Effects of an inducible nitric oxide synthase inhibitor on experimentally induced rat pulpitis.

Nitric oxide (NO) is a biological effector molecule involved in a large variety of reactions and, as synthesized by inducible nitric oxide synthase (iNOS), has many important roles in inflammatory conditions. This study aimed to evaluate the anti-inflammatory effects of an iNOS-specific inhibitor, N-(3-(aminomethyl)benzyl)acetamidine (1400W), on experimentally induced rat pulpitis in the upper incisors of 6-wk-old male Wistar rats. 1400W (1 mg kg(-1)), the non-specific NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME, 50 mg kg(-1)), or sterile saline (control) were administered before the application of lipopolysaccharide (LPS). Rats were killed 3, 6, 9, 12, 24, 48, and 72 h after LPS application, and immunocompetent cells were detected immunohistochemically. The numbers of granulocytes infiltrating into the pulp were significantly depressed in the 1400W group compared with the saline and L-NAME groups. The kinetics of the macrophages and Ia(+) cells in the 1400W group were similar to those in the L-NAME group, while the maximum numbers in both groups were significantly reduced compared with those in the saline group. These results suggest that NO may be responsible for the infiltration of immunocompetent cells in the progress of pulpitis, and that 1400W is a promising candidate for controlling pulpal inflammatory reactions.