ACTIVATION OF CARDIAC SYMPATHETIC AFFERENTS - EFFECTS OF EXOGENOUS ADENOSINE AND ADENOSINE-ANALOGS

Adenosine is released during myocardial ischemia and can cause angina- like chest pain when given by intracoronary administration. We tested the hypothesis that intracoronary adenosine activates cardiac sympathe tic afferent fibers and results in reflex sympathoexcitation. In dogs with sinoaortic denervation and vagotomy, we administered 2 mg of aden osine into the left anterior descending artery over 2 min. Before dipy ridamole infusion, intracoronary adenosine resulted in no change in bl ood pressure or renal sympathetic nerve activity. After dipyridamole i nfusion, which blocks adenosine uptake, intracoronary adenosine result ed in a peak increase in sympathetic activity of 34 +/- 7%. We also in vestigated the adenosine-receptor subtype responsible for this sympath oexcitatory response. We found that the adenosine1 agonist N6-cyclopen tyladenosine elicited a dose-dependent sympathoexcitatory response sim ilar to adenosine but that the adenosine2 agonist 5'-(N-cyclopropyl)ca rboxamidoadenosine failed to elicit a sympathoexcitatory response. We conclude that adenosine activates cardiac sympathetic afferent fibers and leads to a sympathoexcitatory response due to activation of adenos ine1 receptors.