Pharmacological Pre-Conditioning by b-adrenoceptor stimulation (b-AR)has been described as a mechanism to protect the post- ischemic heart against morphological damage and to improve functional recovery. This may be of potential benefit compared with classical pre-conditioning that also reduces post-ischemic infarct size but has only minor effects on the acute functional recovery of the post-ischemic heart. The present study was aimed to charcaterize the effect of pre-ischemic applicated isoprenaline

(ISO), a b-AR agonist, on the post-ischemic functional recovery. Rat hearts were exposed to 45 min zero-flow ischemia and 90 min reperfusion. Left ventricular developed pressure (LVDP), heart rate (HR), perfusion pressure (PP), +dP/dt, and -dP/dt were determined. ISO concentration-dependently increased cardiac performance before ischemia at concentrations above 1 nM. b-AR did not desensitize during ischemia. Preischemic application of ISO at 1-100 pM, thus at concentrations below those that exert a inotropic effect before ischemia, ISO concentration-dependently improved post-ischemic recovery. This effect of ISO was attenuated by the co-presence of atenolol. Higher concentrations of ISO were able to improve post-ischemic receovery when washed out before ischemia but not if they were present during ischemia. In conclusion low adrenergic drive during ischemia improves post-ischemic recovery and may explain the so-called pharmacoplogical pre-conditioning effect of b-AR stimulation.