Inhibition in Rat Sympathetic Stellate Ganglion Neurons

Muscarinic acetylcholine receptors (mAChR) are known to mediate the acetylcholine inhibition of Ca 2+ channels in central and peripheral neurons. Stellate ganglion (SG) neurons provide the main sympathetic input to the heart and contribute to the regulation of heart rate and myocardial contractility. Little information is available regarding mAChR regulation of Ca 2+ channels in SG neurons. The purpose of the present study was to identify the mAChR subtypes that modulate Ca 2+ channel currents in rat SG neurons innervating heart muscle. Accordingly, the modulation of Ca 2+ channel currents by the muscarinic cholinergic agonist, oxotremorine-methiodide (Oxo-M) and mAChR blockers was examined. Oxo-M-mediated mAChR stimulation led to inhibition of Ca 2+ currents through voltage-dependent (VD) and voltage-independent (VI) pathways. and M 2 receptors are expressed and located on the surface of SG neurons. Overall, the results indicate that SG neurons which innervate cardiac muscle express M 1 and M 2 mAChR, and activation of these receptors leads to inhibition of Ca 2+ channel currents through VI and VD pathways, respectively.