Issue Archive

Activation of cannabinoid CB1 receptors modulates evoked action potentials in rat retinal ganglion cells

JIANG Shu-Xia, LI Qian, WANG Xiao-Han, LI Fang, WANG Zhong-Feng^*

Institutes of Brain Science, Institute of Neurobiology and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China

Abstract

Activation of cannabinoid CB1 receptors (CB1Rs) regulates a variety of physiological functions in the vertebrate retina through modulating various types of ion channels. The aim of the present study was to investigate the effects of this receptor on cell excitability of rat retinal ganglion cells (RGCs) in retinal slices using whole-cell patch-clamp techniques. The results showed that under current-clamped condition perfusing WIN55212-2 (WIN, 5 μmol/L), a CB1R agonist, did not significantly change the spontaneous firing frequency and resting membrane potential of RGCs. In the presence of cocktail synaptic blockers, including excitatory postsynaptic receptor blockers CNQX and D-APV, and inhibitory receptor blockers bicuculline and strychnine, perfusion of WIN (5 μmol/L) hardly changed the frequencies of evoked action potentials by a series of positive current injection (from +10 to +100 pA). Phase-plane plot analysis showed that both average threshold voltage for triggering action potential and delay time to reach threshold voltage were not affected by WIN. However, WIN significantly decreased +dV/dtmax and -dV/dtmax of action potentials, suggestive of reduced rising and descending velocities of action potentials. The effects of WIN were reversed by co-application of SR141716, a CB1R selective antagonist. Moreover, WIN did not influence resting membrane potential of RGCs with synaptic inputs being blocked. These results suggest that activation of CB1Rs may regulate intrinsic excitability of rat RGCs through modulating evoked action potentials.

Key words: Action potential; cannabinoid CB1 receptor; patch-clamp; retinal ganglion cell; spontaneous firing; WIN55212-2

Received: 　　Accepted:

Corresponding author: 王中峰　　E-mail: zfwang@fudan.edu.cn

Citing This Article：

JIANG Shu-Xia, LI Qian, WANG Xiao-Han, LI Fang, WANG Zhong-Feng. Activation of cannabinoid CB1 receptors modulates evoked action potentials in rat retinal ganglion cells. Acta Physiol Sin 2013; 65 (4): 355-362 (in Chinese with English abstract).