INTERACTION BETWEEN PAIN AND VASODILATION INTHE PULPITIS, IDENTIFICATION OF VASODILATOR SUBSTANCES

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(1) Histamine is a classical, but still interesting inflammatory mediator. Many people have long believed that histamine is derived from mast cells or basophils alone. However, the hidtamine forming enzyme, histidine decarboxylase (HDC), is induced in a variety of tissues in responses to gram-positive and gram-negative bacterial components and to various cytokines. HDC is induced even in mast-cell-deficient mice. The histamine newly formed via the induction of HDC is released immediately and may be involved in a variety of immune responses. We conclude that histamine can be produced via the induction of HDC by a mechanism coupled with cytokine network. We call this histamine neohistamine to distinguish it from the classical histamine derived from mast cells or basophils. Neohistamine is involved in physiological reactions, inflammation, immune responses and a variety of diseases such as pulpitis.(2) Dynamic changes in pulpal blood flow (PBF) in cat mandibular canine teeth were elicited by electrical stimulation of the distal cut end of IAN, at various levels of baseline blood flow (BBF), with blood flow monitored by Laser Doppler Flowmetry. The amplitude of the PBF vasodilator response increased as BBF was adjusted downwards (by cooling down the tooth). In contrast, the amplitude of the PBF vasoconstrictor response increased as the BBF level rose. Vasodilator responses could be transformed into vasoconstrictor responses, and vice versa, by alterations in the BBF level. No systemic blood pressure changes were elicited throughout the experiment. These results indicate that a consideration of baseline vascular tone is important whenever we discuss or calculate the size of PBF responses to various stimuli.