Polarity linked to platelet GABA, glutamate uptake in bipolar patients
MedWire News: Platelet uptake of gamma aminobutyric acid (GABA) and glutamate is influenced by the polarity of mood episodes in patients with bipolar disorder (BD), researchers report.
Writing in Bipolar Disorders, Stefano Pini (University of Pisa, Italy) and team explain: "GABA and glutamate are the major neurotransmitters of the human central nervous system, and each of them is released in almost half of all brain synapses.
"Because GABA is inhibitory and glutamate is excitatory, they are usually paired to achieve a coordinated balance between excitatory and inhibitory events."
They add: "Several studies suggest that alterations in both of these neurotransmitter systems may play a crucial role in the pathogenesis of a variety of neurological and psychiatric disorders, including BD."
To investigate whether mood polarity is associated with platelet uptake of these neurotransmitters in BD patients, the team enrolled 40 patients with the mood disorder and 15 age- and gender-matched mentally healthy individuals (controls).
Of the patients with BD, 15 were experiencing an episode of depression, 15 were euthymic, and 10 were experiencing a manic episode at the time of the study.
The Hamilton Depression Rating Scale (HAM-D) and the Young Mania Rating Scale (YMRS) were used to assess symptom severity in the BD patients.
In tests on blood samples collected from the participants, the researchers found that platelet GABA uptake was significantly increased in BD patients with a depressive episode and decreased in those with a manic episode compared with controls. There was no significant difference between euthymic BD patients and controls regarding GABA uptake.
Regarding glutamate, platelet uptake of the neurotransmitter was significantly increased in both euthymic BD patients and those with a manic episode compared with controls, whereas there was no significant difference between depressed BD patients and controls.
The team also notes that in patients with a manic episode there was positive correlation between GABA uptake and HAM-D scores and between glutamate uptake and YMRS scores.
Pini and team conclude: "We found a relationship between GABA- and glutamate-uptake levels and the polarity of episodes in patients with BD.
"Our data suggest that the functionality of both GABA and glutamate transporters could represent a useful neurobiological marker to characterize the real polarity of an index episode of illness in patients with BD."
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By Mark Cowen