no changes were found in the concentration of tryptophan ( trp ) , 5-hydroxytryptophan ( 5-htp ) , 5-hydroxytryptamine ( 5-ht ) or 5-hydroxyindole acetic acid ( 5-hiaa ) in the cerebrospinal fluid ( csf ) of male rats either before sexual activity , immediately after ejaculation of after the postejaculatory refractory period ( pei ) .
C0041249
tryptophan
C0000578
5-htp