Electrophysiological properties of strial pericytes and the effect of aspirin on pericyte K+ channels

Abstract

The present study was designed to investigate the electrophysiological properties of strial pericytes and the effect of aspirin on pericyte K+ channels. Pericytes were identified by determining their morphological characteristics and using pericyte-associated immunofluorescence techniques. The electrophysiological properties of strial pericytes were observed with a whole-cell patch-clamp technique. Alterations in the outward current of cochlear pericytes in the stria vascularis of Guinea pigs were examined following the application of K+ channel retardants. The effects of aspirin on pericyte K+ channels were also evaluated with the whole-cell patch-clamp technique. The results demonstrated that pericytes were desmin positive, and their nuclei were large and surrounded by a small proportion of the cytoplasm. Cytoplasmic processes gradually declined in size as branches grew parallel to the capillary axis. Thus, capillaries were surrounded by tips. The electrophysiological properties of the cochlear pericytes in the stria vascularis of Guinea pigs were also determined. The membrane capacitance of the pericytes was 5.9±0.3 pF, while the membrane resistance and resting potential were 2.2±0.3 GΩ and -30.9±1.2 mV, respectively. The current densities of the pericytes (pA/pF) were 3.2±0.7, 10.6±1.0, 15.7±0.9 and 21.3±1.2 at command voltages of 0, +20, +40, and +60 mV, respectively. The K+ channels were activated when the pericytes were within the range of -20 mV to +20 mV, particularly at 0 mV. The inhibition rates of the outward current of cochlear pericytes in the stria vascularis of the Guinea pigs were determined by administering iberiotoxin (IBTX) and IBTX + 4-aminopyridine. Once the background leakage current was removed, the following inhibition rates were obtained with 3, 10, 30, 300 and 1,000 μmol/l aspirin: 20.8±4.8, 34.1±6.9, 48.2±6.7, 63.6±7.1 and 65.7±8.1%, respectively. The outward current of the cochlear pericytes in the stria vascularis was inhibited by aspirin with a half maximal inhibitory concentration of 24.5±4.5 μmol/l. The membranes of the pericytes in the stria vascularis are characterized by high-conductance calcium-activated K+ (BKCa) and voltage-dependent K+ (KV) channels. The outward current of the cochlear pericytes in the stria vascularis of Guinea pigs was inhibited by aspirin in a concentration-dependent manner. In addition, BKCa and KV channels were inhibited by aspirin.