%0 Journal Article %1 Bunemann1997 %A Bunemann, M. %A Brandts, B. %A Pott, L. %D 1997 %J J Physiol %K Acetylcholine/pharmacology Agonists/pharmacology Animals Atria/cytology/drug Carbachol/pharmacology Cultured Down-Regulation Guinea Heart Ion Kinetics M2 Muscarinic Muscarinic/drug Myocardium/cytology/*metabolism Nerve/physiology Pigs Potassium/*metabolism Transport/drug Vagus effects effects/*metabolism effects/metabolism Receptor Cell %P 549-54 %T In vivo downregulation of M2 receptors revealed by measurement of muscarinic K+ current in cultured guinea-pig atrial myocytes %U http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=9218215 %V 501 ( Pt 3) %X 1. Muscarinic K+ current (IK(ACh)) elicited by acetylcholine (ACh) was measured in guinea-pig atrial myocytes, which were either freshly isolated or cultured for up to 8 days. 2. The half-time of activation of inward IK(ACh) by a saturating concentration (10 microM) of ACh decreased from approximately 400 ms (in freshly isolated cells) to 250 ms after 6 days in culture. This was paralleled by an increase in the fast desensitizing component of IK(ACh). The density of steady-state currents was not changed. Downregulation of M2 receptors by long-term treatment of isolated myocytes with carbachol in vitro had opposite effects. 3. The EC50 of ACh for the activation of steady-state IK(ACh) was reduced from 5 x 10(-7) M (day 0) to 8 x 10(-8) M (day 6). The shift in EC50 occurred with a half-time of about 2 days, similar to the recovery from downregulation induced by treating atrial myocytes with carbachol in vitro. 4. The increase in sensitivity to ACh can be accounted for by an approximately 6-fold increase in the density of M2 receptors. 5. It is concluded that sensitization in culture reflects recovery from downregulation of M2 receptors due to the tonic vagal input to the heart in the intact animal.

@article{Bunemann1997, abstract = {1. Muscarinic K+ current (IK(ACh)) elicited by acetylcholine (ACh) was measured in guinea-pig atrial myocytes, which were either freshly isolated or cultured for up to 8 days. 2. The half-time of activation of inward IK(ACh) by a saturating concentration (10 microM) of ACh decreased from approximately 400 ms (in freshly isolated cells) to 250 ms after 6 days in culture. This was paralleled by an increase in the fast desensitizing component of IK(ACh). The density of steady-state currents was not changed. Downregulation of M2 receptors by long-term treatment of isolated myocytes with carbachol in vitro had opposite effects. 3. The EC50 of ACh for the activation of steady-state IK(ACh) was reduced from 5 x 10(-7) M (day 0) to 8 x 10(-8) M (day 6). The shift in EC50 occurred with a half-time of about 2 days, similar to the recovery from downregulation induced by treating atrial myocytes with carbachol in vitro. 4. The increase in sensitivity to ACh can be accounted for by an approximately 6-fold increase in the density of M2 receptors. 5. It is concluded that sensitization in culture reflects recovery from downregulation of M2 receptors due to the tonic vagal input to the heart in the intact animal.}, added-at = {2010-12-14T18:12:02.000+0100}, author = {Bunemann, M. and Brandts, B. and Pott, L.}, biburl = {https://www.bibsonomy.org/bibtex/20046eea16319761abd7489c6530bfaf9/pharmawuerz}, endnotereftype = {Journal Article}, interhash = {19d1fc4125c27ab74ffe9dfe2437a6f4}, intrahash = {0046eea16319761abd7489c6530bfaf9}, issn = {0022-3751 (Print) 0022-3751 (Linking)}, journal = {J Physiol}, keywords = {Acetylcholine/pharmacology Agonists/pharmacology Animals Atria/cytology/drug Carbachol/pharmacology Cultured Down-Regulation Guinea Heart Ion Kinetics M2 Muscarinic Muscarinic/drug Myocardium/cytology/*metabolism Nerve/physiology Pigs Potassium/*metabolism Transport/drug Vagus effects effects/*metabolism effects/metabolism Receptor Cell}, month = {Jun 15}, note = {Bunemann, M Brandts, B Pott, L Research Support, Non-U.S. Gov't England The Journal of physiology J Physiol. 1997 Jun 15;501 ( Pt 3):549-54.}, pages = {549-54}, shorttitle = {In vivo downregulation of M2 receptors revealed by measurement of muscarinic K+ current in cultured guinea-pig atrial myocytes}, timestamp = {2010-12-14T18:20:48.000+0100}, title = {In vivo downregulation of M2 receptors revealed by measurement of muscarinic K+ current in cultured guinea-pig atrial myocytes}, url = {http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=9218215}, volume = {501 ( Pt 3)}, year = 1997 }