Altered extracellular signal-regulated kinase signal transduction by the muscarinic acetylcholine and metabotropic glutamate receptors after cerebral ischemia.
To determine whether muscarinic acetylcholine receptors (mAChR) in the post-ischemic hippocampus may be involved in altered extracellular signal-regulated kinases (ERK) signal transduction, we have investigated changes in the activity of ERK1/2 induced by a muscarinic agonist, carbachol. Cerebral ischemia was produced in the rat by injecting 900 microspheres (48 microm in diameter) into the right internal carotid artery. Applying carbachol to the contralateral hippocampal slices from ischemic rats increased the phosphorylation of ERK1/2 but did not increase phosphorylation in the ipsilateral hippocampus. Analysis of M(1) mAChR binding showed that there was no significant difference in the number and K(d) values between the hippocampi from naïve and ischemic rats. Immunoblotting analysis showed no significant difference in the amount of M(1) mAChR in both hemispheres. In contrast to carbachol stimulation, the protein kinase C activator induced an activation of ERK1/2 in the ipsilateral hippocampus. This increase was shown to occur in neurons by immunofluorescence colocalization study. Carbachol-stimulated tyrosine phosphorylation of the G alpha(q/11), inositol 1,4,5-trisphosphate formation, and association of G alpha(q/11) with phospholipase C beta 1 were attenuated in the ipsilateral hippocampus. We also found that stimulation of group I metabotropic glutamate receptors, which are linked to G alpha(q/11), failed to increase in phosphorylation of ERK1/2 in the ipsilateral hippocampus. These results suggest that failure in receptor-mediated tyrosine phosphorylation of the G alpha(q/11) subunit and a defect in receptor-G alpha(q/11-)effector coupling in the ischemic hippocampus may be involved in alterations of ERK signal transduction.
Takagi
Norio
N
Faculty of Pharmaceutical Sciences, Department of Pharmacology, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan. takagino@ps.toyaku.ac.jp
Miyake-Takagi
Keiko
K
Takagi
Kaori
K
Tamura
Hiroshi
H
Takeo
Satoshi
S
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002545:Brain Ischemia / Q000503:physiopathology*; D002217:Carbachol / Q000494:pharmacology; D007839:Functional Laterality; D006624:Hippocampus / Q000503:physiopathology*; D066298:In Vitro Techniques; D020766:Intracranial Embolism / Q000503:physiopathology; D007700:Kinetics; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D043643:Receptor, Muscarinic M1; D018094:Receptors, Metabotropic Glutamate / Q000502:physiology*; D011976:Receptors, Muscarinic / Q000502:physiology*; D012016:Reference Values; D015398:Signal Transduction / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D043643:Receptor, Muscarinic M1; D018094:Receptors, Metabotropic Glutamate; D011976:Receptors, Muscarinic; D001285:Atropine; D002217:Carbachol; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate