.c.v.) administration of 5-HT, NAD or dopamine. Cyproheptadine (which had a slight hypothermic effect) antagonized the rise in temperature induced by 5-HT; this antagonism was dose-related and appeared to be specific in that the hyperthermia induced by noradrenaline or dopamine was hardly modified. Interactions between LSD (which is hyperthermic alone) and 5-HT were more complex — both potentiation and depression being observed."