Effects of Nifedipine and Nickel on Plateau Potentials Generated in Submucosal Interstitial Cells Distributed in the Mouse Proximal Colon.

This is the authors' abstract. We don't add key points for this paper.

The effects of nifedipine and nickel ions (Ni2+), known inhibitors of L- and T-type voltage-gated Ca-channels respectively, were investigated on plateau potentials recorded from submucosal interstitial cells distributed in the mouse proximal colon. Plateau potentials were generated at a frequency of about 15 times min(-1) and were formed of two components. The primary component had an initial fast rate of rise with a transient potential (rate of rise, 130 mV/s; peak amplitude, 35 mV) and was followed by a secondary plateau component with a sustained potential (amplitude, 25 mV; duration, 2.6 s). Each cell from which recordings were made was injected with neurobiotin. Subsequent morphological examination with a confocal microscope indicated successful visualization of injected cells only in the presence of 18beta-glycylrhetinic acid (an inhibitor of gap junctional connections), suggesting that these cells were dye-coupled with surrounding cells. The cells injected with neurobiotin exhibited an oval-shaped cell body with bipolar processes and were distributed in the submucosal layer, suggesting that they were submucosal interstitial cells of Cajal (ICC-SM). The plateau potentials were not altered by 0.01 microM nifedipine, but were reduced in duration by 0.1 microM nifedipine, and abolished by 1 microM nifedipine. The rate of rise of plateau potentials, but not their amplitude, was reduced by Ni2+ (> 10 microM), with no significant alteration of the membrane potential. In the presence of 100 microM Ni2+, the plateau potentials were changed to a triangular form. Thus, the plateau potentials were formed by two types of voltage-gated channel current: the initial component was produced by a Ni2+-sensitive channel current and the plateau component by a nifedipine-sensitive current. The possible involvement of two different types of voltage-gated Ca2+-channels in the generation of submucosal pacemaker potentials was discussed.