Calcium channels functional roles in the frog semicircular canal.
Different types of voltage-operated calcium channels have been described in hair cells; however, no clear functional role has been assigned to them. As a first functional characterization of vestibular calcium channels, we studied the effect of several calcium channel agonists and antagonists on whole nerve firing rate in an isolated frog semicircular canal preparation. Resting activity was affected by all dihydropyridines tested and by omegaconotoxin GVIA, whereas only nimodipine was able to reduce the mechanically evoked activity. These results indicate that nimodipine-sensitive channels play a major role in afferent transmitter release, and omega-conotoxin GVIA sensitive channels regulate the afferent firing (possibly on the postsynaptic side) but with a less important role.
Perin
P
P
Department of Physiological and Pharmacological Sciences, University of Pavia, Italy.
Soto
E
E
Vega
R
R
Botta
L
L
Masetto
S
S
Zucca
G
G
Valli
P
P
D000818:Animals; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D004095:Dihydropyridines / Q000819:agonists / Q000037:antagonists & inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005071:Evoked Potentials / Q000187:drug effects; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology; D009543:Nifedipine / Q000494:pharmacology; D009553:Nimodipine / Q000494:pharmacology; D010812:Physical Stimulation; D011893:Rana esculenta; D012665:Semicircular Canals / Q000294:innervation / Q000502:physiology*; D020867:omega-Agatoxin IVA / Q000494:pharmacology; D020960:omega-Conotoxins / Q000494:pharmacology
D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004095:Dihydropyridines; D020867:omega-Agatoxin IVA; D020960:omega-Conotoxins; D009553:Nimodipine; D009543:Nifedipine