Immunohistochemical indications of gastrin releasing peptide--bombesin-like immunoreactivity in the nervous system of the rat. Codistribution with substance P-like immunoreactive nerve terminal systems and coexistence with substance P-like immunoreactivity in dorsal root ganglion cell bodies.

Weak to strong gastrin releasing peptide--bombesin (GRP-Bn)-like immunoreactivity was found in fine varicose nerve terminal systems of low to high densities in several parts of the CNS. The highest densities of strongly immunoreactive terminals were found in the marginal layer and in the substantia gelatinosa of the spinal cord, and in parts of the nuc. tractus spinalis nervi trigemini. Morphometrical analysis in the spinal cord demonstrates that GRP-BN-like-immunoreactive and substance P (SP), but not somatostatin (SS)-immunoreactive nerve terminals strikingly codistribute. Coexistence of SP and GRP-BN-like immunoreactivities was demonstrated in trigeminal and spinal ganglion nerve cells. Thus, GRP-BN-like immunoreactivity may coexist with SP in certain SP-immunoreactive nerve terminal systems.