Distribution and roles of substance P in human parotid duct

Sialadenitis occurs with greatest frequency in the parotid glands because infection and inflammation arise easily from the oral cavity. Since patients often experience severe swelling and pain during inflammation, the distribution of sensory nerves in these ducts may have clinical significance. We used antibodies to the known neuropeptide substance P and to tyrosine hydroxylase - a marker of adrenergic fibres - to observe their distribution and gain insight on their functional role in adult human parotid duct. After excising the parotid duct along with the gland, specimens were divided into three regions: the tract adjacent to the parotid gland, the route along the anterior surface of the masseter, and the area where the duct penetrates the buccinator muscle and opens into the oral cavity. Specimens were prepared and examined under a fluorescence microscope following immunostaining. Substance P positivity was observed in all three regions of the duct, whereas tyrosine hydroxylase was distributed mainly in the vascular walls and surrounding areas. The distribution of substance P candidates this molecule to assist in tissue defense in conjunction with the blood and lymph vessels of this area. Tyrosine hydroxylase in the blood vessel wall likely contributes to regulation of blood flow in concert with substance P positive nerves surrounding the blood vessels.