Serotonin and norepinephrine transporter binding profile of SSRIs.

Even today, pharmacotherapy for mood disorders is based almost entirely on the observation in the 1950s and 1960s that agents that enhance monoamine transmitter activity are effective antidepressants. Preclinical studies have shown that long-term administration of nearly all effective antidepressants increases the efficiency of postsynaptic serotonin transmission; many also modify central noradrenergic activity. For the majority of antidepressants, these changes are the result of their ability to block serotonin and/or norepinephrine activity at their "presynaptic uptake sites" (i.e., at the serotonin transporter [SERT] or the norepinephrine transporter [NET]). Drugs that are highly selective for one transporter over another have been demonstrated to be effective and tolerable, whereas agents that act on multiple transporters may not necessarily achieve better efficacy and may result in additional adverse events. The rationale for the use of drugs that affect multiple transports is based on the suggestion that antidepressants that block both the SERT and the NET may provide better efficacy. This can only be determined through empirical studies.