Comparison of changes in tryptophan and serotonin in regions of the hamster and the rat brain over a twenty-four hour period.

Groups of male golden hamsters and Sprague-Dawley rats were sacrificed at 4-h intervals over a 24-h period. Tryptophan and serotonin (5-HT) were measured in the telencephalon and brain stem and tryptophan was measured in serum. Highly statistically significant changes in tryptophan and 5-HT content were observed over the period of the day. Generally the changes were more clearly defined and were significant to a higher statistical level in the hamster than in the rat. Statistically significant changes were also observed in serum tryptophan. In the hamster the daily changes in serum tryptophan were coincidental with similar changes in tryptophan and 5-HT in the brain stem and tryptophan in the telencephalon. On the other hand, the changes in 5-HT in the hamster telencephalon were not well correlated with changes in tryptophan and serum tryptophan.