| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557
Spontaneous transient outward currents
(STOCs) were recorded from smooth muscle cells of the
guinea pig taenia coli using the whole cell patch-clamp technique.
STOCs were resolved at potentials positive to 
50 mV. Treating
cells with caffeine (1 mM) caused a burst of outward currents
followed by inhibition of STOCs. Replacing extracellular
Ca2+ with equimolar
Mn2+ caused STOCs to "run
down." Iberiotoxin (200 nM) or charybdotoxin (ChTX; 200 nM)
inhibited large-amplitude STOCs, but small-amplitude "mini-STOCs"
remained in the presence of these drugs. Mini-STOCs were reduced by
apamin (500 nM), an inhibitor of small-conductance Ca2+-activated
K+ channels (SK channels).
Application of ATP or 2-methylthioadenosine 5'-triphosphate
(2-MeS-ATP) increased the frequency of STOCs. The effects of 2-MeS-ATP
persisted in the presence of charybdotoxin but were blocked by
combination of ChTX (200 nM) and apamin (500 nM). 2-MeS-ATP did not
increase STOCs in the presence of pyridoxal phosphate
6-azophenyl-2',4'-disulfonic acid, a
P2 receptor blocker. Similarly,
pretreatment of cells with U-73122 (1 µM), an inhibitor of
phospholipase C (PLC), abolished the effects of 2-MeS-ATP. Xestospongin
C, an inositol 1,4,5-trisphosphate
(IP3) receptor blocker,
attenuated STOCs, but these events were not affected by ryanodine. The
data suggest that purinergic activation through P2Y receptors results in localized
Ca2+ release via PLC- and
IP3-dependent mechanisms. Release
of Ca2+ is coupled to STOCs, which
are composed of currents mediated by large-conductance
Ca2+-activated
K+ channels and SK channels. The
latter are thought to mediate hyperpolarization and relaxation
responses of gastrointestinal muscles to inhibitory purinergic stimulation.
calcium sparks; small-conductance calcium-activated potassium channels; purinergic neurotransmission; P2Y receptors; inositol 1,4,5-trisphosphate receptors
This article has been cited by other articles:
|
|
 |
|
  M. Kim, G. W. Hennig, K. Park, I. S. Han, T. K. Smith, S. D. Koh, and B. A. Perrino Modulation of murine gastric antrum smooth muscle STOC activity and excitability by phospholamban J. Physiol., October 15, 2008; 586(20): 4977 - 4991. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. F. King and A. Townsend-Nicholson Involvement of P2Y1 and P2Y11 Purinoceptors in Parasympathetic Inhibition of Colonic Smooth Muscle J. Pharmacol. Exp. Ther., March 1, 2008; 324(3): 1055 - 1063. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. J. Hwang, N. O'Kane, C. Singer, S. M. Ward, K. M. Sanders, and S. D. Koh Block of inhibitory junction potentials and TREK-1 channels in murine colon by Ca2+ store-active drugs J. Physiol., February 15, 2008; 586(4): 1169 - 1184. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Kim, G. W. Hennig, T. K. Smith, and B. A. Perrino Phospholamban knockout increases CaM kinase II activity and intracellular Ca2+ wave activity and alters contractile responses of murine gastric antrum Am J Physiol Cell Physiol, February 1, 2008; 294(2): C432 - C441. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G.-D. Wang, X.-Y. Wang, H.-Z. Hu, S. Liu, N. Gao, X. Fang, Y. Xia, and J. D. Wood Inhibitory neuromuscular transmission mediated by the P2Y1 purinergic receptor in guinea pig small intestine Am J Physiol Gastrointest Liver Physiol, June 1, 2007; 292(6): G1483 - G1489. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. P. Monaghan, S. D. Koh, S. Ro, J. Yeom, B. Horowitz, and K. M. Sanders Nucleotide regulation of the voltage-dependent nonselective cation conductance in murine colonic myocytes Am J Physiol Cell Physiol, November 1, 2006; 291(5): C985 - C994. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. M. Hagen, O. Bayguinov, and K. M. Sanders VIP and PACAP regulate localized Ca2+ transients via cAMP-dependent mechanism Am J Physiol Cell Physiol, August 1, 2006; 291(2): C375 - C385. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. B. Bolton Calcium events in smooth muscles and their interstitial cells; physiological roles of sparks J. Physiol., January 1, 2006; 570(1): 5 - 11. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. M. Hagen, O. Bayguinov, and K. M. Sanders {beta}1-Subunits are required for regulation of coupling between Ca2+ transients and Ca2+-activated K+ (BK) channels by protein kinase C Am J Physiol Cell Physiol, November 1, 2003; 285(5): C1270 - C1280. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. H. Clarson, V. H. J. Roberts, S. L. Greenwood, and A. C. Elliott ATP-stimulated Ca2+-activated K+ efflux pathway and differentiation of human placental cytotrophoblast cells Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2002; 282(4): R1077 - R1085. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
O. Bayguinov, B. Hagen, J. L. Kenyon, and K. M. Sanders Coupling strength between localized Ca2+ transients and K+ channels is regulated by protein kinase C Am J Physiol Cell Physiol, November 1, 2001; 281(5): C1512 - C1523. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Ro, W. J. Hatton, S. D. Koh, and B. Horowitz Molecular properties of small-conductance Ca2+-activated K+ channels expressed in murine colonic smooth muscle Am J Physiol Gastrointest Liver Physiol, October 1, 2001; 281(4): G964 - G973. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. P. Sergeant, M. A. Hollywood, K. D. McCloskey, N. G. McHale, and K. D. Thornbury Role of IP3 in modulation of spontaneous activity in pacemaker cells of rabbit urethra Am J Physiol Cell Physiol, May 1, 2001; 280(5): C1349 - C1356. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
O. Bayguinov, B. Hagen, and K. M. Sanders Muscarinic stimulation increases basal Ca2+ and inhibits spontaneous Ca2+ transients in murine colonic myocytes Am J Physiol Cell Physiol, March 1, 2001; 280(3): C689 - C700. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
O. Bayguinov, B. Hagen, A. D. Bonev, M. T. Nelson, and K. M. Sanders Intracellular calcium events activated by ATP in murine colonic myocytes Am J Physiol Cell Physiol, July 1, 2000; 279(1): C126 - C135. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
