[Heart rates in male Wistar rats reared under different conditions of the weaning period and social housing (author's transl)].
The electrocardiogram (ECG) was recorded from unrestrained rats reared under the 6 conditions: weaned on the 14th, 18th or 28th postnatal day and thereafter housed in isolation (14I, 18I and 28I) or grouped with littermates (14G, 18G and 28G). The heart rate (HR) was measured on a 30 second sample of the ECG recorded from the 5th to the 20th week of age. For all rearing conditions, HR was confirmed to follow the normal distribution in respective weeks, and changes in HR through development were investigated. (a) HRs of 14G and 18G were significantly higher at the 5th week, and were later to reach the stabilized HR than 28G and isolated rats. (b) The variability between individuals (Vbi) reduced markedly at the 7th week in 18G and 28G, this may be attributed to the reduction in the variance within litter (Vwl) due to the interactions among littermates. In isolated rats, it was a relative low value in Vbi perhaps because of a low value in the variance between litters (Vbl). Contrary to isolated rats, in 14G Vbi was high, Vbl was high as well, but Vwl was low owing to the early separation from the mother and long periods of group housing.
D000818:Animals; D004562:Electrocardiography; D006339:Heart Rate; D008297:Male; D008426:Maternal Deprivation; D051381:Rats; D011919:Rats, Inbred Strains; D012934:Social Isolation; D014886:Weaning