Multifocal animated imaging of changes in cellular oxygen and calcium concentrations and membrane potential within the intact adult mouse carotidbody ex vivo

Carotid body (CB) type Icell hypoxia-sensing function is assumed to be based on potassiumchannel inhibition. Subsequent membrane depolarization initiates anintracellular calcium increase followed by transmitter release forexcitation of synapses with linked nerve endings. Several reports,however, contradict this generally accepted concept by showing thattype I cell oxygen-sensing properties vary significantly depending onthe method of their isolation. We report therefore for the first timenoninvasive mapping of the oxygen-sensing properties of type I cellswithin the intact adult mouse CB ex vivo by using multifocal Nipkowdisk-based imaging of oxygen-, calcium- and potential-sensitive cellulardyes. Characteristic type I cell clusters were identified in thecompact tissue by immunohistochemistry because of their large cellnuclei combined with positive tyrosine hydroxylase staining. Thecellular calcium concentrations in these cell clusters either increasedor decreased in response to reduced tissue oxygen concentrations.Under control conditions, cellular potential oscillations were uniformat ~0.02 Hz. Under hypoxia-induced membrane depolarization, theseoscillations ceased. Simultaneous increases and decreases in potentialof these cell clusters resulted from spontaneous burstlike activitieslasting ~1.5 s. type I cells, identified during the experiments bycluster formation in combination with large cell nuclei, seem torespond to hypoxia with heterogeneous kinetics.