Impact of amitriptyline on learning and memory

Background/aim: Amitriptyline belongs to class of known as tricycline antidepresant (TCA) that is being used to treat anxiety and depressive states. It may help improve mood and feelings of well-being, relieve anxiety and tension, help to improve sleep and increase energy level. The study investigated the effect of amitriptyline on learning and memory using eighteen (18) healthy Swiss mice of both sexes weighing 16 – 25 g. Method: The animals were divided into three (3) groups consisting of six (6) animals each. Group 1 served as the control group, Group 2 was administered with amitriptyline at a dose of 3 mg/kg body weight dissolved in 3 mls of distilled water, and used to test for learning, while Group three was also given similar administration like Group 2, but used to test for memory. All the animals were tested for learning and memory performance using Novel object recognition task and Morris water maze test. Results: The results obtained from the Novel object recognition task showed that there was a significant decrease (p < 0.05) in total object approach in acquisition trial of amitriptyline treated group when compared to the acquisition trial of the control group. There was a significant decrease (p < 0.05) in retention trial of amitriptyline group when compared to retention trial in the control group. There was a significant decrease (p < 0.05) in total duration exploring objects in acquisition trial of amitriptyline treated group when compared to the acquisition trial of the control group. There was a significant increase (p < 0.05) in total duration exploring objects in retention trial of amitriptyline treated group when compared to the retention trial of the control group. There was a significant decrease (p < 0.05) in the index of habituation of amitriptyline treated group when compared to the control group. The index of discrimination showed a significant increase (p < 0.05) in amitriptyline treated group when compared to the control group and a significant decrease (p < 0.05) in amitriptyline group when compared to the control group. In the Morris water maze test, Day 1 – 3 were for acquisition training, day 4 – 6 reversal training, day 7 the probe trial day and day 8 the visible platform day. During acquisition training in the Morris water maze test, there was no significant difference in Swim latencies in day 1 and 2. However in day 3, there was a significant increase (p < 0.05) in swim latency of group compared to control group and a significant decrease (p < 0.05) in swim latency of amitriptyline treated group compared to the control group. During reversal training in day 1, 2 and 3, there was no significant difference in swim latency among the three groups. Results for the retention quadrant in the probe trials showed a significant decrease (p < 0.01) in amitriptyline group when compared to the control group. Conclusion: Results suggest that amitriptyline impairs learning and memory functions.

Forward and Backward Associations in Learning Letter Sounds

20 preschool children were instructed in letter-sound correspondences in one of two ways. One group was presented with the letter symbol and asked to produce the sound, while the other group was presented with the letter sound and asked to point to the corresponding letter symbol in an array of letters. After the last acquisition trial, the children were given a reversal trial in which they were presented with the usual response and asked to produce the stimulus. Performance of both groups on the reversal trial was significantly lower than on the last acquisition trial.

Effects of Post-Trial Injections of Scopolamine and Eserine on Acquisition of a Simultaneous Brightness Discrimination

4 groups of rats were given injections of scopolamine, methylscopolamine, eserine or saline immediately following the completion of an acquisition trial on a brightness discrimination in a T-maze. Results indicated that eserine and scopolamine groups displayed little or no reduction in errors over 50 acquisition trials, while Ss treated with methylscopolamine or saline showed a marked reduction in errors over the last 15 trials. While the data can be interpreted in terms of a consolidation model of memory, a progressive increase in failures to eat on rewarded trials by groups receiving the centrally active drugs, indicates that side effects of these drugs probably played a role in learning impairments.