Central hyperthermic effect of arsenic in rabbits.

Hyperthermic effect of arsenic was investigated in rabbits. Injections of arsenic trioxide (0.0001 to 0.1 micrograms) into a lateral cerebral ventricle of the rabbit evoked a dose-dependent hyperthermia, respiratory stimulation and peripheral vasodilatation. Heat loss through respiratory stimulation and peripheral vasodilatation appeared responsible for the long latent period and the slight hypothermia sometimes obtained during this period as these effects followed the same time course. These effects were centrally mediated as demonstrated by the lack of efficacy of the same doses by the intravenous route. The hyperthermic effect of arsenic was antagonized by the sulphydryl donator, dimercaprol, the a-adrenoceptor blocking agent-phenoxybenzamine and the PG-synthesis inhibitor-aspirin. Multiple sites, for antagonistic effects of these substances can be explained by the action of arsenic in inactivating sulphydryl containing enzymes which are many and catalyze diverse biochemical reactions.