Sleep deprivation is one of the only interventions that have consistently been demonstrated to produce rapid antidepressant effects. The mechanisms by which sleep deprivation brings about rapid antidepressant effects remain to be elucidated. It is noteworthy, however, that recent genomic and proteomic studies have shown that acute sleep deprivation rapidly brings about an upregulation of several mediators of neuronal plasticity, most notably CREB and BDNF. Intriguingly, these are the very same molecules that are upregulated by chronic antidepressants, and are believed to underlie the delayed therapeutic effects of most antidepressants. Additional investigation of the regulation of CREB and BDNF by sleep deprivation has revealed that these changes are critically dependent upon the activation of the noradrenergic system. This is particularly noteworthy, since the locus coeruleus (LC) noradrenergic projection is quiescent only during rapid eye movement sleep (REM), when the target tissues display their greatest sensitivity; indeed, the temporal dissociation between the firing of the LC noradrenergic neurons, and the sensitivity of its postsynaptic targets in the cortex may have considerable relevance for the antidepressant effects of sleep deprivation. In this context, biological rhythms have the capacity to temporally dissociate biochemical processes, and imposing a temporal coincidence on normally dissociated events can have striking and unexpected effects. Thus, it is our hypothesis that activating the normally quiescent noradrenergic system during REM sleep (i.e. when its postsynaptic target system displays its greatest sensitivity) will robustly upregulate CREB and BDNF, thereby bringing about a rapid antidepressant effect. We propose to activate the noradrenergic system during REM sleep by infusing an alpha(2) antagonist, yohimbine. Since it is our hypothesis that activating the noradrenergic system during REM sleep will bring about an antidepressant effect by a similar mechanism as sleep deprivation, we will "enrich" our sample with sleep deprivation responders in this pilot study.