Inhibition of K+-evoked release of rat striatal 5-hydroxytryptamine by an atypical antidepressant: Trazodone

Using microdialysis, extracellular concentrations of 5-hydroxytryptamine (5 -HT) and 5-hydroxyindoleacetic acid (5-HIAA) were determined in the striatu m of rats. In rats given trazodone, m-chlorophenylpiperazine dihydrochlorid e, or imipramine, the concentrations of 5-HT were unchanged. 5-HIAA in traz odone- or imipramine-treated rats, however, was respectively, decreased to 80 or 65% of preinjections levels. When the potassium concentration (K+) wa s increased up to 150 mmol/l in the perfusate, the concentrations of 5-HT i ncreased to about ten times the basal levels in the rats given saline. In r ats treated with trazodone, K+-evoked elevations of 5-HT were less than fiv e times the basal level. Multiple trazodone administrations prolonged the d uration of inhibition of 5-HT release. In rats treated with other drugs, th e K+-evoked 5-HT release was not affected. These observations suggest that trazodone itself might reduce 5-HT neural transmission. Copyright (C) 2001 S. Karger AG, Basel.