[Iprindole: a functional link between serotonin and noradrenaline systems?]. / Iprindole: lien fonctionnel entre systèmes sérotoninergique et noradrénergique?

Iprindole is an active antidepressant in clinical practice but its mechanism of action has never been clearly defined. Serotoninergic regulation of noradrenergic neurons of locus coeruleus depends on 5-HT2 receptors. This regulatory action of the 5-HT system appears to facilitate the down-regulation of beta receptors. In behavioural tests involving the noradrenergic system, the role of iprindole, administered in subactive doses, was evaluated in the presence of subactive doses of fluvoxamine, a serotonin uptake inhibitor. Yohimbine is an alpha2 antagonist, inducing a dose-dependent toxicity. This test allows a rapid and selective screening of antidepressants with direct and indirect beta-agonist properties. Administration of iprindole displayed a toxicity of fluvoxamine in the presence of yohimbine. A 5-day pre-treatment of iprindole antagonized this potentiation unmasked after acute administration of iprindole. The down-regulation of beta receptors induced by a chronic treatment by iprindole could prevent the adrenergic expression of yohimbine's toxicity. But the down-regulation of 5-HT2 receptors also obtained with chronic treatment by iprindole, can explain this antagonism preventing fluvoxamine's action. Hypothermia induced by a high dose of apomorphine, depends on an activation of the noradrenergic system. During the interaction with fluvoxamine, iprindole unmasked an antagonism of this hypothermia due to apomorphine. The activity of a subactive dose of salbutamol, a direct beta-agonist, was evaluated in the presence of fluvoxamine on hypothermia induced by a high dose of apomorphine. The aim of this interaction was to define the beta-adrenergic property of iprindole more precisely.(ABSTRACT TRUNCATED AT 250 WORDS)