Serotonin and norepinephrine: long-term decrease in rate of synthesis in brain of rats primed with p-chlorophenylalanine.

Rats which had been primed with the serotonin depletor, p-chlorophenylalanine, and sacrificed months later were found to have the same resting levels of brain serotonin and norepinephrine as unprimed controls. However, when treated with the monoamine oxidase inhibitor, tranylcypromine, the former showed a significantly lower accumulation of these biogenic amines than their tranylcypromine-treated unprimed counterparts. These findings indicate that brain serotonin, which had been lowered at the outset by p-chlorophenylalanine, had returned to normal levels but that the priming procedure might have resulted in a long-term decrease in the turnover rates of serotonin as well as norepinephrine. Primed animals may prove suitable as models of disturbed biogenic amine metabolism with possible relevance to schizophrenia and other brain dysfunctions.