Muscarinic Receptor Activation Modulates Ca Channels in Rat Intracardiac Neurons via a PTX- and Voltage-Sensitive Pathway

patch-clamp technique, effects of the potent muscarinic agonist oxotremorine methiodide ( oxo-M ) on voltage-activated Ca 2/ I N T R O D U C T I O N channel currents were investigated in acutely dissociated adult Acetylcholine (ACh) is the principal transmitter at both rat intracardiac neurons. In all tested neurons oxo-M reversibly preganglionic and postganglionic synapses in parasympainhibited the peak Ba 2/ current. Inhibition of the peak Ba 2/ thetic intracardiac ganglia. Activation of the postjunctional current by oxo-M was associated with slowing of activation M2 muscarinic receptor in the myocardium exerts negative kinetics and was concentration dependent. The concentration chronotropic, dromotropic, and inotropic responses (for reof oxo-M necessary to produce a half-maximal inhibition of view see Löffelholz and Pappano 1985). Postsynaptic muscurrent and the maximal inhibition were 40.8 nM and 75.9%, carinic receptors also have important roles in the modulation respectively. Inhibitory effect of oxo-M was completely abol-