Bombesin-like immunoreactivity in sympathetic ganglia.

Nerve fibres showing immunoreactivity for bombesin have been observed in prevertebral sympathetic ganglia of the rat and guinea-pig. The distribution of bombesin immunoreactive fibres was compared with the distribution of the structurally-related peptide substance P. Dense networks of varicose bombesin immunoreactive fibres were observed, and in the rat coeliac ganglion the density exceeded that of the substance P immunoreactive fibres. Extracts of rat and guinea-pig coeliac ganglion contained material cross-reacting in radioimmunoassays for bombesin tetradecapeptide. Similar concentrations of bombesin and substance P were found in the guinea-pig ganglion, whereas in the rat the concentration of bombesin was about 20 times as high as that of substance P. Two molecular forms of immunoreactive bombesin were identified, neither of which corresponded exactly to synthetic bombesin. The two components were also distinguishable from synthetic substance P. A potential role of a bombesin-like peptide in neural pathways between the gut and prevertebral ganglia is suggested.