The local effect of pH changes in the cerebrospinal fluid on the ventrolateral areas of medulla oblongata and on the spinal cord surface on the activity of cardiac and vertebral sympathetic nerves.

Application of acid cerebrospinal fluid at pH 6.8 to the ventral surface of the medulla oblongata in cats increased the arterial blood pressure and the activity of the vertebral nerve and enhanced respiratory modulation of the vertebral and cardiac nerves. Alkaline cerebrospinal fluid at pH 7.7 applied to the ventral surface of the medulla oblongata increased the arterial blood pressure without changes in the sympathetic nerve activity. When the spinal cord was superfussed with artificial acid cerebrospinal fluid at the Th1 level the activity of the vertebral nerve and cardiac nerve increased and the arterial blood pressure rose. The authors discuss the possibility of regulation of the activity of sympathetic neurons in the medulla and spinal cord by means of direct action of pH and pCO2 on the neurons, or through an indirect effect mediated by superficial chemoreceptors of the medulla oblongata. The role of local changes of the brain blood flow in the mechanism of these results is discussed as well.