Résumé
Objective To observe the effect of tetraethylplyrazine(TMP) on outward K~+ channel of outer hair cells in guinea pig cochlea.Methods 60 guinea pigs were divided into 6 groups randomly in the experiment.Auditory brainstem response was used to monitor the change of ABR thresholds and patch clamp techniques to observe the effect of TMP on outward K~+ channel.Results TMP decreased the elevated ABR threshold caused by streptomycin. The TMP increased the amplitudes of calcium sensitive potassium channels (I_ K(Ca) ) and delayed outward potassium channels (IK) of outer hair cells of guinea pig cochlea.Conclusion The study indicates that TMP may act as a protective agent against ototoxicity of streptomycin. The amplitudes of I_ K(Ca) and IK of outer hair cells are increased by the TMP,suggesting the possible mechanisms of reducing ototoxicity.
Résumé
AIM: To study the changes of K + channels of outer hair cells in guinea pig cochlea with streptomycin ototoxicity. METHODS: Auditory brainstem responses (ABR) and whole-cell patch clamp techniques were used.RESULTS: (1) The body weight of guinea pigs with streptomycin ototoxicity decreased significantly; (2) The ABR threshold markedly increased in streptomycin group (Ⅱ,Ⅲ);(3)The number of dissociated outer hair cells of guinea pigs (Ⅱ,Ⅲ) was lower than that of control (Ⅰ); (4) Streptomycin decreased the Ca 2+ -sensitive K + currents and delayed outward K + currents distinctly; (5) There was no significant difference of K + currents between Ⅰ and Ⅱ/Ⅲ. CONCLUSION: These results suggest that the inhibition of K + channels is the basis of streptomycin ototoxicity, but not the direct reason for cell death.
Résumé
AIM To analyze the mechanism of the adriamycin induced cardiomyopathy. METHODS The patch clamp technique in the whole cell recording was used to study the effect of adriamycin on L type calcium channel current( I Ca L ) in the isolated cardiomyocyte of the guinea pig. RESULTS The current voltage( I U ) curveshowed the bell shape in the control and in 0 1 mmol?L -1 adriamycin. Their peak potentials were about +10 mV. The amlitude of peak calcium current increased from (-0 93?0 05) nA to (-1 31?0 08) nA( P