The enhanced brain availability of tryptophan, as a consequence of exogenous tryptophan administration, can increase neuronal serotonin synthesis and this can interfere with brain function. The deprivation of REM-sleep (D) constitutes another external factor that can change brain excitability, facilitating in some cases the manifestation of neurological diseases like epilepsy. Here we used cortical spreading depression (CSD) as a neurophysiological parameter to investigate, in the adult rat brain, the effects of a single L-Tryptophan intraperitoneal injection combined or not with 72h D-condition (water-tank technique). A 1h baseline CSD-recording was performed under 1g/kg+40mg/kg urethane+chloralose anesthesia, and revealed increased (P