Abstract
Effect of bradykinin (BK) on the release of met-enkephalin (ME) -like peptides from the rat incisor pulp was examined in in vitro experiments using whole pulp. BK dose-dependently increased the release of ME-like peptides and it was antagonized by Des-Arg9- [Leu8] -BK, a potent BK-antagonist. High K+ did not show any influence on the release. The BK effect was not influenced in Ca++-free medium. These findings suggested that effect of BK on the release of ME-like peptides from the pulp was mediated through B1-receptor and was Ca++-independent. In addition, the BK effect was not affected in presence of ouabain, suggesting that the release may be not active. Kyotorphin, an enkephalin releaser in central nervous system, also increased the content and the release of ME-like peptides in and from the pulp. Interestingly, the kyotorphin effect was attenuated by BK and vice versa. This fact may be explained as an interaction between BK and kyotorphin which may be different in mechanism of action. From the results in the present and the previous studies, the hypothesis that ME-like peptides in the pulp might control pain in a negative feedback mechanism was presented.
