[Effects of neuroactive substances on intracellular free Ca2+ concentration in isolated outer hair cells of the guinea pig cochlea].
OBJECTIVE
To measure the effects of neuro-active substances on intracellular free Ca2+ concentration ([Ca2+]i) in isolated outer hair cells(OHCs) of the guinea pig cochlea.


METHODS
The fura-2 microfluorimetry was used to measure changes of [Ca2+]i in OHCs of the guinea pig cochlea after application of acetylcholine, ATP and carbacholine.


RESULTS
Acetylcholine, ATP and carbacholine increased [Ca2+]i (acetylcholine: 0.74 +/- 0.12 mumol/L, ATP: 0.65 +/- 0.11 mumol/L, carbacholine: 1.16 +/- 0.27 mumol/L) in OHCs in the presence of extracellular Ca2+. In the absence of extracellular Ca2+, however, only ATP induced a gradual and small [Ca2+]i elevation, whereas other substances did not.


CONCLUSIONS
Acetylcholine and carbacholine, the cholinergic mascarinic agonists, increased [Ca2+]i in OHCs by acting at receptor-induced ion channel resulting in Ca2+ efflux. ATP-induced elevation of [Ca2+]i without Ca2+ in extracellular medium is due to a release of Ca2+ from an intracellular reservoir.
Yang
J
J
Union Hospital, Tongji Medical University, Wuhan 430022.
Wang
J
J
Wei
S
S
D000109:Acetylcholine / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002478:Cells, Cultured; D005260:Female; D006168:Guinea Pigs; D018072:Hair Cells, Auditory, Outer / Q000166:cytology / Q000378:metabolism*; D008297:Male
D000255:Adenosine Triphosphate; D002217:Carbachol; D000109:Acetylcholine; D002118:Calcium