Hypothermic effect in rats of NAJA nigricollis venom: role of acetylcholine.

O. H. Osman, A. O. A. Elkhawad and M. Ismail. Hypothermic effect in rats of Naja nigricollis venom: role of acetylcholine. Toxicon15, 75–80, 1977.—Naja nigricollis venom produced a hypothermic effect when it was injected intraperitoneally into rats, while N. naja, N. nivea and N. melanoleuca venoms were ineffective. Similarly, when injected into the preoptic area and paraventricular nucleus of the hypothalamus, N. nigricollis venom produced a greater fall in body temperature. This hypothermic response was not modified by pretreatment with bromolysergic acid diethylamide, p-chlorophenylalanine, haloperidol, phentolamine, pimozide, or α-methyl-p-tyrosine. However, it was significantly antagonized by either central or peripheral hyoscine pretreatment. It is suggested that N. nigricollis venom may act by causing the release of acetylcholine in the hypothalamus which then mediates the hypothermia.