Neonatal seizures are associated with redistribution and loss of GABA α-subunits in the hypoxic-ischaemic pig.

Seizures are a common manifestation of hypoxic-ischaemic brain injury in the neonate. In status epilepticus models alterations to GABA R subunit expression have been suggested to contribute to (i) abnormal development of the GABAergic system, (ii) why seizures become self-sustaining and (iii) the development of pharmacoresistance. Detailed investigation of GABA R subunit protein expression after neonatal hypoxia-ischaemia (HI) is currently insufficient. Using our pig model of HI and subsequent spontaneous neonatal seizures, we investigated changes in protein expression of the three predominant α-subunits of the GABA R; α , α and α . Anaesthetized, ventilated newborn pigs (< 24 h old) were subjected to 30 min HI and subsequently recovered to 24 or 72 h. Amplitude-integrated electroencephalography was used to monitor brain activity and identify seizure activity. Brain tissue was collected post-mortem and GABA R α-subunit protein expression was analysed using western blot and immunohistochemistry. GABA R α and α protein expression was significantly reduced in animals that developed seizures after HI; HI animals that did not develop seizures did not exhibit the same reductions. Immunohistochemistry revealed decreased α and α expression, and α redistribution from the cell membrane to the cytosol, in the hippocampus of seizure animals. Multivariate analyses, controlling for HI severity and neuronal injury, revealed that seizures were independently associated with significant GABA R α reduction. This is the first study to show loss and redistribution of GABA R α-subunits in a neonatal brain experiencing seizures. Our findings are similar to those reported in models of SE and in chronic epilepsy.