Involvement of capsaicin-sensitive nerves in regulation of insulin secretion and glucose tolerance in conscious mice.
The impact of sensory nerves in glucose-stimulated insulin secretion and glucose tolerance was investigated in conscious mice treated neonatally with either capsaicin (Cap) or vehicle (Veh). At 10-12 wk after Cap, both the early (1 min) insulin secretory response to intravenous glucose (2.8 mmol/kg) (by 67%) and glucose elimination were potentiated (P < 0.05). In contrast, basal insulin, glucagon, and glucose were not affected by Cap. Plasma norepinephrine and epinephrine levels did not differ between Cap- and Veh-treated animals, whereas the increase in plasma insulin levels normally induced by alpha-adrenoceptor blockade by phentolamine was absent after Cap treatment. In isolated islets, the insulin secretory response to glucose (20 mmol/l), carbachol (0.1 mmol/l), or phentolamine (0.5 mmol/l) was not affected after Cap. It is concluded that sensory denervation by Cap results in increased glucose tolerance, which is in part because of a potentiated early insulin response to glucose. This potentiation does not seem secondary to altered plasma catecholamine levels or to altered islet secretory capacity. The results suggest rather that Cap-sensitive nerves, by a local effector function and/or as the afferent loop of a neural reflex, exert inhibitory influences on insulin secretion.
Karlsson
S
S
Department of Medicine, Lund University, Malmö General Hospital, Sweden.
Scheurink
A J
AJ
Steffens
A B
AB
Ahrén
B
B
D000344:Afferent Pathways / Q000187:drug effects / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism*; D002211:Capsaicin / Q000494:pharmacology*; D002217:Carbachol / Q000494:pharmacology; D004837:Epinephrine / Q000097:blood; D005260:Female; D005934:Glucagon / Q000097:blood / Q000378:metabolism; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D006706:Homeostasis; D066298:In Vitro Techniques; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D008815:Mice, Inbred Strains; D009638:Norepinephrine / Q000097:blood; D010646:Phentolamine / Q000494:pharmacology; D012016:Reference Values; D013997:Time Factors
D001786:Blood Glucose; D007328:Insulin; D002217:Carbachol; D005934:Glucagon; D005947:Glucose; D002211:Capsaicin; D009638:Norepinephrine; D004837:Epinephrine; D010646:Phentolamine