Fig. 1. Inotropic response to β-adrenoceptor stimulation in healthy (  A ) and diabetic (  B ) rats, under high load. AF = isometric active force normalized per cross-sectional area; NS = not significant.  S -cyanopindolol (β³-adrenoceptor antagonist) , N ^G-nitro-l-arginine methylester (l-NAME; nonspecific nitric oxide synthase [NOS] inhibitor) and vinyl-l-  N -5-(1-imino-3-butenyl)-l-ornithine (l-VNIO; specific NOS1 inhibitor) markedly restored the positive inotropic of β-adrenoceptor stimulation in diabetic rats as compared with healthy rats. Data are mean percentage of baseline value ± SD (n = 8 in each group).