Insulin potentiates the response to capsaicin in dorsal root ganglion neurons in vitro and muscle afferents ex vivo in normal healthy rodents

Systemic insulin administration evokes sympathoexcitatory actions, but the mechanisms underlying these observations are unknown. We reported that insulin sensitizes the response of thin‐fibre primary afferents, as well as the dorsal root ganglion (DRG) that subserves them, to mechanical stimuli. However, little is known about the effects of insulin on primary neuronal responses to chemical stimuli. TRPV1, whose agonist is capsaicin (CAP), is widely expressed on chemically sensitive metaboreceptors and/or nociceptors. The aim of this investigation was to determine the effects of insulin on CAP‐activated currents in small DRG neurons and CAP‐induced action potentials in thin‐fibre muscle afferents of normal healthy rodents. Additionally, we investigated whether insulin potentiates sympathetic nerve activity (SNA) responses to CAP. In whole‐cell patch‐clamp recordings from cultured mice DRG neurons in vitro, the fold change in CAP‐activated current from pre‐ to post‐application of insulin (n = 13) was significantly (P