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Open Access Research article

Calcium sparks in the intact gerbil spiral modiolar artery

Gayathri Krishnamoorthy1, Keil Regehr13, Samantha Berge1, Elias Q Scherer2 and Philine Wangemann1*

Author Affiliations

1 Anatomy & Physiology Department, Kansas State University, Manhattan, Kansas 66506, USA

2 ENT-Department, Technical University of Munich, Munich, Germany

3 Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA

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BMC Physiology 2011, 11:15  doi:10.1186/1472-6793-11-15

Published: 26 August 2011

Abstract

Background

Calcium sparks are ryanodine receptor mediated transient calcium signals that have been shown to hyperpolarize the membrane potential by activating large conductance calcium activated potassium (BK) channels in vascular smooth muscle cells. Along with voltage-dependent calcium channels, they form a signaling unit that has a vasodilatory influence on vascular diameter and regulation of myogenic tone. The existence and role of calcium sparks has hitherto been unexplored in the spiral modiolar artery, the end artery that controls blood flow to the cochlea. The goal of the present study was to determine the presence and properties of calcium sparks in the intact gerbil spiral modiolar artery.

Results

Calcium sparks were recorded from smooth muscle cells of intact arteries loaded with fluo-4 AM. Calcium sparks occurred with a frequency of 2.6 Hz, a rise time of 17 ms and a time to half-decay of 20 ms. Ryanodine reduced spark frequency within 3 min from 2.6 to 0.6 Hz. Caffeine (1 mM) increased spark frequency from 2.3 to 3.3 Hz and prolonged rise and half-decay times from 17 to 19 ms and from 20 to 23 ms, respectively. Elevation of potassium (3.6 to 37.5 mM), presumably via depolarization, increased spark frequency from 2.4 to 3.2 Hz. Neither ryanodine nor depolarization changed rise or decay times.

Conclusions

This is the first characterization of calcium sparks in smooth muscle cells of the spiral modiolar artery. The results suggest that calcium sparks may regulate the diameter of the spiral modiolar artery and cochlear blood flow.