Aims/hypothesis: A considerable proportion of whole-body insulin-stimulated glucose uptake is dependent upon the hepatic insulin-sensitising substance ( HISS) in a pathway mediated by the hepatic parasympathetic nerves (HPNs). We tested the hypothesis that a high-sucrose diet leads to the impairment of the HPN-dependent component of insulin action. Methods: We quantified insulin sensitivity using the rapid insulin sensitivity test, a modified euglycaemic clamp. Quantification of the HPN-dependent component was achieved by administration of a muscarinic receptor antagonist ( atropine, 3 mg/kg). Results: Insulin sensitivity was higher in standard-fed than in sucrose-fed Wistar rats (305.6 +/- 34.1 vs 193.9 +/- 13.7 mg glucose/kg body weight; p < 0.005) and Sprague-Dawley rats (196.4 +/- 5.9 vs 95.5 +/- 16.3 mg glucose/kg body weight; p < 0.01). The HPN-independent component was similar in the two diet groups. Insulin resistance was entirely due to an impairment of the HPN-dependent component in both Wistar rats (164.3 +/- 28.1 [standard-fed] vs 26.5 +/- 7.5 [sucrose-fed] mg glucose/kg body weight; p < 0.0001) and Sprague-Dawley rats (111.7 +/- 9.5 vs 35.3 +/- 21.4 mg glucose/kg body weight; p < 0.01). Furthermore, HPN-dependent insulin resistance in Sprague-Dawley rats was already evident after 2 weeks of a high-sucrose diet (28.5 +/- 7.6 [2 weeks], 35.3 +/- 21.4[6 weeks], 17.9 +/- 5.4 [9 weeks] mg glucose/kg body weight) and was independent of the nature of sucrose supplementation (12.3 +/- 4.7 [solid] and 17.9 +/- 5.4 [liquid] mg glucose/kg body weight). Conclusions/interpretation: Our results support the hypothesis that insulin resistance caused by sucrose feeding is due to an impairment of the HPN-dependent component of insulin action, leading to a dysfunction of the HISS pathway.