Dual inhibitory action of trazodone on dorsal raphe serotonergic neurons through 5-HT1A receptor partial agonism and α1-adrenoceptor antagonism

Autoři: Alberto Montalbano aff001;  Boris Mlinar aff001;  Francesco Bonfiglio aff001;  Lorenzo Polenzani aff002;  Maurizio Magnani aff002;  Renato Corradetti aff001
Působiště autorů: NEUROFARBA—Dipartimento di Neuroscienze, Psicologia, Area del Farmaco e Salute del Bambino, Università di Firenze, Firenze, Italia aff001;  Angelini RR&D (Research, Regulatory & Development), Angelini S.p.A, S.Palomba-Pomezia (Roma), Italia aff002
Vyšlo v časopise: PLoS ONE 14(9)
Kategorie: Research Article
doi: 10.1371/journal.pone.0222855


Trazodone is an antidepressant drug with considerable affinity for 5-HT1A receptors and α1-adrenoceptors for which the drug is competitive agonist and antagonist, respectively. In this study, we used cell-attached or whole-cell patch-clamp recordings to characterize the effects of trazodone at somatodendritic 5-HT1A receptors (5-HT1AARs) and α1-adrenoceptors of serotonergic neurons in rodent dorsal raphe slices. To reveal the effects of trazodone at α1-adrenoceptors, the baseline firing of 5-HT neurons was facilitated by applying the selective α1-adrenoceptor agonist phenylephrine at various concentrations. In the absence of phenylephrine, trazodone (1–10 μM) concentration-dependently silenced neurons through activation of 5-HT1AARs. The effect was fully antagonized by the selective 5-HT1A receptor antagonist Way-100635. With 5-HT1A receptors blocked by Way-100635, trazodone (1–10 μM) concentration-dependently inhibited neuron firing facilitated by 1 μM phenylephrine. Parallel rightward shift of dose-response curves for trazodone recorded in higher phenylephrine concentrations (10–100 μM) indicated competitive antagonism at α1-adrenoceptors. Both effects of trazodone were also observed in slices from Tph2-/- mice that lack synthesis of brain serotonin, showing that the activation of 5-HT1AARs was not mediated by endogenous serotonin. In whole-cell recordings, trazodone activated 5-HT1AAR-coupled G protein-activated inwardly-rectifying (GIRK) channel conductance with weak partial agonist efficacy (~35%) compared to that of the full agonist 5-CT. Collectively our data show that trazodone, at concentrations relevant to its clinical effects, exerts weak partial agonism at 5-HT1AARs and disfacilitation of firing through α1-adrenoceptor antagonism. These two actions converge in inhibiting dorsal raphe serotonergic neuron activity, albeit with varying contribution depending on the intensity of α1-adrenoceptor stimulation.

Klíčová slova:

Antidepressants – Cell membranes – Drug administration – Neurons – Sleep – Serotonin receptors – Serotonin – Partial agonists


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