Fig. 5.
Normalized concentrations of plasma active GLP-1 before, during, and after continuous intravenous GLP-1 infusion in capsaicin- and vehicle-treated rats. GLP-1 (10 μg·rat−1·h−1) was infused intravenously over 60 min in capsaicin-treated (n = 5) and vehicle-treated (n = 7) rats. Blood was sampled from the saphenous vein before and throughout the infusion for measurement of plasma-active GLP-1 by ELISA. Capsaicin-treated rats and vehicle-treated rats had comparable fasting levels of endogenous GLP-1. Intravenous GLP-1 infusion increased the plasma levels of active GLP-1 within 15 min, and significantly elevated levels were maintained throughout the 60-min infusion in both groups. GLP-1 levels began to drop after the infusion stopped, but they were still elevated above fasting levels at the end of the experiment. At all time points before, during, and after the infusion, plasma levels of active GLP-1 did not differ between capsaicin-treated rats and vehicle-treated rats (P > 0.5). *Significant increase over preinfusion GLP-1 levels for both groups (P < 0.001). The period of infusion is indicated by the heavy double-headed line beneath the x-axis.