Prefrontal glutamate abnormalities confined to established psychosis

By Eleanor McDermid, Senior medwireNews Reporter

Abnormalities in glutamate and glutamine (Glx) levels in the prefrontal cortex are only present in patients with chronic schizophrenia, say researchers.

Hidenori Yamasue (The University of Tokyo, Japan) and colleagues found significant reductions in patients with chronic schizophrenia, but not in those at ultrahigh risk for psychosis or with first-episode psychosis.

“These reductions are potentially related to changes in glutamatergic transmissions and regional neuronal integrity and may be related to the pathophysiology and progressive brain morphological changes seen in schizophrenia,” the team writes in Schizophrenia Bulletin.

Yamasue et al used proton magnetic resonance spectroscopy to examine metabolite levels in the prefrontal cortex, selecting, based on previous studies, an area primarily incorporating the anterior cingulate and paracingulate gyri bilaterally.

In this area, levels of Glx and of N-acetylaspartate (NAA) were significantly reduced in 25 patients with chronic schizophrenia relative to 28 demographically matched controls. By contrast, there were no differences in levels of these metabolites between 24 patients at ultrahigh psychosis risk and 26 controls or between 19 patients with first-episode psychosis and 19 controls.

The researchers note that decreased NAA and Glx levels could relate to the reductions in brain tissue that occur in chronic schizophrenia. But they say that this cannot entirely explain the phenomenon, because their findings were adjusted for between-group differences in tissue composition.

Also, they found that levels of glycerophosphocholine plus phosphocholine, and of myoinositol, were no different from those in controls for any of the patient groups.

This is consistent with previous research and may suggest that “brain tissue loss occurs as a result of reductions of neuropil and potential rearrangements of cortical architecture, rather than by neuronal loss or degeneration,” says the team.

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