Modulation of N-Type Ca Currents by A1-Adenosine Receptor Activation in Male Rat Pelvic Ganglion Neurons

Modulation of voltage-activated Ca channels by adenosine was investigated in male rat major pelvic ganglion (MPG) neurons by using the whole-cell variant of the patch-clamp technique. Adenosine inhibited high voltage-activated (HVA) Ca currents in a concentration-dependent manner with an EC50 of 313 nM and a maximal inhibition of 36%, respectively. Inhibition of HVA Ca currents in adrenergic and cholinergic MPG neurons was similar. Adenosine did not modulate T-type Ca channels present in adrenergic MPG neurons. Reverse transcription-polymerase chain reaction analysis indicated that MPG neurons express mRNAs encoding A1 and A2a receptors. Ca current inhibition by adenosine was mimicked by Ncyclopentyladenosine, an A1-selective agonist (EC50 63 nM) and prevented by 100 nM 8-cyclopentyl-1,3-dipropylxanthine, an A1-selective antagonist. Conversely, CGS 21680, an A2aselective agonist, displayed a relatively low potency (EC5