Maternal hyperhomocysteinemia increases seizures susceptibility of neonatal rats

Aims: Neonatal seizures are severe pathologies which may result in long-term neurological consequences. High plasma concentrations of homocysteine - hyperhomocysteinemia (hHCy) - are associated with epilepsy. In the present study, we evaluated susceptibility to seizure of neonatal rats with prenatal hHCy.Main methods: Prenatal hHCy was induced by feeding females with a high-methionine diet. Experiments were performed on pups during the first three postnatal weeks. Flurothyl-induced epileptic behavior was assessed according to Racine's scale. Epileptiform activity in the hippocampus was recorded using electrophysiological methods. The balance of excitation/inhibition, functional GABAergic inhibition and GABA reversal potential in hippocampal neurons were analyzed.Key findings: Rats with hHCy developed more severe stages of behavioral patterns during flurothyl-induced epilepsy with shorter latency. Electrophysiological recordings demonstrated higher background neuronal activity in rats with hHCy. Seizure-like events triggered by flurothyl (in vivo) or 4-aminopyridine (in vitro) showed shorter latency, higher power and amplitude. An increased glutamate/GABA synaptic ratio was shown in the pyramidal neurons of rats with hHCy and more slices demonstrated excitation by isoguvacine, a selective GABA(A) receptor agonist, during the first and second postnatal weeks. The GABA driving force and the reversal potential of GABA (A) currents were more positive during the second postnatal week for hHCy rats.Significance: The higher susceptibility to seizures in rats with prenatal hHCy due to a shift in the balance of excitation/inhibition toward excitation may underlie the clinical evidence about the association of hHCy with an increased risk of epilepsy.

Automated summary

In this study, we induced prenatal hyperhomocysteinemia (hHCy) in rats by feeding females with a high-methionine diet and evaluated the susceptibility to seizures in neonatal rats. The results showed that rats with hHCy exhibited more severe stages of behavior and shorter latency during flurothyl-induced epilepsy, and had higher neuronal activity. These findings suggest that the increased risk of epilepsy associated with hHCy may be due to a shift in the balance of excitation/inhibition towards excitation.