[Heart rates in male Wistar rats reared under different conditions of the weaning period and social housing].
A prior study reported the developmental changes in heart rate (HR) in male rats. In this paper, we carried out more laborious analyses to check and compare the differences among effects of the rearing conditions. In group-housed rats, the earlier the weaning periods, the lower the variance within litter, but the higher the variance between litters. In contrast to this, high values within litter were maintained in the earlier weaned isolates On the occasion, 18 G was close to 28 G in changes in the variance, and 18 I showed the same trends as 14 I, thus indicating the different significance of the periods of 14-18 days after birth and 18-28 days concerning the interaction of mother and offspring. The rats that interacted with both littermates and mother as 18 G and 28 G, showed the marked reduction in the variance between individuals along with age as opposed to 14 I, 18 I and 14 G in which the infantile form of higher variances were maintained after the 10 th week. A dynamic model of HR was led, which showed two distinct phases according to the changes in the variance. These phases corresponded to the development and aging stages. In addition, the implications of "intrinsic process", "immaturity" and "enriched environments" were discussed.
D000375:Aging; D000818:Animals; D006339:Heart Rate; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012931:Social Environment; D012934:Social Isolation; D014886:Weaning