TRYPTOPHAN METABOLISM IN MALE SARDINIAN ALCOHOL-PREFERRING (sP) AND -NON-PREFERRING (sNP) RATS

Parameters of tryptophan (Trp) and related metabolism were comparedin male Sardinian alcohol-preferring (sP) and -non-preferring(sNP) rats. Liver Trp pyrrolase activity was 38–58% higherin sP than in sNP rats, and this was associated with a greaterexpression of the enzyme mRNA as measured by multiprobe oligonucleotidesolution hybridization. Moderately (about 10–19%), butsignificantly, lower concentrations of free serum, total serum,and brain Trp were also observed in sP compared with sNP rats.Concentrations of whole brain 5-hydroxytryptamine (5-HT) andits major metabolite 5-hydroxyindol-3-yl-acetic acid (5-HIAA)were, however, 14–21% higher in sP rats. Serum corticosteroneconcentration was 18% higher in sP rats. We conclude that alcoholpreference in Sardinian rats is associated with increased liverTrp pyrrolase activity and mRNA expression leading to a decreasein Trp availability to the brain. Although a simple serotonindeficiency could not be demonstrated in the whole brain, thepossibility could not be ruled Out that a deficiency may bepresent in discrete areas of the brain of the sP rat.