Abstract
Purpose: :
Sigma-1 receptor (s1r) activation provides neuroprotective effects in retinal ganglion cells (RGCs) in both in vivo and in vitro studies. The purpose of this study is to determine the role s1rs play in controlling calcium dynamics through activated NMDA receptors in primary RGCs. Additionally, this study aims to identify cell survival/apoptotic pathways that are activated through the prolonged stimulation of NMDA receptors, and assess the potential role that s1r plays in regulating those pathways.
Methods: :
Purification and culture of RGCs were performed by sequential immunopanning using Thy 1 antibody from P3-P7 Sprague-Dawley rats. Calcium imaging was used to measure the intracellular changes in calcium when subjecting these cells to 100uM of NMDA. Western blots were also performed to determine signaling pathways that may be linked to NMDA induced cell survival or excitotoxicity.
Results: :
Calcium imaging results have shown that s1r ligands, (+)-N-allylnormetazocine hydrochloride [(+)-SKF10047] and Pentazocine, in primary RGCs inhibited the influx of calcium through NMDA receptors in a dose dependent manner. Also, 100uM treatment of NMDA on primary RGCs caused a greater than 2 fold induction of the transcription factor cAMP-responsive element binding protein (pCREB) following 6 hrs of treatment.
Conclusions: :
S1r agonist pre-treatment decreased the levels of calcium influx through NMDA receptors. Additionally, pCREB is elevated following NMDA treatment. Since pCREB is considered an important signaling molecule implicated in cell survival and synaptic plasticity, further studies are needed to investigate the potential link that NMDA signaling plays in the survival of RGCs and if s1r impacts NMDA induced pCREB expression.
Keywords: neuroprotection • calcium • receptors