Content area
Full text
Acta Neurochir (2013) 155:23732380 DOI 10.1007/s00701-013-1836-4
CLINICAL ARTICLE - FUNCTIONAL
Plasticity at axon initial segment of hippocampal CA3 neurons in rat after status epilepticus induced by lithiumpilocarpine
Li Feng & Ai-Ping Li & Mei-Ping Wang & Dan-Ni Sun &
Ye-Lan Wang & Li-Li Long & Bo Xiao
Received: 16 January 2013 /Accepted: 29 July 2013 /Published online: 14 August 2013 # Springer-Verlag Wien 2013
AbstractBackground 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.
Keywords Voltage-gatedsodiumchannel .AnkyrinG .Axon initial segment . Epilepsy
Introduction
The axon initial segment (AIS) is classically defined as the unmyelinated region situated in the proximal axon of neurons [26]. The AIS membrane is rich in voltage-gated ion channels, cytoskeletal adaptor proteins and cell adhesion molecules (CAMs), and all of them are accurately assembled [10]. Considering its special molecular organization, the AIS has unique electrical properties, such as inducing action potentials within neurons and regulating the integration of synaptic inputs, intrinsic excitability, and transmitter release [6, 16, 27, 34, 35]. In addition, the distribution of Nav channel subtypes in the AIS is polarized. Hu et al. [13] suggested that the dense clusters of Nav1.6 channels at...