A role for bombesin in sensory processing in the spinal cord.

Bombesin (BN)-containing neuronal processes were demonstrated in laminae I and II of the dorsal horn of the cat, rat, and mouse spinal cord by immunocytochemistry and radioimmunoassay. Dorsal rhizotomy in the cat resulted in a marked decrease in BN immunoreactivity in the dorsal horn indicating that BN is contained in primary sensory afferents. BN-binding sites were also localized in superficial laminae of the dorsal horn. The presence of both BN and BN-binding sites in the dorsal horn suggested that BN may be involved in sensory processing in the spinal cord. Consistent with this hypothesis, it was demonstrated that an injection of BN into the spinal cord caused a biting and scratching response indicative of sensory stimulation. The effect was similar to that observed after injection of substance P into the cord with the exception that the BN effect lasted about 100 times longer than that induced by substance P. Taken together, these data indicate that BN may be a neurotransmitter of primary sensory afferents to the spinal cord.