Fig. 10.

Glucose-dependent insulinotropic polypeptide (GIP) induces substance P (SP) release from capsaicin-responsive sensory neurons. The graph depicts SP-sensor (gray bars) response. Mouse primary cultured dorsal root ganglia (DRG) neurons from wild-type (WT) and GIP knockout (KO) animals were cocultured with SP sensors and exposed to 50 nM GIP. GIP induced an increased calcium response in SP-sensors adjacent to capsaicin (Cap)-responsive sensory neurons in DRGs from WT animals (gray bars) but not from GIP KO animals. GIP enhanced the Cap-induced SP secretion. Greater than 400 neurons were examined in 3 independent cultures from 4 mice. Bars are means ± SE (n = 4 animals). NFR, normalized fura-2 AM response; NS, not significant. *P < 0.05, **P < 0.01. Statistical analysis was by ANOVA using Tukey's post hoc test.