The carotid body chemoreceptor: an investigation in the mouse

The carotid body chemoreceptor has been investigated in the normal mouse and in the wobbler mutant. Electron microscopic studies show that the synaptic vesicle-containing nerve endings on type I cells are reduced in number in the mutant to 4.2% of the normal number. The function of the chemoreceptors was examined by recording ventilation and testing the response to different inspired gases and to the intra-arterial injection of cyanide. In addition recordings of chemoreceptor activity were made from the sinus nerve. No distinction could be drawn between the normal and the mutant mouse. No relationship was found between chemoreceptor activity and the respiratory cycle. If the synaptic vesicle-containing endings are afferent then only 4.2% of the normal number appear to be needed for normal function.