Fig. 3. The amount of L-tryptophan (TRP) in the telencephalon (A), hypothalamus (B), optic tectum (C) and brain stem (D) of isolated juvenile rainbow trout fed feeds supplemented with L-tryptophan to a level corresponding to two (2X), four (4X) and eight (8X) times the L-tryptophan content of the non-supplemented control feed (1X). Stressed fish (filled square) were exposed to a standardised stressor (lowering the water level); non-stressed fish were undisturbed fish kept isolated (open triangle). Different letters indicate a significant difference at the P<0.05 level (LSD post-hoc test). Values are means ± S.E.M. from 5-7 individuals.