THE DECREASE OF SEROTONIN RELEASE INDUCED BY A TRYPTOPHAN-FREE AMINO-ACID DIET DOES NOT AFFECT SPATIAL AND PASSIVE-AVOIDANCE LEARNING

We assessed whether consumption of a diet lacking in tryptophan (TRP) resulted in alteration in learning and memory performance and hippocam pal 5-HT release in rats. Two hows after the acute administration of T RP-free (T) and balanced (B) diet rats were trained in a one-trial pas sive avoidance task. The two groups of rats showed no significant diff erence in retention latencies. Two other groups of rats, fed with the above diets during the acquisition of a radial-arm maze task, showed n o difference in baseline performance. The acute ingestion of the T die t produced a significant and long lasting decrease of hippocampal and cortical 5-HT release in rats when compared to the B diet, while the 1 2th day of the T diet, 5-HT was not detectable in the dialysate. These data indicate that the diminished brain release of 5-HT induced by a T diet is not sufficient to impair cognitive processes. (C) 1997 Elsev ier Science B.V.