PHYSIOLOGICAL RESEARCH ISSN 0862-8408 © 2006 Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic Fax +420 241 062 164 E-mail: physres@biomed.cas.cz http://www.biomed.cas.cz/physiolres Physiol. Res. 55: 1-8, 2006 Dopamine Mimics the Cardioprotective Effect of Ischemic Preconditioning via Activation of α 1 -Adrenoceptors in the Isolated Rat Heart A. LAZOU 1 , T. MARKOU 1 , M. ZIOGA 1 , E. VASARA 1 , A. EFSTATHIOU 1 , C. GAITANAKI 2 1 Laboratory of Animal Physiology, Department of Zoology, School of Biology, Aristotle University of Thessaloniki, Thessaloniki and 2 Department of Animal and Human Physiology, School of Biology, University of Athens, Athens, Greece Received August 30, 2004 Accepted March 3, 2005 On-line available April 26, 2005 Summary The aim of the present study was to clarify whether pharmacological preconditioning with dopamine protects the heart against ischemia and whether this effect is mediated through dopaminergic receptors (D 1 and D 2 ) or α 1 -adrenoceptors. Isolated perfused rat hearts were either non-preconditioned, preconditioned with 5 min ischemia, or treated for 5 min with dopamine (1, 5 or 10 μM) before being subjected to 45 min of sustained ischemia followed by 60 min reperfusion. Postischemic functional recovery and infarct size were used as indices of the effects of ischemia. Treatment with the lower concentration of dopamine (1 μM), did not provide any protection to the ischemic myocardium. On the other hand, treatment with 5 μM dopamine resulted in significantly improved functional recovery, whereas administration of dopamine (10 μM) resulted in significantly improved functional recovery as well as reduction of infarct size. Pretreatment with the mixed D 1 /D 2 dopaminergic receptor antagonist haloperidol or the β-adrenoceptor selective antagonist propranolol did not attenuate the protective effect of pharmacological preconditioning with 10 μM dopamine with respect to both functional recovery and infarct size reduction. On the other hand, the cardioprotective effect of dopamine was blocked when the α 1 -adrenoceptor selective antagonist, prazosin, was administered. In conclusion, pharmacological preconditioning with dopamine protects the myocardium against ischemia and this effect seems to be mediated through activation of α 1 -adrenoceptors. Key words Heart • Preconditioning • Dopamine • Ischemia Introduction Brief periods of acute myocardial ischemia protect the heart against subsequent episodes of prolonged ischemia/reperfusion. This phenomenon is termed ischemic preconditioning (IP) and was first demonstrated in a canine model by Murry et al. (1986). In experimental animals and humans, ischemic