A perfusion technique for the determination of pro-inflammatory mediators induced by intradental application of irritants

Introduction: Several morphological and functional features contribute to the consideration of the tooth as a separate compartment having special type of innervation and special immune mechanisms. This study describes a new method allowing the intradental perfusion of rat incisors for the in vivo assessment of pulpal reaction to inflammatory agents. Methods: Under deep anesthesia, the distal 2-3 mm of each of the rat lower incisors was cut and wrapped in a polyethylene tubing connected to a perfusion chamber made of tigone tubing (ID 1/8 in., volume 100-150 mul). Several groups of rats (n = 5 each) were used for intradental application of either saline, capsaicin (100 mug in 100 mul), or endotoxin (ET, 20 mug in 100 mul) for a period of 40 min followed by filling the tooth chamber with saline and collecting the perfusate every 40 min for a period of 8 h. The collected perfusates were stored at -70 degreesC for subsequent determination of the concentration of prostaglandin E-2 (PGE(2)) and nerve growth factor (NGF) by enzyme-linked immunosorbent assay (ELISA). Results: Dentinal injury produced a moderate increase in the levels of NGF and PGE(2) in incisors perfused with saline. Application of ET or capsaicin, however, produced a highly significant increase in the levels of both mediators. These effects peaked at 1.5-3 h for PGE(2) and at 5 h for NGF. Capsaicin showed the most significant effects. Discussion: The reported results cannot be attributed to any factor other than the inflammation of the incisor's pulp, because the described chamber does not allow any spread or leak of the applied irritants. Further studies using other reagents can allow the determination of. the variation of the levels of the various pro-inflammatory mediators and their modulation by treatment with anti-inflammatory drugs. (C) 2002 Elsevier Science Inc. All rights reserved.