Lasting consistency of cold adaptability in rats reared in cold for many generations.

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Abstract
Wistar rats were successively reared in cold at 5.degree. C from 1969-1984. The historical changes observed in these rats were reported. The cold-adapted rats reared in cold for 8-11 successive generations (C8-11G) were examined on their cold tolerance and nonshivering thermogenesis. C8-11G rats showed greater nonshivering thermogenesis than that of the warm-adapted control group (W) and rats exposed to cold for periods of 2-8 wk (C). The nonshivering thermogenesis of C8-11G rats was diminished to a similar level to that of W and C rats by administration of a ganglion blocker, of reserpine or of .beta.-adrenoceptor blocker. The de-adapted rats reared in warm at 25.degree. C for 3 generations after being reared for many generations in cold (DA-3G) showed much more nonshivering thermogenesis as compared to W rats. Cold tolerance of DA-3G rats was at a level of intermediate between that of W and C rats. Brown adipose tissue (BAT) weight of DA-3G rats was similar to that of C rats, while chemical composition of BAT in DA-3G rats differed from that of C and W rats.