Role of A-type K+ channels in spike broadening observed in soma and axon of Hermissenda type-B photoreceptors: a simulation study.
In Hermissenda type-B photoreceptors, the spike is generated in the axon and back-propagated to the soma, resulting in smaller somatic spikes. Experimentally, blocking the A-type K+ current (IK,A) results in broadening of somatic spikes. Similarly, in a compartmental model of the photoreceptor, reducing the maximum A-type K+ conductance (gK,Amax) results in broadening of somatic spikes. However, simulations predict that little or no broadening of axonal spikes occurs when gK,Amax is reduced. The results can be explained by the voltage-dependent properties of IK,A and the different potential ranges that the somatic and axonal spike traverse. Because of the steeper I-V curve and faster activation of the K+ channels at higher potentials, the recruitment of additional K+ channels in the axon is able to compensate for the decrease in K+ conductance, yielding less spike broadening. These results also support the idea that spike duration in the axon may not be reliably inferred based upon recordings collected from the soma.
Cai
Yidao
Y
Department of Neurobiology and Anatomy, The University of Texas at Houston Medical School, 6431 Fannin Street, Houston, Texas 77030, USA. yidao.cai@gmail.com
Flynn
Mark
M
Baxter
Douglas A
DA
Crow
Terry
T
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D001369:Axons / Q000502:physiology* / Q000528:radiation effects; D003198:Computer Simulation; D004558:Electric Stimulation / Q000379:methods; D049870:Hermissenda / Q000166:cytology / Q000502:physiology; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000502:physiology*; D008959:Models, Neurological; D009431:Neural Conduction / Q000502:physiology; D017956:Photoreceptor Cells, Invertebrate / Q000166:cytology / Q000502:physiology*; D013997:Time Factors
D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits