Characterization of central inhibitory muscarinic autoreceptors by the use of muscarinic acetylcholine receptor knock-out mice

• Type of Material: Article
• Authors: Weilie Zhang, National Institute of Diabetes and Digestive and Kidney Diseases; Anthony S. Basile, National Institute of Diabetes and Digestive and Kidney Diseases; Jesus Gomeza, National Institute of Diabetes and Digestive and Kidney Diseases; Laura A. Volpicelli, Emory University; Allan I Levey, Emory University; Jurgen Wess, National Institute of Diabetes and Digestive and Kidney Diseases
• Language: English
• Date: 2002-03-01
• Publisher: Lippincott, Williams & Wilkins
• Publication Version: Final Published Version
• Copyright Statement: Copyright © 2002 Society for Neuroscience
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1523/JNEUROSCI.22-05-01709.2002
• Title of Journal or Parent Work: Journal of Neuroscience Nursing
• ISSN: 0888-0395
• Volume: 22
• Issue: 5
• Start Page: 1709
• End Page: 1717
• Grant/Funding Information: This work was supported by a Cooperative Research and Development Alliance between the National Institute of Diabetes and Digestive and Kidney Diseases (J.W.) and the Eli Lilly Research Laboratories; National Institutes of Health Grant NS30454 (A.L.); and the Alzheimer Association (A.L.).
• Keywords: mice; knockout; autoreceptors; SUBTYPE-SPECIFIC ANTIBODIES; presynaptic; IN-VIVO; receptors; STIMULATION; ALZHEIMERS-DISEASE; CEREBRAL-CORTEX; RELEASE; muscarinic receptors; acetylcholine release; Science & Technology; Neurosciences; LOCALIZATION; Neurosciences & Neurology; Life Sciences & Biomedicine; BRAIN; oxotremorine; RAT STRIATUM; MODULATION
• Research Categories: Biology, Neuroscience

Abstract

Forebrain muscarinic acetylcholine (ACh) receptors (mAChRs; M1-M5) are predicted to play important roles in many fundamental central functions, including higher cognitive processes and modulation of extrapyramidal motor activity. Synaptic ACh levels are known to be regulated by the activity of presynaptic muscarinic autoreceptors mediating inhibition of ACh release. Primarily because of the use of ligands with limited receptor subtype selectivity, classical pharmacological studies have led to conflicting results regarding the identity of the mAChR subtypes mediating this activity in different areas of the brain. To investigate the molecular identity of hippocampal, cortical, and striatal inhibitory muscarinic autoreceptors in a more direct manner, we used genetically altered mice lacking functional MLaboratory of Bioorganic Chemistry2 and/or M4 mAChRs [knock-out (KO) mice]. After labeling of cellular ACh pools with [3H]choline, potassium-stimulated [3H]ACh release was measured in superfused brain slices, either in the absence or the presence of muscarinic drugs. The nonsubtype-selective muscarinic agonist, oxotremorine (0.1-10 μM), inhibited potassium-stimulated [3H]ACh release in hippocampal, cortical, and striatal slices prepared from wild-type mice by up to 80%. This activity was totally abolished in tissues prepared from M2-M4 receptor double KO mice. Strikingly, release studies with brain slices from M2 and M4 receptor single KO mice indicated that autoinhibition of ACh release is mediated primarily by the M2 receptor in hippocampus and cerebral cortex, but predominantly by the M2 receptor in the striatum. These results, together with additional receptor localization studies, support the novel concept that autoinhibition of ACh release involves different mAChRs in different regions of the brain.