Muscarinic acetylcholine receptor activation enhances hippocampal neuron excitability and potentiates synaptically evoked Ca(2+) signals via phosphatidylinositol 4,5-bisphosphate depletion.
Using single cell Ca(2+) imaging and whole cell current clamp recordings, this study aimed to identify the signal transduction mechanisms involved in mACh receptor-mediated, enhanced synaptic signaling in primary cultures of hippocampal neurons. Activation of M(1) mACh receptors produced a 2.48 +/- 0.26-fold enhancement of Ca(2+) transients arising from spontaneous synaptic activity in hippocampal neurons. Combined imaging of spontaneous Ca(2+) signals with inositol 1,4,5-trisphosphate (IP(3)) production in single neurons demonstrated that the methacholine (MCh)-mediated enhancement required activated G(q/11)alpha subunits and phospholipase C activity but did not require measurable increases in IP(3). Electrophysiological studies demonstrated that MCh treatment depolarized neurons from -64 +/- 3 to -45 +/- 3 mV and increased action potential generation. Depletion of plasma membrane phosphatidylinositol 4,5-bisphosphate (PIP(2)) enhanced neuronal excitability and prolonged the action of MCh. These studies suggest that, in addition to producing the second messengers IP(3) and diacylglycerol, mACh receptor activation may directly utilize PIP(2) hydrolysis to regulate neuronal excitability.
Department of Cell Physiology and Pharmacology, Medical Sciences Building, University of Leicester, University Road, Leicester, LE1 9HN, UK. kwyl@le.ac.uk
Kenneth W
KW
Young
Daniela
D
Billups
Carl P
CP
Nelson
Neil
N
Johnston
Jonathon M
JM
Willets
Michael J
MJ
Schell
R A John
RA
Challiss
Stefan R
SR
Nahorski
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000502:physiology; D020013:Calcium Signaling / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D005973:Glutamine / Q000502:physiology; D006624:Hippocampus / Q000166:cytology*; D008564:Membrane Potentials / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D018094:Receptors, Metabotropic Glutamate / Q000502:physiology; D011976:Receptors, Muscarinic / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D013569:Synapses / Q000378:metabolism
D015220:Calcium Channels; D019269:Phosphatidylinositol 4,5-Diphosphate; D018094:Receptors, Metabotropic Glutamate; D011976:Receptors, Muscarinic; D016194:Receptors, N-Methyl-D-Aspartate; D005973:Glutamine; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D002118:Calcium