Large-conductance calcium-activated potassium channels in neonatal rat intracardiac ganglion neurons.
The properties of single Ca2+-activated K+ (BK) channels in neonatal rat intracardiac neurons were investigated using the patch-clamp recording technique. In symmetrical 140 mM K+, the single-channel slope conductance was linear in the voltage range -60/+60 mV, and was 207+/-19 pS. Na+ ions were not measurably permeant through the open channel. Channel activity increased with the cytoplasmic free Ca2+ concentration ([Ca2+]i) with a Hill plot giving a half-saturating [Ca2+] (K0.5) of 1.35 microM and slope of approximately equals 3. The BK channel was inhibited reversibly by external tetraethylammonium (TEA) ions, charybdotoxin, and quinine and was resistant to block by 4-aminopyridine and apamin. Ionomycin (1-10 microM) increased BK channel activity in the cell-attached recording configuration. The resting activity was consistent with a [Ca2+]i <100 nM and the increased channel activity evoked by ionomycin was consistent with a rise in [Ca2+]i to > or =0.3 microM. TEA (0.2-1 mM) increased the action potential duration approximately equals 1.5-fold and reduced the amplitude and duration of the afterhyperpolarization (AHP) by 26%. Charybdotoxin (100 nM) did not significantly alter the action potential duration or AHP amplitude but reduced the AHP duration by approximately equals 40%. Taken together, these data indicate that BK channel activation contributes to the action potential and AHP duration in rat intracardiac neurons.
Franciolini
F
F
Dipartmento Biologia Cellulare e Molecolare, Universita' di Perugia, Italy.
Hogg
R
R
Catacuzzeno
L
L
Petris
A
A
Trequattrini
C
C
Adams
D J
DJ
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D018999:Charybdotoxin / Q000494:pharmacology; D004553:Electric Conductivity; D005726:Ganglia, Parasympathetic / Q000166:cytology*; D006321:Heart / Q000294:innervation; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D007700:Kinetics; D051036:Large-Conductance Calcium-Activated Potassium Channels; D009125:Muscle Relaxants, Central / Q000494:pharmacology; D009474:Neurons / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000502:physiology*; D024681:Potassium Channels, Calcium-Activated; D011803:Quinine / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000378:metabolism; D019789:Tetraethylammonium / Q000494:pharmacology
D007476:Ionophores; D051036:Large-Conductance Calcium-Activated Potassium Channels; D009125:Muscle Relaxants, Central; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D018999:Charybdotoxin; D015759:Ionomycin; D019789:Tetraethylammonium; D012964:Sodium; D011803:Quinine; D011188:Potassium; D002118:Calcium