Neurokinin A in the parotid and submandibular glands of the rat: immunohistochemical localization and effect on protein and peroxidase secretion.

An indirect immunofluorescence technique was used to study the distribution of neurokinin A immunoreactive (NKA-IR) nerve fibres in submandibular and parotid glands of the rat. The functional role of neurokinin A on protein and peroxidase secretion in these glands was evaluated by using in vitro methods. In the parotid gland neurokinin A immunoreactive fibres were mainly distributed around the secretory acini, but some were also in evidence around the stromal blood vessels and ducts. The number of the neurokinin A immunoreactive nerve fibres was lower in the submandibular gland than in the parotid gland. They were mainly distributed around the secretory acini and stromal blood vessels and ducts. In vitro, neurokinin A significantly stimulated the release of total amount of released proteins and peroxidase from parotid gland fragments, while in the submandibular gland only the release of peroxidase was increased. By using SDS polyacrylamide gel electrophoresis (SDS-PAGE) specific changes were found in the release of proteins after neurokinin A stimulation. The results of the present study demonstrate that neurokinin A immunoreactive nerve fibres are present in the rat parotid and submandibular glands. Their localization around the secretory elements of the glands and the effect of neurokinin A in vitro experiments indicates that neurokinin A might have a significant role in the regulation of salivary secretion.