Central glucagon antagonizes morphine- and stress-induced antinociception in the mouse.

: Previously, we have demonstrated that glucagon antagonizes morphine-induced antinociception in the rat (Malcolm et al. 1985). In the present studies we have shown that central injection of glucagon antagonizes morphine- and stress-induced antinociception in the mouse. Since stress-induced antinociception is mediated by the activation of endogenous opioid systems, these findings provide the first evidence for glucagon's ability to antagonize endogenous opioid actions.