Abstract
Objective To observe the effects of cholinergic agonists on intracellular calcium concentration (［Ca2+］i) of isolated vestibular hair cells(VHC) from the guinea pig and the effects of gentamicin on it. Methods VHCs were isolated from guinea pig crista ampullaris by enzymatic and mechanical methods. The influence of acetylcholine(ACh) and carbachol(CCh, a muscarnic and nicotinic agonist), as well as acetylcholine bromide(ACh-Br, a nicotinic agonist) on ［Ca2+］i in VHCs were examined by laser scanning confocal microscopy and the ［Ca2+］i sensitive dye Fluo-3. Results ①ACh and CCh in 0.1 or 1 mmol/L concentration induced significant increase of ［Ca2+］i in all VHCs, while ACh-Br only in 10 mmol/L concentration induced increase of ［Ca2+］i in 4/5 of VHCs. ②The ACh or CCh induced ［Ca2+］i increase was significantly suppressed by the presence of 0.1 mmol/L atropine (P<0.01). ③When 0.5 mmol/L of gentamicin was applied after 0.1 mmol/L ACh induced ［Ca2+］i increase getting to the peak, ［Ca2+］i in VHCs significantly decreased, even lower than the initial level. Conclusion The results indicated the presence of two types of cholinergic receptors on guinea pig VHCs, type M and type N. The response of ［Ca2+］i in VHCs to muscarnic agonist is significantly stronger than that to nicontic agonists. It is suggested that gentamicin can block the calcium channels of VHCs.
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