L- and N-type Ca2+ channels in adult rat carotid body chemoreceptor type I cells.
1. Whole-cell voltage-dependent Ca2+ currents recorded from chemoreceptor type I cells of the adult rat carotid body had maximum amplitudes of -94 pA in 10 mM Ca2+ and were half-inactivated at a holding potential of -38 mV. Somatostatin and dopamine inhibited whole-cell Ca2+ current in type I cells. 2. The dihydropyridine agonist (+)202-791 increased the Ca2+ current amplitude by 106% at a step potential of -18 mV. The dihydropyridine antagonist nimodipine decreased the Ca2+ current amplitude by 40% from a holding potential of -80 mV, and by 74% from a holding potential of -60 mV. The nimodipine-sensitive current had a maximum amplitude at a membrane potential of -12 mV. omega-Conotoxin GVIA (omega-CgTX GVIA) blocked the whole-cell Ca2+ current by 40%. The omega-CgTX GVIA-sensitive current had a maximum amplitude at a membrane potential of +2 mV. 3. In summary, type I cells of the adult rat carotid body have dihydropyridine-sensitive L-type and omega-conotoxin GVIA-sensitive N-type voltage-dependent Ca2+ channels. These channels may play a role in the voltage-gated entry of Ca2+ necessary for stimulus-secretion coupling in response to changes in arterial PO2, PCO2 and pH. Inhibition of the Ca2+ currents by somatostatin and dopamine may alter the chemotransduction signal in type I cells.
e Silva
M J
MJ
Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta 30912-2300, USA.
Lewis
D L
DL
D000818:Animals; D001464:Barium / Q000378:metabolism; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D002344:Carotid Body / Q000166:cytology / Q000378:metabolism*; D004298:Dopamine / Q000494:pharmacology; D004594:Electrophysiology; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D009553:Nimodipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013004:Somatostatin / Q000494:pharmacology; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D020866:omega-Conotoxin GVIA; D020960:omega-Conotoxins
D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D010455:Peptides; D020960:omega-Conotoxins; C075851:omega-conotoxin-MVIIC; D001464:Barium; D013004:Somatostatin; D009553:Nimodipine; D020866:omega-Conotoxin GVIA; D014446:Tyrosine 3-Monooxygenase; D004298:Dopamine