The nonimmobilizer 1,2-dichlorohexafluorocyclobutane does not affect thermoregulation in the rat

Inhaled and other anesthetics profoundly affect the central nervous system, causing amnesia, immobility in the face of noxious stimulation, and depres sion of thermoregulation. Nonimmobilizers, inhaled compounds whose lipophil icity suggests that they should be anesthetics, do not produce immobility, but they do cause amnesia. Their effects on thermoregulation were the subje ct of the present study. We gave eight rats isoflurane on one occasion and the nonimmobilizer 2N (1,2-dichlorolhexafluorocyclobutane) on another. We m easured the effect of various concentrations of each compound on thermoregu lation provoked by body cooling. The specific outcome was increased metabol ism, as reflected in increased output of carbon dioxide. Isoflurane decreas ed the temperature threshold for such increases and the maximum response in tensity, doing so in a concentration-dependent manner, whereas 2N had a min imal or no effect at any concentration up to 0.9 minimum alveolar concentra tion (estimated from its lipophilicity). Thus, 2N may be a useful tool for studies of the mechanisms mediating the thermoregulatory depression produce d by anesthetics: 2N should not affect such a mechanism.