Studies were performed on the effects of activation of afferent nerves with capsaicin (5 mg/kg i.p.) and lesioning of these nerves with neurotoxic doses of capsaicin (50 mg/kg, s.c. in two-day-old rats and 200 mg/kg s.c. in adult rats) on serum glucose and free fatty acid (FFA) concentrations in conditions of changing glucose levels induced by administration of insulin and glucose to starved (16 h) Wistar rats. These studies showed that capsaicin stimulation of intact rats decreased the hypoglycemic action of insulin, increased hyperglycemia following glucose dosage, increased FFA levels, and prevented the FFA-lowering effect of insulin. Neonatal treatment with capsaicin decreased the hypoglycemic effect of insulin but had no effect on hyperglycemia following glucose doses, but decreased FFA levels. Treatment of adult rats with neurotoxic doses of capsaicin did not alter the effect of insulin on glucose levels and decreased FFA concentrations. Capsaicin stimulation in rats following treatment with neurotoxic doses had no effect on the hypoglycemic action of insulin, but prevented it from affecting the FFA concentration.

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