NR1 Knockdown Reveals CA1 Injuryduring a Developmental Period of High Seizure Susceptibility Despite Reduced Seizure Activity

Abstract

NMDA receptors (NMDARs) are important for the propagation of seizures. To understand the role of NR1 subunits in the propagation of seizures we knocked down the NR1 subunit by intracranial injection of antisense deoxyoligonucleotides (NR1-AS-ODNs) into the right hippocampus during a window of maximal seizure susceptibility in development. Control missense and sense ODNs followed by focal injection of NMDA (2.5-25 nmoles) into the hippocampal CA1 and sensorimotor cortex of P15 rat pups resulted in behavioral and electrographic (EEG) seizures. After NR1 knockdown, low- and high-doses produced little or no spike activity in the hippocampus and overlying sensorimotor cortex as predicted. Despite reduced activity in the hippocampal and cortical EEG, intracranial NMDA or peripheral kainate (KA)-induced seizures led to paradoxical cell death of CA1 neurons, which is not typically observed in this age group. Histological changes were modest or absent in the cortex away from the infusion site. Signal specificity of the targeted CA1 or cortex was observed in autoradiograms, immunohistochemistry and Western blots. After knockdown, Ca2+ influx was suppressed as both NMDA and muscimol-stimulated Ca2+ permeability of the immature CA1 was blocked in ex-vivo slices measured with FURA-2AM optical dye imaging. Data suggest that certain constituent levels of NMDA receptors distributed on excitatory and/or inhibitory interneurons may be developmentally required for survival of CA1 pyramidal neurons during a critical period when ictal activity is present. Moreover, selective NR1 subunit downregulation simultaneously reduces NMDA and GABA A receptor Ca2+ ion permeability properties that may contribute to a premature cell death mechanism.

Alpha-1A adrenergic receptor activation increases inhibitory tone in CA1 hippocampus

“…Indeed, the structure is implicated in a majority of temporal lobe epilepsies (McNamara, 1994). CA1 hippocampus is particularly vulnerable to neuronal damage following seizure activity (Freund et al, 1991; Cavazos et al, 1994; Kaur et al, 2007), which can have dire consequences as this region is heavily implicated in synaptic plasticity associated with learning and episodic memory (for review see Neves et al, 2008). A strategy to decrease hyperexcitability in the hippocampus, with attention to CA1, might therefore prove important in the treatment of temporal lobe epilepsies.…”

Modification of glutamatergic mechanisms in the model of posttraumatic stress disorder

“…Установлено, что GluN1 как обязательная субъединица играет главную роль в функционировании NMDA-рецепторов [12]. Полагают, что именно она важна для формирования адаптивных реакций организма [14][15][16][17] и развития патологии нервной системы при стрессовых воздействиях [17,18].…”