Influence of Changes in Microcirculation on the Excitability of the Sensory Unit in the Tooth of the Cat

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Abstract
Simultaneous determinations of radioactive iodide disappearance rate (k‐value) and sensory nerve impulse frequency from dentinal cavities were performed on canine teeth of anesthetized cats. Changes in k‐value reflecting changes in pulpal microcirculation were obtained by direct sympathetic nerve stimulation or by thermal stimulation. Sympathetic nerve stimulation re duced the k‐value and induced an initial increase in nerve impulse frequency. During maximal sympathetic nerve stimulation this initial increase was followed by a marked depression in impulse frequency. Application of heat increased k‐value as well as impulse frequency, while cold reduced k‐value and induced an initial increase in nerve impulse frequency followed by a decrease. Thermal stimulation superimposed during maximal sympathetic stimulation, when k‐value was depressed, was inadequate to evoke an appreciable increase in sensory nerve in pulse frequency. It is suggested that the excitability of sensory units in the tooth is strongly modulated by changes in pulpal microcirculation induced by, for example, stimulation of sympathetic vasoconstrictor fibres.