Serotoninergic but not noradrenergic neurons in rat central nervous system adapt to long-term treatment with monoamine oxidase inhibitors.

Repeated administration of monoamine oxidase inhibitors induces a transient decrease in the firing rate of serotoninergic neurons followed by complete recovery, whereas it results in a persistent reduction of the firing rate of noradrenergic neurons. Under these conditions, serotoninergic, but not noradrenergic, neurons undergo a desensitization of their somatic autoreceptors. Serotoninergic neurons therefore show the capacity to free themselves from their autoregulatory control, a property which noradrenergic neurons appear to be lacking. The time course of the recovery in the firing rate of the serotoninergic neurons is consistent with the delayed antidepressant effect of monoamine oxidase inhibitors.