Muscarinic agonists cause calcium influx and calcium mobilization in forebrain neurons in vitro.
We have examined the effects of the muscarinic agonist carbachol on the intracellular free Ca2+ concentration ([Ca2+]i) in primary cultures of neurons from rat forebrain using the Ca2+-sensitive fluorescent dye fura-2. Addition of carbachol increased the [Ca2+]i in approximately 60% of cells studied. Oxotremorine-M, but not pilocarpine, mimicked the effects of carbachol. The response was reduced by 60% on removal of extracellular Ca2+, a finding suggesting that muscarinic receptor activation causes Ca2+ influx in addition to intracellular Ca2+ mobilization. Tetrodotoxin and nitrendipine also significantly reduced the response to carbachol. These studies suggest that the changes in [Ca2+]i produced by activation of muscarinic receptors result in part from mobilization of intracellular Ca2+ and that influx through voltage-sensitive Ca2+ channels also provides a significant contribution to the net [Ca2+]i change observed.
Reynolds
I J
IJ
Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois.
Miller
R J
RJ
D000818:Animals; D001696:Biomechanical Phenomena; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D004027:Diencephalon / Q000166:cytology / Q000378:metabolism*; D009116:Muscarine / Q000502:physiology*; D009474:Neurons / Q000378:metabolism*; D009994:Osmolar Concentration; D010277:Parasympathomimetics / Q000494:pharmacology*; D015290:Second Messenger Systems; D013687:Telencephalon / Q000166:cytology / Q000378:metabolism*
D010277:Parasympathomimetics; D009116:Muscarine; D002217:Carbachol; D002118:Calcium