Cholinergic agonists increase intracellular calcium concentration in guinea pig vestibular hair cells.
OBJECTIVE
To better understand the cholinergic receptors in vestibular hair cells (VHC) and their subtypes, and to investigate the effects of cholinergic agonists on intracellular calcium concentration ([Ca2+]i) in guinea pig VHCs.


METHODS
VHCs were isolated from guinea pig crista ampullaris by enzymatic and mechanical methods. The effect of cholinergic agonists on [Ca2+]i was examined using laser scanning confocal microscopy and the Ca2+ sensitive dye Fluo-3.


RESULTS
The results showed that the addition of acetylcholine (ACh) and carbachol (CCh), muscamic and nicotinic agonists, induced [Ca2+]i increases in all the VHCs, whereas acetylcholine bromide (ACh-Br), a nicotinic agonist, induced the [Ca2+]i increase in only a small percentage of VHCs. The ACh or CCh-induced Ca2+ response could be partially suppressed by atropine. In the presence of 0.1 mmol/L atropine, the amplitudes of ACh or CCh-induced [Ca2+]i responses became significantly smaller than those in atropine free medium (P < 0.01).


CONCLUSIONS
The results suggest the existence of cholinergic receptors in guinea pig VHCs. It is the muscamic agonists rather than nicontic receptors that dominate [Ca2+]i variation. Atropine can suppress muscamic agonist-induced Ca2+ responses.
Han
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W
Department of Otolaryngology, Head and Neck Surgery, General Hospital of PLA, Beijing 100853, China. hanweiju@bj.col.com.cn
Zhang
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S
Han
D
D
Jiang
S
S
Yang
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W
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology*; D006168:Guinea Pigs; D018069:Hair Cells, Vestibular / Q000187:drug effects* / Q000378:metabolism
D018679:Cholinergic Agonists; D001285:Atropine; D002217:Carbachol; D000109:Acetylcholine; D002118:Calcium