Cannabinoid receptor-mediated inhibition of calcium signaling inrat retinal ganglion cells

[摘要] Purpose: The physiological actions of CB1 cannabinoidreceptors (CB1Rs) in mammalian retina have yet to be fullydescribed in all cell types. Here we investigate the actions ofCB1R activation on high-voltage-activated (HVA) Ca2+ channelcurrents in purified cultures of rat retinal ganglion cells (RGCs).Methods: Reverse transcriptase polymerase chain reaction (RT-PCR)and immunocytochemistry were used to determine the presence ofCB1R mRNA and protein in a purified RGC culture generated fromneonatal rats using a two-step panning procedure. Ruptured-patchwhole-cell voltage clamp was used to test the effect of CB1Ragonists (WIN 55,212-2) and antagonists (SR141716A, AM281) on HVACa2+ channel currents.Results: RT-PCR analysis confirmed CB1R mRNA in cultured RGCsand immunocytochemistry for CB1R protein revealed labeling in boththe cell body and neurites of isolated RGCs. Patch-clamp recording fromcultured rat RGCs showed that the CB1R agonist WIN 55,212-2inhibited HVA Ca2+ channel currents up to 50% in aconcentration-dependent manner (0.5, 1, and 5 μM). The Ca2+channel current inhibition by WIN 55,212-2 was blocked by CB1Rantagonists AM281 and SR141716.Conclusions: Activation of CB1Rs in cultured RGCs inhibits HVACa2+ channel currents. These data show that cannabinoids canmodify the excitability of RGCs and could affect retinal output. Thisfinding has implications for retinal signal processing as it suggeststhat endogenous cannabinoids have inhibitory effects on RGCs and thatexogenous cannabinoids could modulate retinal function by this pathwayas well.

[学科分类] 生物化学/生物物理