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Eye CNG channel is modulated by nicotine
J E McGeoch1, M W McGeoch, G Guidotti
1Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
Biochemical and Biophysical Research Communications
|September 25, 1995
Abstract:
The cyclic-nucleotide gated channel (CNG channel) of the rod outer segment of the retina (ROS) has its closed conformation stabilized by nicotine. Calcium and cGMP influence the Ki of the channel current to nicotine. Calcium lowers the Ki and cGMP increases it, giving a range of Ki between 10(-11) and 10(-8) M.
Insights
Nicotine stabilizes the closed state of retinal cyclic-nucleotide gated (CNG) channels. Calcium and cGMP modulate nicotine
Area of Science:
- Biophysics
- Neuroscience
- Molecular Biology
Background:
- The cyclic-nucleotide gated (CNG) channel in retinal rod outer segments (ROS) is crucial for visual signal transduction.
- Understanding the regulation of CNG channel gating is essential for comprehending photoreceptor function.
Purpose of the Study:
- To investigate the effect of nicotine on the closed conformation of the ROS CNG channel.
- To determine how calcium and cyclic guanosine monophosphate (cGMP) influence the channel's affinity for nicotine.
Main Methods:
- Electrophysiological recordings were used to measure channel currents.
- The inhibition constant (Ki) for nicotine was determined under varying calcium and cGMP concentrations.
Main Results:
- Nicotine was found to stabilize the closed state of the ROS CNG channel.
- Calcium ions decreased the Ki for nicotine, indicating increased affinity.
- cGMP increased the Ki for nicotine, suggesting decreased affinity.
- The Ki for nicotine ranged from 10^-11 to 10^-8 M.
Conclusions:
- Nicotine acts as a stabilizer of the closed state of the retinal CNG channel.
- The affinity of the CNG channel for nicotine is modulated by intracellular calcium and cGMP levels.
- These findings provide insights into the complex allosteric regulation of CNG channels in photoreceptors.