Venom obtained from the scorpion Leiurus quinquestriatus produced a pronounced hyperthermic response when injected intraventricularly into rabbits. The venom-induced hyperthermia differed from that of pyrogens by its rapid onset following intraventricular injection and by the absence of the hyperthermic response when the venom was injected intravenously. The hyperthermic response was not antagonized by the prior intraventricular or intravenous injection of scorpion antiserum. Similarly, it was not modified by treatment with either chloropromazine or phenylbutazone. Pretreatment of rabbits with diethyldithio-carbamate or reserpine conferred partial protection against the hyperthermic response to the venom, whereas pretreatment of the rabbits with p-chlorophenylalanine markedly potentiated the response. Pretreatment of the rabbits with methysergide, tolazoline and/or propranolol did not modify the hyperthermic effect of the venom. The venom may act by releasing noradrenaline in the anterior hypothalamus or by causing, in the posterior hypothalamus, a shift in the balance of sodium and calcium.
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