Aschoff J, von Goetz C
Max-Planck-Institut für Verhaltensphysiologie, Andechs, Federal Republic of Germany.
J Biol Rhythms. 1986 Winter;1(4):267-76. doi: 10.1177/074873048600100401.
Squirrel monkeys (Saimiri sciureus) were housed singly in cages equipped with a tree for climbing to measure locomotor activity, and with a movable food cup that could be arrested automatically. The animals were kept in continuous dim illumination (LL), twice interrupted by several weeks of entrainment by a light-dark (LD) 12:12 cycle. Apart from three control sections in which the food cups were unlocked continuously (ad libitum feeding), food was accessible for 3 hr per day only, with interfeeding intervals varying from 23 to 26 hr (periodic restricted feeding, or RF). During LD entrainment, the imposition of an RF schedule resulted in anticipatory behaviors, represented by increased tugs at the food cup and a pause in locomotor activity preceding the feeding time. In LL, the animals showed free-running circadian rhythms of locomotor and "feeding" activity that nearly always persisted when ad libitum feeding was replaced by RF. The period (tau) of the free-running rhythm was slightly modulated in relation to the varying interfeeding intervals (T), but entrainment was never achieved except in one test with an animal whose tau was very close to T. It is concluded that periodic availability of food represents an extremely weak zeitgeber, if any, for the circadian pacemaker of squirrel monkeys.
松鼠猴（松鼠猴属）被单独饲养在配备有供攀爬的树以测量运动活动的笼子里，还有一个可自动停止的可移动食物杯。动物被置于持续昏暗照明（LL）环境中，两次被为期数周的12:12明暗（LD）循环的同步化打断。除了三个食物杯持续解锁的对照组（自由进食）外，每天仅3小时可获取食物，进食间隔从23至26小时不等（周期性限制进食，即RF）。在LD同步化期间，实施RF时间表会导致预期行为，表现为在进食时间前食物杯被拉动次数增加以及运动活动暂停。在LL环境中，动物表现出运动和“进食”活动的自由运行昼夜节律，当自由进食被RF取代时，这种节律几乎总是持续存在。自由运行节律的周期（tau）相对于不同的进食间隔（T）略有调节，但除了对一只tau非常接近T的动物进行的一次测试外，从未实现同步化。结论是，食物的周期性供应对于松鼠猴的昼夜节律起搏器而言，即便算是一个授时因子，也是极其微弱的。
