ネズミの自発的交替現象の研究 V

電気痙攣衝撃 (E. C. S.) の影響

抄録

The present experiment was undertaken to find the effect of electroconvulsive shock (E. C. S.) on spontaneous alternation in the rat.
After exploration and pretraining, 29 naive albino rats were given 11 successive free choice trials per day for 5 days in a T-maze with rewards on both sides. On the basis of percent alternation in this“pre-E. C. S.”period, rats were divided into the experimental group (19 rats) and the control group (10 rats).
For the experimental group, E. C. S. was administered at the rate of one per day for 15 days.
The measurement of alternation was continued in this“E. C. S. period”with the same procedure as in the“pre-E. C. S. period”. Intervals between the treatments of E. C. S. and the following tests of alternation were approximately 22 hours. The control group received the same numbers of pseudo-E. C. S. treatment instead of true E. C. S. treatment.
Results
1) The first treatment of E. C. S. produced a significant decrement in percent alternation (Fig. 1). The most decrement was found after the 4th treatment of E. C. S. Although percent alternation of the experimental group thereafter showed a tendency to recover as the treatment progressed, there was a significant difference between two groups even after the 15th E. C. S.
2) Three kinds of measurement were used to examine the relationship between the strength of position preference and the effect of E. C. S.
(a) Percent alternation with the inter-trial interval of 24 hours was increased by E. C. S. (Table 1).
(b) The mean number of turns to the side which each rat chose in more than half of the total 220 trials was decreased in the early stage of the “E. C. S. period” (Fig. 2). These results of (a) and (b) would indicate that the position preferences found in the“pre-E. C. S. period”might temporarily be destroyed by the treatment of E. C. S.
(c) However, the mean numbers of turns to the preferred side based on the daily trials were significantly increased by E. C. S. (Fig. 3). Moreover these scores corresponded reversely to percent alternation, that is, the more the animal showed the daily position preference, the lower was the percent alternation.
3) E. C. S. increased the running time, especially of the 1st daily run. This, however, would not explain the decrement of alternation, because on the 1st day of the“E. C. S. period”no significant difference was found in the running time between two groups.
4) Several signs of emotional behavior were found in the E. C. S. group.
From these results and many other results on behavior variability which concerned with cerebral function, emotion etc., it was assumed that both the functional decrement of the cerebral cortex and the excessive excitment of the lower centers of emotion would produce the decrement of behavior variavility. Electroconvulsive shock may be one of the causes which produce this kind of decrement.