Reflex responses of sympathetic preganglionic neurones initiated by different cardiovascular receptors in spinal animals

Abstract

We recorded the discharge of 66 single sympathetic preganglionic fibres isolated from the third and fourth left thoracic sympathetic rami communicantes of spinal vagotomized cats. Various mechanical and chemical stimuli were applied to different cardiovascular receptors in order to initiate reflex responses. Stimuli affecting mainly cardiac receptors always increased the discharge of the responsive fibres.Conversely, stimuli affecting simultaneously cardiac and vascular receptors or restricted to aortic receptors, either increased or decreased the discharge of the same fibres. The responses, consistent for each individual fibre, were reflex in nature. The data demonstrate that both specificity and convergence regulate cardiovascular sympathetic spinal reflexes.