Stephan F K, Davidson A J
Department of Psychology, Florida State University, Tallahassee 32306-1270, USA.
Physiol Behav. 1998 Nov 15;65(2):277-88. doi: 10.1016/s0031-9384(98)00166-8.
To study the ability of single macronutrients to entrain or phase shift the feeding entrainable circadian oscillator, rats with lesions of the suprachiasmatic nucleus were first maintained on a single daily meal of lab chow until robust anticipatory approaches to the feeder or anticipatory wheel running was established. The meal time was then delayed by 8 h and chow was replaced with a 25-mL solution of 0.2% saccharin or 25 mL of saccharin plus 15 g of glucose. For other phase shifts, rats received either 6 mL of vegetable oil or mineral oil for 2 consecutive days. Consumption of about 6 g (24 kcal) or more of glucose resulted in robust delaying transients on the days after ingestion, whereas saccharin induced only small delays consistent with the initiation of a free-running rhythm with a period greater than 24 h. Surprisingly, consumption of 5.5 g of vegetable oil (47 kcal) did not result in delays greater than those in rats receiving mineral oil. The introduction of oil also produced a severe reduction in approaches to the feeder which could be alleviated by placing inaccessible chow in the feeders between oil meals. Phase shifts with oil were repeated with rats housed in wheels using anticipatory wheel running as a phase marker to assess whether the lack of phase shifts with fat was apparatus dependent. As was the case with approach behavior, anticipatory wheel running was not significantly delayed by vegetable oil consumption. These results indicate that a simple monosaccharide, glucose, has zeitgeber properties for the feeding entrainable oscillator. Vegetable oil, despite a higher caloric content, may be ineffective because of slower gastric emptying and nutrient absorption or because fat is not a good zeitgeber for the feeding entrained circadian oscillator.
为研究单一宏量营养素对进食可调节昼夜节律振荡器的诱导或相位调整能力，首先让视交叉上核受损的大鼠每日仅进食一顿实验室饲料，直至其对喂食器出现强烈的预期性趋近行为或预期性转轮运动得以确立。然后将进餐时间推迟8小时，并用25毫升0.2%的糖精溶液或25毫升糖精加15克葡萄糖取代饲料。对于其他相位调整，大鼠连续两天接受6毫升植物油或矿物油。摄入约6克（24千卡）或更多葡萄糖会在摄入后的几天内导致强烈的延迟瞬变，而糖精仅引起与启动周期大于24小时的自由运行节律相符的小延迟。令人惊讶的是，摄入5.5克植物油（47千卡）并未导致比接受矿物油的大鼠更大的延迟。引入油还导致对喂食器的趋近行为严重减少，通过在油餐之间在喂食器中放置无法获取的饲料可缓解这种情况。使用预期性转轮运动作为相位标记，对置于转轮中的大鼠重复进行油引起的相位调整，以评估脂肪缺乏相位调整是否与实验装置有关。与趋近行为的情况一样，植物油的摄入并未显著延迟预期性转轮运动。这些结果表明，一种简单的单糖葡萄糖对进食可调节振荡器具有授时特性。植物油尽管热量含量较高，但可能因胃排空和营养吸收较慢，或者因为脂肪不是进食调节的昼夜节律振荡器的良好授时因子而无效。
