Effect of bombesin and substance P on the smooth muscle of the chicken crop

Abstract

The effect of bombesin and of substance P was investigated in smooth muscle strips of the chicken crop. Bombesin in picomolar concentration (0.1 x 10(-12) - 5 X 10(-12) mol/l) caused a concentration-related contraction of the muscle strips. Substance P in nanomolar concentration (0.1 x 10(-9) - 10 x 10(-9) mol/l) was effective in the same manner. Tetrodotoxin (2 x 10(-7) mol/l) did not influence the contraction responses to either bombesin or substance P. The excitatory effect of bombesin and of substance P did not follow activation of cholinergic receptors since their effect on the crop smooth muscle was not antagonized by atropine (10(-4) mol/l) or by hexamethonium (10(-4) mol/l). Strips stored for 24 hours in the Tyrode's solution at 4 degrees C without a supply of oxygen maintained their full sensitivity to bombesin and to substance P. These results are consistent with a direct action of bombesin and substance P on the crop smooth muscle.

Radioligand binding and functional characterisation of tachykinin receptors in chicken small intestine

“…It is apparent that region-specific mechanisms are involved and that the enteric circuitry and contractile mechanisms are at least as complex (if not more so) than in mammals. Previous studies in the chicken crop (storage chamber) and caecum have found only a direct myogenic mechanism to be involved in the contraction to SP (Brodin et al 1981;Denac and Scharrer 1988). In contrast, our study in ileal longitudinal muscle clearly showed that neuronal mechanisms accounted for ~60% of the total contractile response, as seen for SP in a previous study focusing on mechanisms of action of cholecystokinin (Martin et al 1994).…”