Effects of excitatory neurotransmitters on Ca2+ channel current in smooth muscle cells isolated from guinea‐pig urinary bladder

@article{Nakayama1993EffectsOE,
  title={Effects of excitatory neurotransmitters on Ca2+ channel current in smooth muscle cells isolated from guinea‐pig urinary bladder},
  author={Shinsuke Nakayama},
  journal={British Journal of Pharmacology},
  year={1993},
  volume={110}
}
  • S. Nakayama
  • Published 1 September 1993
  • Biology
  • British Journal of Pharmacology
1 A whole‐cell voltage clamp technique was used to examine the effects of purinoceptor and muscarinic receptor agonists on voltage‐sensitive Ca2+ channels in guinea‐pig isolated urinary bladder cells. 2 When the cell membrane was clamped at the holding potential, rapid application of ATP elicited a large inward current in normal solution containing 2.5 mm Ca2+, and reduced the subsequent Ca2+ channel current evoked by a depolarizing pulse (0 mV). Carbachol (CCh) elicited little membrane current… 

Long Ca2+ channel opening induced by large depolarization and Bay K 8644 in smooth muscle cells isolated from guinea‐pig detrusor

It is concluded that L‐type Ca2+ channels in guinea‐pig detrusor cells are open for much longer after large depolarizations consistent with their being two channel open states, and that Bay K 8644 prolongs the lifetime of both open states.

Muscarinic suppression of Ca2+ current in smooth muscle cells of the guinea‐pig urinary bladder

It appears that CCh suppresses ICa via two independent mechanisms: (1) Ca(2+)‐mediated inactivation of the Ca2+ channel, which is caused byCa2+ release from InsP3‐ and TG‐sensitive internal stores, and (2) a GTP‐binding protein‐mediated mechanism, which requires intracellular Ca2+.

The α1‐subunit of smooth muscle Ca2+ channel preserves multiple open states induced by depolarization

The sum of unitary channel currents revealed that the tail current seen after large conditioning depolarization had a slower deactivation time constant compared to that seen when the cell membrane was depolarized briefly with a test step, suggesting that large depolarizations transform the conformation of the Ca2+ channels to a second open state.

Possible contribution of long open state to noninactivating Ca2+ current in detrusor cells.

Differences in the voltage dependence of the development of the long open state in various smooth muscles, as well as differences in the equilibrium constant between open and inactivated states, could underlie the different patterns of contractile behavior that characterize smooth muscles.

Slow deactivation and U-shaped inactivation properties in cloned Ca[v]1.2b channels in Chinese hamster ovary cells

A kinetic scheme with one closed state, two open states ( O 1, O 2 ) and two inactivated states linked to the closed state and open state O 1 , respectively, protected from inactivation is drawn up, suggesting involvement of physical processes in the channel protein.

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