Dynamics of Carotid Sinus Elasticity During Pressor Reaction

Abstract

The volume-elasticity coefficient of the sinocarotid region, in vivo and in situ, in experiments on anesthetized dogs, was studied in the course of an induced pressor reaction in order to elucidate some controversial questions concerning the role of the distensibility of the sinus wall in the mechanisms of excitation of the sinocarotid receptors. The coefficient of volume-elasticity, calculated as pulse pressure/pulse volume ratio, was evaluated in relation to mean B.P., recorded simultaneously. Changes in the coefficient of elasticity of the sinocarotid region were found to precede compensation of the pressor reaction, viz., in the period of compensation the coefficient of elasticity of the sinocarotid wall--under otherwise equal physical conditions--was lower than in the period of rising pressure. The above-mentioned relations can be ascertained also after resection of the Hering nerve, i.e., after deafferentation and serious injury to the efferent innervation of the sinocarotid region. These changes are probably brought about by an automatic myogenic activity of smooth muscles of the vascular wall. The significance of the results obtained is pointed out in relation to the problems concerning the mechanism of excitation of the receptors of the sinocarotid region, especially with regard to the dependence of excitation of these receptors on distensibility (coefficient of elasticity) of the sinus wall.