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Effects of thyroxine and methimazolum on thermosensitive neurons in preoptic/anterior hypothalamic area in rats

Wang Hongqi, Feng Jiadi, Yao Chengyu

Teaching and Research Section of Neijin, Guangzhou College of Traditional Chinese Medical. Guangzhou, China；Department of Physiology, Chinese Medical University. Shenyang

Abstract

The effects of thyroxine (subcutaneous injection) and methimazolum (intubation feeding) on thermosensitive neurons (TSN) in the preoptic/anterior hypothalamic (PO/AH) area in rats were observed.The ratio of warm-sensitive neurons (WSN) to cold-sensitive neurons (CSN) was 1.86:1 and thermo-insensitive neurons (TIN) to thermosensitive neurons (TSN)1:1.43 in the control group. The ratio of WSN to CSN decreased to 1.20:1 and the ratio of TIN to 1:2.36 in the thyroxine group, while the former increased to 2.40:1 and the latter decressed to 1:1.29 in the methimazolum group. There was significant difference among three groups,[X_(2)=9.64,P<0.05]. Thirty-two percent of neurons (11/34) showed higher firing rates(>15Hz) in the control group, only 8% (3/37) in the thyroxine group and 9% (3/32) in the methimazolum group. In addition, the tolerance of TSN to warming stimulation was obviously lower in both pathological groups, as compared with the control group. The results suggest that a rise or fall of body temperature
in rats with subcutaneous injccting thyroxine and intubation feeding methimazolum may be related to the changes of proportion and excitability of PO/AH neurons, and that the disturbance of thyroxine synthesis, release and metabolism may interfere temperature regulation at the level of hypothalamus.

Key words: Temperature-regulation;Thermosensitive neuron;Preoptic/anteror hypothalamic area;Thyroxine;Methimazolum

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Citing This Article：

Wang Hongqi, Feng Jiadi, Yao Chengyu. Effects of thyroxine and methimazolum on thermosensitive neurons in preoptic/anterior hypothalamic area in rats. Acta Physiol Sin 1990; 42 (3): (in Chinese with English abstract).