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Sensory innervation of the viscera serves a number of important functions, including regulation of visceral motility and secretory activity, and transmission of visceral sensations, including pain. There are many ways in which the sensitivity of visceral sensory neurones might be modulated, and these are discussed. Altered sensory neurone responsiveness may contribute to pathophysiological states such as irritable bowel syndrome, and the mechanisms leading to sensory neurone sensitisation offer novel targets for the treatment of such disorders.

The 7S nerve growth factor molecule, found in the mouse submandibular gland, is comprised of three distinct protein subunits named alpha, gamma and beta-NGF. In this paper, radioimmunoassays specific for each subunit were used to measure the concentrations of these subunits in homogenates of mouse submandibular gland. It was determined that there were excess concentrations of both the alpha and gamma subunits, more than enough to bind all of the beta-NGF in the gland to form 7S-NGF. The radioimmunoassay data was confirmed by gel filtration experiments. In the gel filtration experiments, the excess alpha and gamma subunits eluted at positions which would indicate that these excess subunits were free and not bound in the 7S-NGF complex. The identity of the excess alpha and gamma subunits was substantiated by ion exchange chromatography, isoelectric focusing polyacrylamide gels and immunoblotting experiments. In conclusion, there are considerable quantities of alpha and gamma subunits present in the submandibular gland which are not bound to beta-NGF. The functional significance of these excess concentrations of the alpha and gamma subunits is not known.