['The primary ain of this study was to investigate the effect of carbachol on ventricular repolarisation in an intact animal heart.', 'In five sheep, carbachol was administered to the left circumflex coronary artery (LCX) at 1.0 and 2.5 micromol/ml/min respectively for 3 min. Multiple unipolar ECGs were acquired from the epicardium of LCX territory. Administration of carbachol at 2.5 micromol/ml/min was also repeated after pre-treatment with nitro-L-arginine (20 mg/kg), a nitric oxide synthase inhibitor.', 'Carbachol at 1.0 or 2.5 micromol/ml/min resulted in a T wave inversion and ARI prolongation in the LCX territory. The increase in ARI at 1.0 and 2.5 micromol/ml/min was 38 +/- 17 and 58 +/- 14 ms respectively (p<0.05). T wave inversion and ARI prolongation at 2.5 micromol/ml/min was diminished by pre-treatment with nitro-L-arginine.'] Does carbachol prolong ventricular repolarisation through nitric oxide release in an intact heart?