Printed in Ct. Britain.
OF TRIFLUOPERAZINE UPON WHEEL-RUNNING ACTIVITY OF RATS
R. WONGand S. K. LEE Department of Psychology, University of British Columbia, Vancouver 8, Canada (Accepted 30 August 1971) Summary-Rats in group A were injected with 0.9 % NaCl solution while those in group B received trifluoperazine. Six hours later, these injected animals from both groups were placed in individual activity wheels and a measure was taken of their activity over a 2-hr period. After each test trial the rats were returned to their home cage and fed. Following 8 test trials the animals were given 5 additional test trials in which the conditions were reversed. Rats in group A received trifluoperazine while those in group B were injected with saline. The results clearly showed that trifluoperazine depressed the motor activity of rats in a running wheel. This effect was demonstrated between independent groups receiving either the drug or the saline injections and was also evident in the immediate decline in running activity when the rats were switched from saline to trifluoperazine injections. ALTHOUGH there has been a substantial number of experiments demonstrating the effects of chlorpromazine upon animal behaviour (HARTLAGE, 1965), much less is known about the
effects of a related phenothiazine,
A recent experiment by
ANGERMEIER,PHELPS, REYNOLDSand DAVIS (1968) has shown that injections of trifluoperazine
impaired the performance of rhesus monkeys in a discrimination learning, match-to-sample task. This effect was attributed to the hypothesis that the drug reduced the animals’ sensitivity to shock delivered whenever they made incorrect responses. The present authors believe that a simpler explanation is in order. It is quite likely that trifluoperazine did not have a direct effect upon the sensory input nor upon the learning or associate ability of the monkeys, but instead, decreased their level of spontaneous activity, thus resulting in impaired performance. The present study was designed to test the effects of injections of trifluoperazine (Stelazine, SKF) on the wheel-running activity of male rats. The animals received daily i.p. injections of either trifluoperazine or 0.9 % NaCl solution and were tested for 8 days. Then the conditions were reversed so that rats which formerly received trifluoperazine were given saline and vice versa. This “crossover” design was used in order to control for the possibility that the temporal order or sequential effects of the drug might influence the results. All rats were fed 15 g of Purina chow a day. This is about 7.5% of their normal food consumption. If the adaptation of the animal to the apparatus is a factor which affects the activity score, there is a strong possibility that unless the rats were rewarded for running after the test period they would show a decrease in activity with each successive day. The animals were therefore fed after they had completed their runs. This procedure treats the running response as an instrumental activity which is strengthened by food reward. 137
R. WONGand S. K. LEE
METHODS The subjects were 16 male Wistar albino rats. They were about 120 days old at the beginning of the experiment and weighed about 300 g. They were randomly assigned to either group A or group B. Throughout the experiment the rats were individually housed in 20 x 10 x 1Ocm wire mesh cages. Water was available at all times through a bottle placed at the top of the cage. Running activity was measured in activity wheels (Wahmann Company, Baltimore, Md.). The rats could either stay in the small cage adjoining the wheel or enter the wheel. The rats were given 8 daily test trials. Those in group A were injected with 1 ml 0*90/, NaCl solution while group B animals received 1 ml trifluoperazine solution (2.5 mg/kg). Six hours after these injections animals from both groups were placed in the individual activity wheels, left there for 2 hr, then removed, and a reading was taken from the counter attached to the wheel. After each test trial the animals were returned to their home cages where they were fed and were not disturbed until the following day. Following the first 8 test trials the animals were given 5 additional test trials in which the conditions were reversed. Rats in group A received trifluoperazine injections while those in group B were injected with saline. The injections were always given at 4 p.m. and the tests were given at 10 p.m. This time interval was chosen because previous findings indicated that the peak activity of trifluoperazine occurred 6 hr after administration (MOYER,1959). Throughout the course of the experiment the rats were living under a 24-hr light cycle. The previous generation from which the animals came were raised by the supplier under continuous illumination. It was for this reason that the rats were maintained under similar lighting conditions.
RESULTS AND DISCUSSION A graphic presentation of the results is shown in Fig. 1 which plots the activity scores of the group A and group B rats. It can be seen that the activity scores of the group B (trifluoperazine) animals were uniformly low over the first 8 test days in contrast to the progressive
Group A (trifluoperozine)
FIG. 1. Activity scores of rats injected with O-9 % NaCf solution or with tri~uo~raz~ne.
and rat motor activity
increase in activity of the group A (saline) rats. This observation was supported by an analysis of variance which showed a significant interaction between drug and days [F(7,98)=6*77; P <0*05]. The statistical analysis also indicated significant effects due to drug [F(1,14)=9+55; P