Hypothermic effect of cocaine in rats

Cocaine injected intraperitoneally into rats resulted in a dose-dependent hypothermia. Intracerebral injection of smaller doses also produced a fall in body temperature. In rabbits and guinea-pigs, cocaine produced hyperthermia, in mice and chicks it produced hypothermia while inconsistent changes were produced in goats. Pre-treatment of rats with 6-hydroxydopamine, alpha-methyl-m-tyrosine or haloperidol significantly antagonized the cocaine hypothermia. Pre-treatment of the rats with either hyoscine or methscopolamine resulted in some but non-significant attenuation of the cocaineinduced hypothermia. Pre-treatment with p-chlorophenylalanine, however, did not modify the cocaine hypothermia. Pargyline pre-treatment significantly antagonized the hypothermic action of cocaine. It is suggested that cocaine may cause the release of noradrenaline centrally or it may potentiate its action by interfering with the uptake mechanism. It is also possible that cocaine may have a direct effect on the heat regulating centre in the hypothalamus.