Hippocampus가 손상된 흰쥐의 갑상선기능

Abstract

The hippocampus was ablated through neocortex in a group of male albino rats(hippocampus group). Rats were also prepared in which only the portion of neocortex over the hippocampus was ablated(neocortex group). These rats together with normal control rats were studied on their thyroid activity before and following brain ablation in warm environment(28-30°C), and then also under reduced room temperature(1416° C). Following intraperitoneal administration of 10,uC of carrier-free 1131, the radioactivity of the thyroid was measured every morning and evening or every 24 hour for 120 to 144 hours. The thyroidal release rate of 1131 was calculated taking the 48th hour radioactivity as 100% and was expressed in the form of effective half life, which served as an index of the thyroid activity. Under 28-30°C, the effective half life tended to prolong after brain damage compared with that of preoperative period both in hippocampus group(N: 8, Mean±S.D. : 54.2±9.29 hr before, 72.6±23.10 after) and also in neocortex group (N: 8, Mean±S.D.: 50.5 ±8.24 hr before, 61.6±20.80 after). But the difference was of dubious significance in hippocampus group(.05 <p<.10) and insignificant in neocortex group(p>.20). Nor was there any significant difference between hippocampus group and neocortex group as regards the net increment of effective half life following brain lesion. For reference, the mean effective half life of three normal control rats under the same environment throughout was 53.8 hr in the preoperative period, and 51.6 hr in the postoperative period. In another experiment, where hippocampus group, neocortex group, and normal control group were subjected to reduced room temperature(14-16°C), the thyroid activity was found significantly accelerated in all groups. The differences in the effective half life among these three groups, however, were negligible and statistically insignificant under low temperature (N : 12 in each group, Mean±S.D.: 42.7±6.37 hr in normal control group, 46.3±7.21 in hippocampus group, and 43.2±5.83 in neocortex group). These three groups had been equated as regards their thyroid activity in the preoperative period under 28-30 0C. The inferences from these data are that the hippocampus and neocortex might exert slight, inconspicuous facilitatory influence upon thyroid activity in warm weather, but that these brain structures seems to exert little influence upon accelerated thyroid function in cold weather.