Effect of substance P administration on vascular permeability in the rat dental pulp and submandibular gland.

Abstract

The effects of substance P (SP) administration on vascular permeability were studied in the dental pulp (DP) of upper and lower incisors and in the submandibular gland (SMG) of male rats. Vascular permeability was assessed by means of extravasation of Evans blue dye. SP was diluted in 0.5% bovine serum albumin (BSE) and infused into the left common carotid artery. Separate groups of animals receive chloropyramine, an H1 histamine receptor antagonist (10 mg kg-1 i.v.) or indomethacin, a prostaglandin synthesis inhibitor (4 mg kg-1 i.v.) prior to SP infusions. Infusion of SP for 5 min increased plasma extravasation both in DP and SMG, with a threshold of about 30 pmol min-1 and 74 pmol min-1, respectively. Enhanced salivary secretion was also observed. Although the administration of 74 pmol min-1 of SP significantly lowered the systemic blood pressure, experimental hypotension elicited by haemorrhage did not influence vascular permeability in either organ tested. After chloropyramine administration the SP effect on vascular permeability in both DP and SMG was abolished. Indomethacin pretreatment failed to prevent the permeability-enhancing action of SP. Our results suggest that substance P increases both pulpal and glandular plasma extravasation in the rat indirectly, via the release of histamine and the activation of H1 histamine receptors.