Network-Driven Activity and Neuronal Excitability in Hippocampus of Neonatal Rats with Prenatal Hyperhomocysteinemia
Maternal hyperhomocysteinemia (HHCy) correlated with a number of complications such as abruption placentae, preeclampsia syndrome, in utero fetal death and fetal neural tube defects, cognitive impairment, and neurodegeneration during postnatal development. In the present study, we investigated the effects of prenatal HHCy on electrophysiological features and spontaneous network activity of neurons in hippocampus of rats of the first postnatal week. The analysis of intrinsic electrophysiological properties of pyramidal neurons has shown the decrease of the membrane capacitance and the threshold of generation of action potentials in rats with prenatal HHCy without alteration of the input resistance and resting membrane potential. In trains of action potentials elicited with prolonged current injections, an increase of interspike intervals and a broadening of action potentials during repetitive firing were observed in control neurons. In the neurons of pups with prenatal HHCy, the changes in interspike intervals were not significant and the broadening of action potentials in train was less pronounced. Using extracellular field potential recordings from the hippocampal slices, we found that the network activity in hippocampal slices from rats with prenatal HHCy displayed several abnormalities including the increase in overall neuronal firing and reduction of frequency of giant depolarizing potentials in CA3 regions. We conclude that the increased neuronal excitability and impairment of network activity in hippocampus can underlie neurodevelopmental abnormalities and hyperexcitability in prenatal HHCy.
KeywordsMaternal hyperhomocysteinemia Hippocampus Giant depolarizing potentials Neuronal excitability
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