Differential effect of transient global ischaemia on the levels of γ‐aminobutyric acid type A (GABAA) receptor subunit mRNAs in young and older rats

Abstract

This study has investigated how global brain ischaemia/reperfusion (I/R) modifies levels of mRNAs encoding γ-aminobutyric acid type A (GABA(A)) receptor α1, β2 and γ2 subunits and glutamic acid decarboxylase 65 (GAD65) in an age- and structure-dependent manner. Gene expression in response to treatment with the anti-inflammatory agent meloxicam was also investigated. Global ischaemia was induced in 3- and 18-month-old male Sprague-Dawley rats. CA1, CA3, and dentate gyrus (DG) hippocampal areas, cerebral cortex (CC) and caudate putamen (C-Pu) from sham-operated and I/R-injured animals were excised 48 h after the insult and prepared for quantitative polymerase chain reaction assays. Following I/R, meloxicam treatment was also carried out on young animals. Data revealed significant decreases in the levels of all GABA(A) receptor subunit transcripts in the hippocampus of both young and older injured animals compared with sham-operated ones. In contrast, there was either an increase or no change in GAD65 mRNA levels. GABA(A) receptor subunit transcript decreases were also observed in the CC and C-Pu in young injured animals but not in the CC of the older injured ones; interestingly, significant increases were observed in the C-Pu of older injured animals compared with controls. Meloxicam treatment following the insult resulted in a diminution of the previously described I/R response. The data indicate that I/R results in the modification of the levels of several gene transcripts involved in GABAergic signalling in both the pre- and postsynaptic components, of this neurotransmitter system, in an age- and structure-dependent manner.