What future for antidepressants?

The common mechanism of action of most tricyclic antidepressants is the inhibition of the reuptake of the biogenic amines norepinephrine, serotonin and dopamine. Another postulated mechanism of action for most is the down-regulation of beta-adrenergic receptors post-synaptically and [alpha]2 heteroreceptors on 5-HT terminals. Other produce down-regulation of 5-HT1and 5-HT2 receptors. Neither of these mechanisms fully account for a common antidepressant mechanism of action. Is it possible to unify these hypotheses of antidepressant action