Magnetic resonance spectroscopy (MRS) is a non-invasive imaging technique that
can provide localised measures of brain chemistry in vivo. We
previously found that healthy volunteers receiving the selective serotonin
reuptake inhibitor, citalopram, daily for 1 week showed higher levels of a
combined measure of glutamate and glutamine (Glx) in occipital cortex than those
receiving placebo. The aim of this study was to assess if a similar effect could
be detected in the frontal brain region. Twenty-three healthy volunteers
randomised to receive either citalopram 20 mg or a placebo capsule daily for
7–10 days were studied and scanned using a 3T Varian INOVA system
before and at the end of treatment. Standard short-TE (echo time) PRESS
(Point-resolved spectroscopy) (TE = 26 ms) and PRESS-J spectra were acquired
from a single 8-cm3 voxel in a frontal region incorporating anterior
cingulate cortex. Glutamate and total Glx levels were quantified both relative
to creatine and as absolute levels. Relative to placebo, citalopram produced no
change in Glx or glutamate alone at the end of the study. Similarly, no effect
was seen on other MRS measures studied: myo-inositol, choline,
N-acetylaspartate and creatine. These data suggest that the
effects of serotonin reuptake to modify cortical glutamatergic MRS measures may
be regionally specific. This supports the potential for MRS in assessing
neuroanatomically specific serotonin-glutamate interactions in the human
brain