Cadmium induced hypothermia in mice: dose dependent tolerance development

The i.p. injection of Cd in mice will produce a dose related hypothermic response. The Cd appears to make the animals poikilothermic and their body temperature will approach the ambient temperature at which they are housed. The cause for this hypothermic action of Cd is not known, but we have demonstrated in our experiments that the effect may be partially related to a direct effect within the brain. In addition, the repeated injection of a low Cd dose (0.62 mg/kg) i.p. once daily for 3 days results in a profound tolerance to the Cd. A high dose (1.25 mg/kg i.p. once daily X 3 days) of Cd did not result in a similar tolerance phenomenon and a single injection of the high Cd dose 120 hr prior to the repeated low Cd dose regimen resulted in an obtunded tolerance response to the low dose. We propose that the higher Cd dose may have damaged the blood-brain barrier and this could account for the results we have observed.