Modulation of spontaneous Ca2+-activated Cl- currents in the rabbit corpus cavernosum by the nitric oxide-cGMP pathway.
The whole-cell perforated patch clamp technique was used to study membrane currents in isolated rabbit corpus cavernosum smooth muscle cells. Depolarization from -80 mV to the range -40 to -10 mV evoked a nifedipine-sensitive Ca(2+) current that was followed by a slower inward current that activated over several hundred milliseconds. The slow current reversed near the Cl(-) equilibrium potential (E(Cl)) and was reduced by anthracene-9-carboxylic acid (A9C; 1 mm) and niflumic acid (100 microm), suggesting that it was a Ca(2+)-activated Cl(-) current. When held constantly at -60 mV, over 70% of cells fired spontaneous transient inward currents (STICs), the amplitudes of which were reduced by A9C and niflumic acid. STICs reversed near E(Cl) in a symmetrical Cl(-) gradient and when [Cl(-)](o) was substituted with glutamate or I(-), the reversal potential shifted to more positive or more negative values, respectively, confirming that STICs were mediated by Cl(-) channels. STICS were also blocked by cyclopiazonic acid, 2-aminoethoxydiphenyl borate (2-APB) and 2-nitro-4-carboxyl-N,N-diphenylcarbamate (NCDC), suggesting that they depended on IP(3)-mediated Ca(2+)-release from the sarcoplasmic reticulum. Modulation by the NO-cGMP pathway was investigated by applying nitrosocysteine, 3-(5-hydroxymethyl-2-furyl)-1-benzyl indazole (YC-1), and 8-bromo cGMP, all three of which abolished STIC activity. YC-1 also reduced noradrenaline-evoked inward currents, but had no effect on similar currents evoked by caffeine, suggesting that cGMP selectively inhibited IP(3)-mediated Ca(2+) release. We propose that Ca(2+)-activated Cl(-) currents underlie detumescent tone in the corpus cavernosum, and that modulation of this mechanism by the NO-cGMP pathway is important during penile erection.
Craven
M
M
Smooth Muscle Group, Department of Physiology, The Queen's University of Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK.
Sergeant
G P
GP
Hollywood
M A
MA
McHale
N G
NG
Thornbury
K D
KD
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010410:Penile Erection / Q000502:physiology; D010413:Penis / Q000502:physiology*; D011817:Rabbits; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D002712:Chlorides; D004791:Enzyme Inhibitors; D007211:Indoles; D020030:Nitric Oxide Donors; D014662:Vasoconstrictor Agents; D009569:Nitric Oxide; D006152:Cyclic GMP; D002118:Calcium; D009638:Norepinephrine; C000543:cyclopiazonic acid