AJP - Regulatory, Integrative and Comparative Physiology, Vol 267, Issue 4 1071-R1077, Copyright © 1994 by American Physiological Society
Involvement of capsaicin-sensitive nerves in regulation of insulin secretion and glucose tolerance in conscious mice
S. Karlsson, A. J. Scheurink, A. B. Steffens and B. Ahren
Department of Medicine, Lund University, Malmo General Hospital, Sweden.
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.
