Neonatal capsaicin-treatment in mice: effects on pancreatic peptidergic nerves and 2-deoxy- d-glucose-induced insulin and glucagon secretion

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It is not known whether sensory nerves are involved in the insulin, glucagon or glucose responses to autonomic nerve activation induced by 2-deoxy- d-glucose (2-DG). We therefore treated mice neonatally with capsaicin which permanently destroys sensory afferent nerve fibers. Immunohistochemistry of the pancreas at 13–14 weeks of age revealed a substantial reduction of calcitonin gene-related peptide (CGRP)-immunoreactive nerves and a partial reduction of substance P-immunoreactive nerves. In contrast, no effect was observed on galanin-immunoreactive nerves. At age 10–12 weeks, the mice were injected intravenously with 2-DG (500 mg/kg). In controls, 2-DG stimulated insulin and glucagon secretion and induced hyperglycemia ( P < 0.01). Capsaicin treatment partially reduced the glucose and glucagon responses to 2-DG ( P < 0.01). In contrast, the insulin response to 2-DG was not affected by capsaicin. It is concluded that the mouse pancreas contains capsaicin-sensitive sensory CGRP- and substance P-immunoreactive nerve fibers, whereas the galanin-immunoreactive nerve fibers are not sensitive to capsaicin. Furthermore, capsaicin-sensitive sensory nerve fibers are partially involved in 2-DG-induced glucagon secretion and hyperglycemia, whereas sensory nerves are not involved in 2-DG-induced insulin secretion.