Potassium Channels In Utricular Type I Hair Cells

PART1 Comparative morphology of two type's hair cells from saccule and utricle under inverted phase contrast light microscopeObjective: To explore more reliable standards of vestibular hair cells of saccule and utricle from guinea pig, prepared in studies with patch clamp technique under inverted microscope, and found a more reliable base for analyzing the currents recorded in the coming research.Methods: Under inverted phase contrast light microscope, two type's hair cell's length, width and length of cilia were measured. Ratios of length, width and length of cilia were calculated and all numbers were analyzed statistically.Results: We found that width and length of cilia of two type's hair cells in saccule and utricle from guinea pig are same. Because the length of type I hair cell is longer than that of type II, against type II hair cell, the ratio between length and width is larger and the ratio of the length between cilia and cell body is smaller.Conclusions: Two type's vestibular hair cells of saccule and utricle from guinea pig may be distinguished through the ratio of cell body's length and width ,even the ratio of the length between cilia and cell body, in addition to the standards before. PART 2 Identification of K+ channels in utricular type I hair cellsObjective: To study the characteristics of currents recorded in type I utricular hair cells with different patch clamp techniques, and the channels observed to be primarily identified.Methods: Currents were recorded with whole cell recording and single channel recording in standard external solution. Both currents with different methods were analyzed and identified with TEA.Results: Whole cell currents in standard external solution have both inward part and outward rectified part. All currents disappeared with TEA, which indicated that they were potassium currents. Different results were recorded under cell attached and inside out mode with TEA, which showed they played the different mechanics in different modes. After washout TEA, currents weren't refounded in cell attached mode, while all currents recovered absolutely in inside out mode.Conclusions: Potassium channels are distributed in guinea pig type I utricular hair cells, with large conductance, and can be obstructed by TEA. The process can be reversed in inside out mode but not in cell attached mode. PART 3 Potassium currents modulated by calcium and Ach in utricular type I hair cellsObjective: To explore whether Ach or Ca can modulate the potassium currents with large conductance recorded in type I utricular hair cells. And hope to find verifications of AchR in type I utricular hair cells with patch clamp technique.Methods: Single channel recording were used to record currents from type I utricular hair cells in 3 different solutions, standard external solution, high-calcium solution, and high-calcium solution with Ach. Currents recorded in standard external solution were control. Both of three were analyzed statistically.Results: After potassium currents were recorded in standard external solution, 2.0mMCa2+ can increase both amplitude and the probability of opening of the currents. Amplitude of single channel currents increased obviously with 2.0mMCa2+ or with both 2.0mMCa2+ and 0.5mMAch in external solution. But not always, in some cells only increasing Ca2+ without Ach decreased the probability of opening (Po), which would increase obviously after 0.5mMAch were used.Conclusions: Ca2+ can stabilized membrane through increasing Amplitude of single channel currents and decreasing probability of opening (Po). 0.5mMAch can enhance the excitability of potassium channels in type I utricular hair cells, but the process need high concentration of calcium under the circumstance of unitary cell in vitro.