Formation of time memory for temperature stimuli in rats

在固定时间内每天4~5h的温度刺激后，在大鼠和人的体温调节系统中可以形成对温度刺激的时间记忆，根据这种记忆，受试者在没有实际温度应激的情况下，体温调节功能会发生变化。我们研究了每日定时温度应激对大鼠脑内不同核团Fos蛋白表达的影响。将大鼠保持在12：12 LD循环中，只在一天的黑暗阶段的后半部分暴露于热或冷。对照组大鼠不暴露于温度应激。在12天的温度暴露计划后，他们被麻醉，并在一天的上半部分(M)、中半部分(N)或后半部分(A)取出大脑。脑组织切片，进行Fos蛋白免疫组织化学染色。对照组和冷暴露大鼠下丘脑视前前部Fos阳性细胞数在N期和A期较M期有所增加，而热暴露大鼠A期Fos阳性细胞数无明显增加。对照组视交叉上核内Fos阳性细胞数在暗期无明显变化，而冷热暴露组大鼠视交叉上核Fos阳性细胞数在暗期逐渐减少。Fos在室旁核也有类似的表达模式。Fos在视上核、乳房上核和乳房外侧核的表达在各组之间无差异。每日定时温度刺激似乎改变了大鼠几个脑核神经元活动的昼夜变化模式。

After daily temperature stimulus for 4 〜 5 hours limited to a fixed time, time memory for temperature stimuli can be formed in the thermoregulatory system of rats and humans and, according to the memory, thermoregulatory functions alter during the period when subjects were previously exposed to heat without actual temperature stress. We investigated the Fos protein expression in various nuclei in the brain in rats after subjection to daily timed temperature stress. Rats, kept in a 12 : 12 LD cycle, were exposed to heat or cold only in the last half of the dark phase of the day. Control rats were not exposed to temperature stress. After a 12-day temperature exposure schedule, they were anesthetized and their brains were removed in the first half (M), at the middle (N) or in the last half of the dark phase (A) of a day. The brain samples were then sliced and immunohistochemical staining for Fos protein was performed. In the control and cold-exposed rats, the number of Fos-positive cells in the preoptic anterior hypothalamus increased during the periods N and A compared to that of the period M, while it did not increase in the period A in the heat-exposed rats. The number of Fos-positive cells in the suprachiasmatic nucleus did not change in the dark phase in the controls, whereas it gradually decreased in the dark phase in the heat- and cold-exposed rats. A similar pattern of Fos expression was seen in the paraventricular nucleus. There were no differences in the Fos expression in the supraoptic, supramammilary and lateral mammilary nuclei among the groups. It seems that timed daily temperature stimuli alter the pattern of day-night variations of neuronal activities in the several brain nuclei in rats.