The altered expression of α1 and β3 subunits of the gamma-aminobutyric acid A receptor is related to the hepatitis C virus infection

Canine distemper virus induces downregulation of GABAA,GABAB, and GAT1 expression in brain tissue of dogs

The aim of the study was to determine the expression profiles of GABA_A, GABA_B, and GAT1 using RT-PCR and the immunoreactivity of GAT1 via immunohistochemical and immunofluorescence assays in CDV-infected brain tissue of dogs. For this purpose, dogs with CDV and dogs without CDV were selected. The mRNA transcript levels of GABA_A, GABA_B, and GAT1 were significantly downregulated in brain tissue in the CDV-infected group as compared with that in non-CDV-infected brain tissue in the control group (p < 0.01, p < 0.001). In addition, the immunoreactivity of GAT1 in CDV-infected brain tissue was significantly lower than in the uninfected group (p < 0.05). We conclude that one of the main causes of myoclonus in CDV infections may be the blockage of postsynaptic inhibition in neurons or a lack of metabolism of GABA. In addition, a GABA neurotransmission imbalance could play a role in demyelination in CDV infections.

Different subtypes of GABA-A receptors are expressed in human, mouse and rat T lymphocytes

γ-aminobutyric acid (GABA) is the most prominent neuroinhibitory transmitter in the brain, where it activates neuronal GABA-A receptors (GABA-A channels) located at synapses and outside of synapses. The GABA-A receptors are primary targets of many clinically useful drugs. In recent years, GABA has been shown to act as an immunomodulatory molecule. We have examined in human, mouse and rat CD4⁺ and CD8⁺ T cells which subunit isoforms of the GABA-A channels are expressed. The channel physiology and drug specificity is dictated by the GABA-A receptor subtype, which in turn is determined by the subunit isoforms that make the channel. There were 5, 8 and 13 different GABA-A subunit isoforms identified in human, mouse and rat CD4⁺ and CD8⁺ T cells, respectively. Importantly, the γ2 subunit that imposes benzodiazepine sensitivity on the GABA-A receptors, was only detected in the mouse T cells. Immunoblots and immunocytochemistry showed abundant GABA-A channel proteins in the T cells from all three species. GABA-activated whole-cell transient and tonic currents were recorded. The currents were inhibited by picrotoxin, SR95531 and bicuculline, antagonists of GABA-A channels. Clearly, in both humans and rodents T cells, functional GABA-A channels are expressed but the subtypes vary. It is important to bear in mind the interspecies difference when selecting the appropriate animal models to study the physiological role and pharmacological properties of GABA-A channels in CD4⁺ and CD8⁺ T cells and when selecting drugs aimed at modulating the human T cells function.