Plasticity at axon initial segment of hippocampal CA3 neurons in rat after status epilepticus induced by lithium-pilocarpine.

ABSTRACT

BACKGROUND: The axon initial segment (AIS) is a specialized membrane region in the axon of neurons wherein numerous specific voltage-gated sodium channels (VGSCs) are clustered and action potentials are initiated. The AIS is currently considered as a new plastic hotspot. METHODS: We investigated the alterations in Nav1.6 (SCN8A) and its adapter protein ankyrin G in the AIS of the hippocampal cornu ammonis 3 (CA3) pyramidal cells of rat after status epilepticus induced by lithium-pilocarpine (PISE). RESULTS: Nav1.6 and ankyrin G were colocalized in the AIS of hippocampal CA3 pyramidal neurons. Compared with the control group, the protein and mRNA expression of Nav1.6 increased within 24 h and 60 days after PISE. By contrast, ankyrin G protein expression decreased slightly within 24 h but increased within 60 days, whereas ankyrin G mRNA increased within 24 h and 60 days after PISE. However, the protein and mRNA expression levels of Nav1.6 and ankyrin G within 7 days after PISE did not differ significantly with those of the control. CONCLUSIONS: Nav1.6 and ankyrin G may participate in the plastic changes in the AIS of hippocampus CA3 neurons after PISE and play potential roles in epileptogenesis by regulating neuronal excitability.