RESUMO
BACKGROUND AND OBJECTIVES: It has been known that the motility of the outer hair cell controls the physiological characteristics of the organ of Corti. Motility can be divided into two different types: fast and slow motility. Slow motility can be induced by high concentration of KCl and increase of intracellular Ca2+ concentration. In this study, authors aimed to define the effect of acetylcholine, one of the efferent neurotransmitters, on the slow motility of the outer hair cells of guinea pig. MATERIALS AND METHOD: Outer hair cells were isolated from guinea pigs by enzymatic and mechanical dissociation. The length of the hair cells was recorded by CCD camera equipped on an inverted microscope. Slow motility was induced by 10 (micro)M of ionomycin and 150 mM of KCl. Carbamylcholine (1 mM), a non-hydrolyzable derivative of acetylcholine, was used to observe the effect of acetylcholine and choline chloride (1 mM) was used as control. RESULTS: The length of outer hair cell was decreased after adding 150 mM of KCl and increased after adding 10 (micro)M of ionomycin. Stimulation of carbamylcholine (1 mM) did not induce the length change of the outer hair cells. Preincubation of 1 mM of carbamylcholine also did not affect the length change induced by ionomycin or KCl in outer hair cells. CONCLUSION: We could suggest that carbamylcholine does not have an effect on the slow motility of outer hair cell induced by the change of osmotic pressure which was elicited by high potassium, or intracellular Ca2+ increase.