Abstract
The purpose of the study reported here was to investigate changes in revolving activity in the rat following transition from ad libitum feeding to a 23-hr. per day deprivation cycle.
The Ss were seven male albino rats, aged about 90 days at the beginning of the experiment. The apparatus consisted of four activity wheels equated for frictional torque by the method of O. L. LACEY. Each wheel with a small, stationary living cage, located in a soundproof box, was always illuminated by 2 cp. lamp throughout the experiment. The temperature record in the box throughout the experiment averaged 20°C with a range of 19° to 23 °C.
The experiment was conducted in two sessions (Sept. -Nov. '59 and Feb. -Apr. '60) with conditions duplicated as similarly as possible. Each of these equivalent sessions consisted of two successive phases : (a) the four rats were first given a 15-day ad libitum feeding phase in the activity wheels. Food and water were always available, replenished at 1 : 00 P. M. (b) There followed a 30-day food deprivation phase during which food was available from 1 : 00 P. M. through 2 : 00 P. M. each day. Water was continuously available. The number of revolutions for every two hours interval was read by each counter at 1 : 00 P. M., thus the total number of revolutions per an activity wheel was provided by 12 counters.
The ad libitum feeding phase and the food deprivation phase are both divided into 5-day periods. Table 1 presents the means of individual means of revolutions in each 2-hr.-interval for successive 5-day periods. The percentages of revolving activity performed in each 2-hr.-interval during three 5-day periods under the ad libitum feeding schedule are presented in Fig. 1. This form of curve clearly indicates the nocturnal cyclic activity which is relatively stable. But, as would be seen in Fig. 2 which indicates the percentages of revolution under the condition of 23-hr. food deprivation during the first three 5-day periods (1-15 days), the type of the nocturnal cyclic activity is gradually changed. The most clear-cut change is found in the activity during the 2-hr. (11 : 00 A. M. -1 : 00 P. M.) just preceding the daily feeding. This consistent change is clearly shown in Fig. 3 which presents the percentages of revolution in the succeeding three 5-day periods of 23-hr. food deprivation (16-30 days). The results shown in these Figures may suggest that the progressive increase in prefeeding activity is due primarily to the increase in habit strength of the running response.
