Comparative effects of trazodone and tricyclic antidepressants on uptake of selected neurotransmitters by isolated rat brain synaptosomes

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Abstract
The effect of trazodone, a new antidepressant agent, on uptake of serotonin (5-HT), norepinephrine (NE), and dopamine (DA) by crude synaptosome preparations from rat hypothalamus was compared with imipramine, desipramine, and clomipramine. Trazodone was determined to be a very selective inhibitor of the 5-HT uptake mechanism with IC50 values of 5.67×10-7, 3,54×10-5, and 5.25×10-5 M, for 5-HT, NE, and DA uptake, respectively. Clomipramine, the only other selective inhibitor of 5-HT uptake studied, had IC50 values of 7.59×10-9, 1.12×10-7, and 2.51×10-7 M, for 5-HT, NE, and DA, respectively. Although less potent, trazodone was 4±0.6 times more selective than clomipramine in its ability to inhibit synaptosomal uptake of 5-HT with respect to NE. This selectivity for the 5-HT uptake mechanism is consistent with the clinical antidepressant efficacy of trazodone.