GSBS Student Publications

Title

Phospholipid metabolism is required for M1 muscarinic inhibition of N-type calcium current in sympathetic neurons

Student Author(s)

Mandy L. Roberts

GSBS Program

Neuroscience

UMMS Affiliation

Department of Physiology

Date

3-9-2004

Document Type

Article

Medical Subject Headings

Animals; Arachidonic Acid; Calcium Channels, N-Type; Electrophysiology; GTP-Binding Proteins; Kinetics; Lysophospholipids; Muscarinic Agonists; Neurons; Oxotremorine; Pertussis Toxin; Phospholipases; Phospholipids; Rats; Rats, Sprague-Dawley; Receptor, Muscarinic M1; Superior Cervical Ganglion

Disciplines

Life Sciences | Medicine and Health Sciences | Neuroscience and Neurobiology

Abstract

The signal transduction cascade mediating muscarinic receptor modulation of N-type Ca2+ channel activity by the slow pathway has remained incompletely characterized despite focused investigation. Recently we confirmed a role for the G-protein Gq and identified phospholipase C (PLC), phospholipase A2 (PLA2), and arachidonic acid (AA) as additional molecules involved in N-current inhibition in superior cervical ganglion (SCG) neurons by the slow pathway. We have further characterized this signal transduction cascade by testing whether additional molecules downstream of phosphatidylinositol-4,5-bisphosphate (PIP2) are required. The L-channel antagonist nimodipine was bath-applied to block L-current. Pretreating cells with pertussis toxin (PTX) minimized M2/M4 muscarinic receptor inhibition of N-current by the membrane-delimited pathway. Consistent with our previous studies, pharmacologically antagonizing M1 muscarinic receptors (M1Rs), Gqalpha, PLC, PLA2, and AA minimized N-current inhibition by the muscarinic agonist oxotremorine-M (Oxo-M). When cells were left untreated with PTX, leaving the membrane-delimited pathway intact and the same antagonists retested, Oxo-M decreased whole cell currents. Moreover, inhibited currents displayed slowed activation kinetics, indicating intact N-current inhibition by the membrane-delimited pathway. These findings indicate that the antagonists used to block the slow pathway acted selectively. PLA2 cleaves AA from phospholipids, generating additional metabolites. We tested whether the metabolite lysophosphatidic acid (LPA) mimicked the inhibitory actions of Oxo-M. In contrast to AA, applying LPA did not inhibit whole cell currents. Taken together, these findings suggest that the slow pathway requires M1Rs, Gqalpha, PLC, PIP2, PLA2, and AA for N-current inhibition.

Rights and Permissions

Citation: Eur Biophys J. 2004 May;33(3):255-64. Epub 2004 Mar 5. Link to article on publisher's site

DOI of Published Version

10.1007/s00249-003-0387-7

Related Resources

Link to Article in PubMed

Journal Title

European biophysics journal : EBJ

PubMed ID

15004729