Confocal immunofluorescence study of rat aortic body chemoreceptors and associated neurons in situ and in vitro.

Aortic bodies (ABs) are putative peripheral arterial chemoreceptors, distributed near the aortic arch. Though presumed to be analogous to the well-studied carotid bodies (CBs), their anatomical organization, innervation, and function are poorly understood. By using multilabel confocal immunofluorescence, we investigated the cellular organization, innervation, and neurochemistry of ABs in whole mounts of juvenile rat vagus and recurrent laryngeal (V-RL) nerves and in dissociated cell culture. Clusters of tyrosine hydroxylase-immunoreactive (TH-IR) glomus cells were routinely identified within these nerves. Unlike the CB, many neuronal cell bodies and processes, identified by peripherin (PR) and neurofilament/growth-associated protein (NF70/GAP-43) immunoreactivity, were closely associated with AB glomus clusters, especially near the V-RL bifurcation. Some neuronal cell bodies were immunopositive for P2X2 and P2X3 purinoceptor subunits, which were also found in nerve terminals surrounding glomus cells. Immunoreactivity against the vesicular acetylcholine transporter (VAChT) was detected in local neurons, glomus cells, and apposed nerve terminals. Few neurons were immunopositive for TH or neuronal nitric oxide synthase. A similar pattern of purinoceptor immunoreactivity was observed in tissue sections of adult rat V-RL nerves, except that glomus cells were weakly P2X3-IR. Dissociated monolayer cultures of juvenile rat V-RL nerves yielded TH-IR glomus clusters in intimate association with PR- or NF70/GAP-43-IR neurons and their processes, and glial fibrillary acidic protein-IR type II (sustentacular) cells. Cocultures survived for several days, wherein neurons expressed voltage-activated ionic currents and generated action potentials. Thus, this coculture model is attractive for investigating the role of glomus cells and local neurons in AB function.