PCPA reduces both monoaminergic afferents and nonmonoaminergic synapses in the cerebral cortex

In order to examine the possible trophic, nontransmitter role of monoaminergic fibers in the adult CNS, synaptic structures were examined in different laminae of the somatosensory cortex of the rat following a p-chlorophenylalanine (PCPA)-induced decrease of monoamine. Synaptic densities were reduced in a dose-dependent fashion by 30-50% in the target area of monoamine fibers following four injections of PCPA made over a 1-week period. Although serotonin- and tyrosine hydroxylase-immunopositive profiles were frequently observed in all laminae of the cerebral cortex, only a few such profiles had the morphology of synapses. Therefore, virtually all of the reduction in synaptic structures following PCPA treatment involved nonmonoaminergic fibers.