Decreased GABAA receptors functional regulation in the cerebral cortex and brainstem of hypoxic neonatal rats: effect of glucose and oxygen supplementation

Abstract

Hypoxia in neonates can lead to biochemical and molecular alterations mediated through changes in neurotransmitters resulting in permanent damage to brain. In this study, we evaluated the changes in the receptor status of GABA(A) in the cerebral cortex and brainstem of hypoxic neonatal rats and hypoxic rats supplemented with glucose and oxygen using binding assays and gene expression of GABA(Aalpha1) and GABA(Agamma5). In the cerebral cortex and brainstem of hypoxic neonatal rats, a significant decrease in GABA(A) receptors was observed, which accounts for the respiratory inhibition. Hypoxic rats supplemented with glucose alone and with glucose and oxygen showed a reversal of the GABA(A) receptors, andGABA(Aalpha1) and GABA(Agamma5) gene expression to control. Glucose acts as an immediate energy source thereby reducing the ATP-depletion-induced increase in GABA and oxygenation, which helps in encountering anoxia. Resuscitation with oxygen alone was less effective in reversing the receptor alterations. Thus, the results of this study suggest that reduction in the GABA(A) receptors functional regulation during hypoxia plays an important role in mediating the brain damage. Glucose alone and glucose and oxygen supplementation to hypoxic neonatal rats helps in protecting the brain from severe hypoxic damage.

Fig. 1

Binding parameters of [³H] bicuculline against bicuculline in the cerebral cortex of experimental neonatal rats

Fig. 2

Binding parameters of [³H] bicuculline against bicuculline in the brain stem of experimental neonatal rats

Fig. 3

Real Time amplification of GABA (A)α₁ receptor mRNA from the Cerebral cortex of control and experimental neonatal rats. Note: Values are mean ± SD of 4–6 separate experiments. Each group consist of 6–8 rats. ^a P < 0.05 when compared to control, ^c P < 0.05 when compared to hypoxic group

Fig. 4

Real-Time amplification of GABA (A)γ₅ receptor mRNA from the Cerebral cortex of control and experimental neonatal rats. Note: Values are mean ± SD of 4–6 separate experiments. Each group consists of 6–8 rats. ^a P < 0.05 when compared to control, ^c P < 0.05 when compared to hypoxic group

Fig. 5

Real Time amplification of GABA (A)α₁ receptor mRNA from the brain stem of control and experimental neonatal rats. Note: Values are mean ± SD of 4–6 separate experiments. Each group consists of 6–8 rats. ^a P < 0.05 when compared to control, ^c P < 0.05 when compared to hypoxic group

Fig. 6

Real-Time amplification of GABA (A)γ₅ receptor mRNA from the Brain stem of control and experimental neonatal rats. Note: Values are mean ± SD of 4–6 separate experiments. Each group consists of 6–8 rats. ^b P < 0.001 when compared to control, ^d P < 0.001 when compared to hypoxic group