Immunohistochemical approach to examine baroreceptor morphology

Arterial baroreceptors play a very important role in the regulation of the cardiopulmonary system. However, information on the morphology of these sensors at a single sensory unit level is limited. Much less is known about receptor structure as a whole than the structures at the sub‐cellular level, due to ineffective methods for light microscopy. In the current study, we describe an immunohistochemical approach to reveal the structure of these important receptors. The aortic arches were obtained from the rabbit. These tissues were reacted with antibodies against Na + /K + ‐ATPase, then fluorescently labeled, and examined with a confocal microscope. Sensory receptor structures were most often identified in the aortic arch near the bifurcation or origin of the common carotid and subclavian arteries. These sensory receptors were present in compact clusters, similar to bunches of grapes. Morphologically, receptor terminals, similar to those in airway slowly adapting stretch receptors, swell to form leaf‐like or knob‐like expansions. A single myelinated axon may connect with multiple receptor structures. In other words, receptor structures formed a network. In summary, our approach provides excellent detailed structure of the baroreceptor and provides the opportunity to explore chemical compositions of the sensory receptor. Certainly, it will facilitate our understanding of baroreceptor function.