Effect of repeated treatment with tianeptine and fluoxetine on the central alpha(1)-adrenergic system

Tianeptine (TIA) is an antidepressant drug which enhances the reuptake of serotonin but, in contrast to tricyclics, shows no affinity for neurotransmitter receptors. The present study was aimed at determining whether repeated TIA treatment induced adaptive changes in the alpha(1)-adrenergic system, similar to those reported by us earlier for tricyclic antidepressants. The experiments were carried out on male mice and rats. TIA was administered at a dose of 5 or 10mg/kg once or repeatedly (twice daily for 14 days) and fluoxetine (FLU), used as a reference compound, at a dose of 10mg/kg. The obtained results showed that TIA administered repeatedly potentiated the methoxamine- and phenylephrine (PHEN)-induced exploratory hyperactivity in rats and clonidine-induced aggressiveness in mice, the effects mediated by alpha(1)-adrenoceptors. TIA given repeatedly (but not acutely) increased the binding (B(max)) of alpha(1)-adrenergic receptors in cerebral cortex for [(3)H]prazosin. However, the ability of the alpha(1)-adrenoceptor agonist PHEN to compete for these sites was not significantly changed. The above results indicate that repeated TIA administration increases the responsiveness of the alpha(1)-adrenergic system (behavioural and biochemical changes). On the other hand, FLU did not affect any behavioural and biochemical changes in this system.