The effect of antidepressant treatment on N-acetyl aspartate levels of medial frontal cortex in drug-free depressed patients

Neurochemical alterations in adolescent bipolar depression: a proton magnetic resonance spectroscopy pilot study of the prefrontal cortex

OBJECTIVE

Identifying neurochemical alterations in adolescent bipolar depression may enhance our understanding of the neurophysiology of bipolar disorder across the age spectrum. The objective of this study was to compare in vivo neurometabolite concentrations in bipolar adolescents with a depressed episode and healthy adolescents using proton magnetic resonance spectroscopy ((1)H MRS).

METHOD

Bipolar adolescents with a depressed episode (n = 28) and healthy adolescents (n = 10) underwent a (1)H MRS scan. Anterior cingulate (ACC) and left and right ventral lateral prefrontal (LVLPFC, RVLPFC) metabolite concentrations were calculated and compared between groups using analysis of covariance (ANCOVA).

RESULTS

ANCOVA showed significant group differences in ACC N-acetyl-aspartate (NAA) (F(1,33) = 17.8, p = 0.0002), LVLPFC choline (Cho) (F(1,32) = 13.1, p = 0.001), creatine/phosphocreatine (Cr) (F(1,32) = 18.5, p = 0.0002), and NAA (F(1,32) = 13.6, p = 0.0008), and RVLPFC Cr (F(1,32) = 9.6, p = 0.004), mI (F(1,32) = 11.1, p = 0.002), and NAA (F(1,32) = 11.4, p = 0.002) concentrations. In general, the bipolar depressed group had higher neurometabolite concentrations than the healthy group.

CONCLUSIONS

There may be localized alterations in brain neurometabolites in adolescents with bipolar depression. Limitations include lack of bipolar adolescents in other mood states and potential confounding effects of prior psychotropic medication use. Confirmatory (1)H MRS studies in larger samples of youths with bipolar depression are needed.

In vivo proton magnetic resonance spectroscopy in patients with mood disorders: a technically oriented review

Proton MR spectroscopy (1HMRS) has been extensively used among mood disorders patients. A review of the published literature in 1HMRS studies of mood disorders was carried out for the period 1991 to July 2006. Of 71 1HMRS studies, 77.5% were done at 1.5T and 66.2% used single voxel sequences (SVS), implying limitations of spectral resolution and anatomic coverage, respectively. In all, 47.9% of studies relied on creatine (Cr) as internal signal standard, although Cr changes were reported in major depression (MD). Most reported metabolic alterations related to mood state affected the left frontal lobe. Depressed adult and pediatric MD patients had reduced glutamate (Glu) in frontal lobe regions, which reversed with successful treatment. A consistent reduction of N-acetyl-aspartate (NAA) was reported in the hippocampal formation among bipolar disorder (BD) patients, along with an increment in frontal Glu. The differences in results of 1HMRS studies in mood disorders reflect heterogeneity of technical factors and subject selection. Future studies should benefit from higher spectral resolution and more extensive anatomic coverage as well as standardized data-processing protocols and subject selection criteria.

Deficit of perineuronal oligodendrocytes in the prefrontal cortex in schizophrenia and mood disorders

OBJECTIVE

A deficit of oligodendrocytes has been reported in the prefrontal cortex (PFC) in schizophrenia (SCH), bipolar disorder (BPD) and major depression (MDD). Also, a decreased size of pyramidal neurons has been detected in layer III in SCH and in mood disorders. Since oligodendrocytes have a trophic influence on neurons, reduced neuronal size reported in these disorders might be associated with the deficit in subpopulation of perineuronal oligodendrocytes. We hypothesized that deficit of perineuronal oligodendrocytes might occur in SCH and mood disorders.

METHOD

We estimated the number of oligodendroglial satellites of pyramidal neurons and the size of pyramidal neurons in layer III (Brodmann's area 9) in Nissl stained sections in SCH, BPD, MDD and normal controls. The Stanley Foundation Neuropathology Consortium brain collection consisted of 15 cases in each of four groups was used.

RESULTS

We detected a prominent and significant reduction in the number of perineuronal oligodendrocytes in the sublayers IIIa, IIIb and IIIc in SCH, BPD and MDD as compared to controls. The BPD group differed significantly from SCH group and from MDD group. There were no significant differences in somal sizes of pyramidal neurons in the sublayers IIIa, IIIb, IIIc between each of the psychiatric groups and the control group. Only BPD group showed significantly smaller neuronal size in sublayer IIIc as compared to controls.

CONCLUSIONS

Our data provide evidence for a deficit of perineuronal oligodendrocytes in severe mental disorders that may play a key role in the pathophysiology of SCH, BPD and MDD.

Reduction in occipital cortex gamma-aminobutyric acid concentrations in medication-free recovered unipolar depressed and bipolar subjects

BACKGROUND

Studies using proton magnetic resonance spectroscopy (MRS) have indicated that unmedicated, acutely depressed patients have decreased levels of gamma-aminobutyric acid (GABA) in occipital cortex. Cortical levels of glutamate (Glu) may be increased, although these data are less consistent. The aim of this study was to use MRS to determine whether changes in GABA and Glu levels were present in patients with mood disorders who had recovered and were no longer taking medication.

METHODS

An [1H]-MRS was used to measure levels of GABA, of the combined concentration of Glu and glutamine (Gln), and of N-acetylaspartate (NAA) in occipital cortex in medication-free, fully recovered subjects with a history of recurrent unipolar depression (n = 15), bipolar disorder (n = 16), and a group of healthy controls (n = 18).

RESULTS

Occipital levels of GABA and NAA were significantly lower in recovered depressed and bipolar subjects than in healthy controls, whereas Glu +Gln concentrations were higher.

CONCLUSIONS

Our data suggest that recovered unmedicated subjects with a history of mood disorder have changes in cortical concentrations of GABA, NAA, and Glu +Gln. These biochemical abnormalities may be markers of a trait vulnerability to mood disorder, rather than neurochemical correlates of an abnormal mood state.

The biochemistry of dysfunctional emotions: proton MR spectroscopic findings in major depressive disorder

Key neural systems involved in the processing and communication of emotions are impaired in patients with major depressive disorder (MDD). Emotional and behavioral symptoms are thought to be caused by damage or dysfunction in specific areas of the brain that are responsible for directing attention, motivating behavior, and learning the significance of environmental stimuli. Functional brain studies with positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) give support for functional abnormalities in MDD that are predominantly located in areas known to play an important role in the communication and processing of emotions. Disturbances in emotional processing as they are observed in MDD, if any, have very subtle morphometrical brain correlates. With proton magnetic resonance spectroscopy (1H MRS), brain metabolites can be measured noninvasively in vivo, thus furthering the understanding of the effects of changes in neurotransmitters within the brain. The current literature on 1H MRS studies in MDD is small with a large diversity of MRS methods applied, brain regions studied, and metabolite changes found. Nevertheless, there is strong evidence that changes in neurometabolite concentrations in MDD occur within brain regions, which are involved in the processing and communication of emotions that can be monitored by 1H MRS. This review summarizes the literature about biochemical changes quantified via 1H MRS in MDD patients in brain regions that play an important role for the communication and processing of emotions.