The effects of DL-p-chlorophenylalanine and DL-alpha-methyl-p-tyrosine on the brain catecholamine, serotonin and free amino acid contents in rat.

The changes in the brain levels of catecholamines, serotonin and free amino acids have been considered as a factor in the development of the physical dependence on and tolerance to some drugs. In order to show the relationships among the brain levels of these substances, three groups of rats were given i.p. DL-alphaMpT alone, DL-pCPA alone, or DL-alphaMpT and DL-pCPA together, twice a day for three days. Another group was kept as control. The brain levels of catecholamines, serotonin and free amino acids were determined. Although DL-alphaMpT and DL-pCPA alone caused a decrease in the levels of catecholamines and serotonin respectively, the administration of DL-alphaMpT and DL-pCPA together did not. The changes in the levels of free amino acids which were found were related to the metabolism of catecholamines and serotonin.