Serotonergic serotonin 2 receptor modulation on DOPAC and 5-HIAA levels in rat striatum and nucleus accumbens: microdialysis studies of freely moving rats.

1. In vivo microdialysis with microbore-HPLC/ECD was employed to examine and compare changes of monoaminergic metabolites, dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindoleacetic acid (5-HIAA) in the nucleus accumbens (NuAc) and the neostriatum (Str) of freely moving rats, following systemic administration of the specific 5-HT(2) analogue. 2. The 5-HT(2) agonist decreased DOPAC and 5-HIAA in both the NuAc and Str. However, the effect produced by apomorphine only decreased the DOPAC level in these two areas. 3. This effect did not occur in the rats that had been pretreated with the serotonin (5-HT) depleting agent. However, the effect was found in the rats that the striatal neurons had been damaged. 4. The 5-HT(2) effect regulated the mesencephalic dopamine (DA) synthesis/turnover only when entirely influenced by 5-HT. The striato-nigral feedback loop was not involved in this effect. Additionally, presynaptic relationship probably occurred between the 5-HT and its innervated DA pathways.