title: Pretreatment with an adenosine A1 receptor agonist and lidocaine: a possible alternative to myocardial ischemic preconditioning.
abstract: OBJECTIVE
  The heart possesses an extraordinary ability to remember short episodes of sublethal ischemia and reperfusion (angina), which protects the myocardium and coronary vasculature from a subsequent lethal insult, a phenomenon known as ischemic preconditioning. A therapeutic goal for more than 2 decades has been to develop a pharmacologic mimetic comparable with ischemic preconditioning. Our aim was to investigate the preconditioning effect of a new combinatorial therapy targeting adenosine A1 receptors and voltage-dependent sodium fast channels in the in vivo rat model of regional ischemia.
  
  
  METHODS
  Ischemia-reperfusion was achieved by placing a reversible tie around the left coronary artery in anesthetized and ventilated Sprague-Dawley rats (n = 37). Rats were randomly assigned to 1 of 5 groups: (1) saline control (n = 13); (2) ischemic preconditioning (n = 6); (3) lidocaine only (608 microg . kg -1 . min -1 , n = 5); (4) adenosine A1 receptor agonist 2-chloro-N6-cyclopentyladenosine (CCPA; 5 microg/kg, n = 7); and (5) CCPA plus lidocaine (n = 6). Ischemic preconditioning was achieved by using 3 cycles of ischemia and reperfusion lasting 3 minutes each. Lidocaine was infused continuously 5 minutes before and throughout 30 minutes of ischemia and ceased at reperfusion. A bolus of CCPA was infused 5 minutes before ligation along with a constant infusion of lidocaine (as above). All animals were reperfused for 120 minutes for infarct size measurement.
  
  
  RESULTS
  Fifty-four percent of saline control rats, 17% of ischemic preconditioning-treated rats, and 29% of CCPA-treated rats died during ischemia from ventricular fibrillation. Infarct size of saline control animals was 61% +/- 5%. Pretreating with CCPA and lidocaine infusion resulted in no deaths, no severe arrhythmias, and significant infarct size reduction compared with that seen in saline control animals (P < .05). Remarkably, infarct size reduction in CCPA plus lidocaine-treated rats (12% +/- 4%) was equivalent to that achieved with ischemic preconditioning (11% +/- 3%), whereas infarct size in rats undergoing CCPA-only and lidocaine-only treatments was 42% +/- 7% and 60% +/- 6%, respectively. Although CCPA plus lidocaine treatment reduced heart rate, mean arterial pressure, and systolic pressure during ischemia, no correlation was found between these variables and infarct size reduction.
  
  
  CONCLUSIONS
  We conclude that activating adenosine A1 receptor subtype with CCPA and concomitantly modulating sodium fast channels with lidocaine was comparable with ischemic preconditioning and might offer a new therapeutic window to minimize myocardial damage during surgical ischemia and reperfusion.
authors.affiliation: Department of Physiology and Pharmacology, James Cook University, Queensland, Australia.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Canyon
authors.forename: Geoffrey P
authors.initials: GP
authors.lastname: Dobson
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D058907:Adenosine A1 Receptor Agonists; D000818:Animals; D002317:Cardiovascular Agents / Q000494:pharmacology / Q000627:therapeutic use*; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D008012:Lidocaine / Q000494:pharmacology / Q000627:therapeutic use*; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000503:physiopathology / Q000517:prevention & control*; D051381:Rats; D017207:Rats, Sprague-Dawley; D043682:Receptor, Adenosine A1 / Q000187:drug effects; D015222:Sodium Channels / Q000187:drug effects
chemical_list: D058907:Adenosine A1 Receptor Agonists; D002317:Cardiovascular Agents; D043682:Receptor, Adenosine A1; D015222:Sodium Channels; C058394:2-chloro-N(6)cyclopentyladenosine; D008012:Lidocaine; D000241:Adenosine