Muscarinic suppression of the M-current is mediated by a rise in internal Ca2+ concentration.
The role of intracellular Ca2+ in the muscarinic suppression of M-current was examined. Intracellular injection of Ca2+ buffer into cells in the intact ganglion reduced the response to muscarinic agonist. In similar experiments on isolated cells, Ca2+ buffer was introduced into the cytoplasm using a perfused recording pipette. Ca2+ buffer (20 mM) with the free Ca2+ concentration set to normal resting levels produced a reversible reduction of the muscarinic response. In a second line of investigation, it was found that pharmacological procedures designed to deplete internal stores of Ca2+ produced a decrease in the muscarinic response. These results, taken together with previous work, support the hypothesis that the muscarinic suppression of M-current is mediated by the release of Ca2+ from intracellular stores.
Kirkwood
A
A
Department of Biology, Brandeis University, Waltham, Massachusetts 02254.
Simmons
M A
MA
Mather
R J
RJ
Lisman
J
J
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology* / Q000031:analogs & derivatives; D004553:Electric Conductivity / Q000187:drug effects; D005071:Evoked Potentials / Q000187:drug effects; D005728:Ganglia, Sympathetic / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D009116:Muscarine / Q000494:pharmacology*; D011892:Rana catesbeiana; D013569:Synapses / Q000187:drug effects / Q000502:physiology
D002110:Caffeine; D004533:Egtazic Acid; D009116:Muscarine; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium