Role of brain amines in the fetal hyperpyrexia caused by tranylcypromine in LiCl-pretreated rats.

Tranylcypromine (TCP), a monoamine oxidase inhibitor, caused a fatal hyperpyrexia in rats pretreated with LiCl once a day for 4 days. Pretreatment with LiCl alone did not alter the level of serotonin (5-HT), dopamine (DA) and norepinephrine (NE) in the brain. In fatal hyperpyrexia caused by LiCl plus TCP, the brain 5-HT and DA levels were increased, whereas the brain NE level was decreased. Reserpine and alpha-methyl-p-tyrosine completely prevented the hyperpyrexia, but FLA-63 did not show any effect. The hyperpyrexia was completely prevented by p-chlorophenylalanine (PCPA) given 72 hours before TCP but not by PCPA given 24 hours before TCP. Haloperidol and chlorpromazine, DA receptor blockers, inhibited the fatal hyperpyrexia, while cyproheptadine and methysergide, 5-HT receptor blockers, did not. These results suggest that DA plays an essential role in the hyperpyrexia induced by the combination of TCP and LiCl in rats, but the involvement of 5-HT is inconclusive.