Fig. 5.
Exendin-4 (Ex-4) induces a transient increase in intracellular calcium concentration ([Ca2+]i) in dorsal root ganglia (DRG) neurons. A: representative tracing a single mouse primary cultured DRG neuron treated sequentially with vehicle controls (VC) (Krebs-Ringer solution), 50 nM Ex-4, 10 µM capsaicin (Cap), 10 µM allyl isothiocyanate (AITC), and 100 mM KCl. Left: tracing is from wild-type (WT) animals. Right: tracing from glucagon-like peptide-1 receptor (GLP-1R) knockout (KO) animals. The trace represents an average of 15 responsive cells; among the 200 neurons examined in 3 independent cultures from 3 animals per genotype. B: the Venn diagram illustrates that 12% of the Cap-responsive neurons also respond to Ex-4. Twenty-six percent of the Ex-4 responding sensory neurons were non-Cap responsive, which would indicate that Ex-4 induces a transient increase in [Ca2+]i populations of nonsensory neurons. FR, fura-2 AM response.