IMAGING OF THE SEROTONERGIC SYSTEM - INTERACTIONS OF NEUROANATOMICAL AND FUNCTIONAL ABNORMALITIES OF DEPRESSION

For nearly three decades, evidence supporting a role for aberrant sero tonergic function in the pathogenesis of depression has accumulated; h owever, only recently have methodologies and radiotracers suitable for in vivo clinical assessment of depression become available. To dare, only a few neurochemical imaging studies have been performed in active ly depressed subjects. A preliminary study using single photon emissio n computed tomography (SPECT) has demonstrated decreased levels of ser otonin (5-HT) transporters in the midbrain regions of subjects with ma jor depression. Analysis of the 5-HT2 receptor using positron emission tomography (PET) has suggested that this, receptor may not be altered significantly in the depressed brain but may increase in response to antidepressant treatment. These findings are supported by studies in s econdary ''poststroke'' depression that have shown that elevations in 5-HT2 receptor density correlated with the alleviation of symptoms of depressed mood. With the rapid development of novel PET and SPECT radi otracers, future studies of the serotonergic system that evaluate pres ynaptic (5-HT transporter) and postsynaptic (5-HT1A and 5-HT2A recepto rs) markers and the interaction of synaptic levels of 5-HT with these sites will make profound contributions to the understanding of the rol e of the serotonergic synapse in the pathophysiology of depression. (C ) 1998 Society of Biological Psychiatry.