Immunohistochemical demonstration of exocytosis-regulating proteins withinrat molar dentinal tubules

No morphologically defined synaptic structures have so far been detected be tween nerve terminals and the dentine-producing odontoblasts. Recent studie s of the molecular mechanisms in neuronal exocytosis have identified severa l proteins that participate in synaptic-vesicle exocytosis. By localizing t hese proteins with immunohistochemical methods, information about the capac ity for synaptic exocytosis should be obtained. Here, antibodies directed a gainst some of the exocytosis-related proteins were used to investigate whe ther they are present in nerve fibers within the dentinal tubules in rat mo lars. Antibodies against synaptosome-associated protein of 25 kDa, Rab 3, s ynaptotagmin and synapsin all produced a punctuate staining pattern, sugges ting that the proteins are accumulated in bouton-like elements. The results demonstrate that a set of exocytosis-related proteins is accumulated in th e dentinal tubules, most probably within the intradentinal nerves. This fin ding is consistent with the hypothesis that intradentinal nerves can mediat e efferent signals. (C) 1999 Elsevier Science Ltd. All rights reserved.