Tryptophan depletion does not lower brain GABA levels in healthy volunteers
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The ascending serotonin (5-HT) innervation of the cortex preferentially targets gamma-aminobutyric acid (GABA) inter-neurons and 5-HT-GABA interactions may be important in the pathophysiology of depression and the actions of antidepressant drugs (see Taylor et al. 2003). Consistent with the latter suggestion, treatment of depressed patients with selective serotonin re-uptake inhibitors (SSRIs) increases cortical GABA levels as measured by proton magnetic resonance spectroscopy (MRS) (Sanacora et al. 2002) and a similar trend was recently reported after venlafaxine treatment of subjects with cocaine dependence (Streeter et al. 2005). In healthy subjects, a single intravenous administration of the SSRI, citalopram (Bhagwager et al. 2004) increased GABA levels in occipital cortex. This latter finding suggests that an acute increase in 5-HT neurotransmission can increase cortical GABA activity in humans as it does in animals (Taylor et al. 2003). The aim of the present study was to...
KeywordsMagnetic Resonance Spectroscopy Gaba Level Amino Acid Mixture Cocaine Dependence Tryptophan Depletion
The study was supported by the Medical Research Council MRC. PJC is an MRC Clinical Scientist.