Excitation of carotid body chemoreceptors by neuropeptide-Y.

Neuropeptide-Y (NPY) is a peptide co-localised with noradrenaline in many sympathetic nerves. Recently, it has been found in postganglionic sympathetic nerves running to blood vessels in the carotid body. When NPY is administered to cats by infusion into the arterial blood close to the carotid bodies, breathing is stimulated. This effect is abolished when the carotid sinus nerves are cut. Similar intra-carotid infusions of NPY can be demonstrated to increase the frequency of firing of chemoreceptor afferent nerves. However, NPY introduced into the blood vessels of the carotid body immediately prior to halting its blood flow does not modify the development of chemoreceptor discharge in response to developing asphyxia. The findings are consistent with NPY causing excitation of chemoreceptors by causing local vasoconstriction and stagnant asphyxia.