Tryptophan analogues and sleep in rats

Rats implanted with EEG and EMG electrodes were intraperitoneally injected with 30 mg/kg of 5-methyl-DL-tryptophan, 5-bromo-DL-tryptophan, 5-benzyloxy-DL-tryptophan and L-N methyltryptophan and polygraphically recorded for 8 h. There were no changes in sleep or wakefulness except for the increased REM sleep latency produced by administration of 5-benzyloxy-DL-tryptophan. It appears from these findings that specific alterations of tryptophan's structure on C₅ or on the side chain are associated with the loss of tryptophan's hypnotic capacity.