Effect of dimethyl sulfoxide on cooling rates of unrestrained rats

A total of 170 adult rats were exposed to 1°C, 15°C, and 25°C environments following ip injections of 3 to 6 g per kg of DMSO in saline. Shaved subjects receiving 3 g per kg of DMSO in a 1°C environment cooled to a body temperature of 10°C within 239 min; subjects receiving 6 g per kg of DMSO cooled to 10°C in 175 min. Shaved saline controls required 412 min to reach the same temperatures. Unshaved rats in a 1°C environment which were treated with 6 g per kg of DMSO cooled to 10°C within 383 min. Unshaved saline controls failed to become hypothermic. Shaved subjects injected with 6 g per kg of DMSO in an environment of 15°C gave a mixed response, a few maintaining normothermia, some cooling a few degrees and then rewarming, and 50% cooling to environmental temperatures. All controls remained normothermic. At an environmental temperature of 25°C, DMSO-treated animals dropped 3.6°C and then rewarmed. Control subjects remained normothermic. Each DMSO-treated group, therefore, manifested a significant disturbance of temperature regulation.