Lasting Consistency of Cold Adaptability in Rats Reared in Cold for Many Generations

Abstract

1) Wistar rats were successively reared in cold at 5°C from 1969 to 1984. The historical changes observed in these rats were reported. 2) The cold-adapted rats reared in cold for 8 to 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 to 8 weeks (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 β-adrenoceptor blocker. 3) The de-adapted rats reared in warm at 25°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. 4) 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.