The effects of paradoxical sleep deprivation and valine on spatial learning and brain 5-HT metabolism

We have previously reported that rapid eye movement sleep deprivation (REMS D), induced by the flower pot technique, causes a deficit in reference spat ial memory and increases rates of serotonin (5-HT) metabolism in the brain. In this study we used increased concentrations of dietary valine to inhibi t tryptophan (TRP) transport across the blood-brain barrier in an attempt t o modify the REMSD-induced increase of 5-HT metabolism Rats were fed either a control diet or the same diet supplemented to 2% by weight valine, and w ere allocated to one of three experimental groups: cage control (CC), stres s tank control (TC), or REMSD. Reference and working spatial memory of all rats was tested in a Morris water maze on Days 2, 3, and 4. REMSD produced a significant decrement in reference memory on Days 2 and 4, independent of dietary condition. The valine diet had a detrimental effect on the referen ce memory of LTC rats on Day 2 but not Day 4. Measurements made on Day 4 in dicated that the valine diet decreased brain TRP only in the CC rats. Tn co ntrast, the valine diet did not prevent increases in brain TRP or 5-HT meta bolism in REMSD rats, and increased hypothalamic and brain stem TRP concent rations and the hippocampal 5-HIAA/5-HT ratio in TC rats. These results ind icate that dietary valine does not prevent REMSD-induced changes in spatial memory or serotonin metabolism although it does reduce brain TRP in nonstr essed rats. (C) 1999 Elsevier Science Inc.