Intraepithelial Vagal Sensory Nerve Terminals in Rat Pulmonary Neuroepithelial Bodies Express P2X3 Receptors

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Abstract
The neurotransmitters/modulators involved in the interaction between pulmonary neuroepithelial bodies (NEBs) and the vagal sensory component of their innervation have not yet been elucidated. Because P2X3 purinoreceptors are known to be strongly expressed in peripheral sensory neurons, the aim of the present study was to examine the localization of nerve endings expressing P2X3 purinoreceptors in the rat lung in general and those contacting pulmonary NEBs in particular. Most striking were intraepithelial arborizations of P2X3 purinoceptor–immunoreactive (IR) nerve terminals, which in all cases appeared to ramify between calcitonin gene–related peptide (CGRP)– or calbindin D28k (CB)–labeled NEB cells. However, not all NEBs received nerve endings expressing P2X3 receptors. Using CGRP and CB staining as markers for two different sensory components of the innervation of NEBs, it was revealed that P2X3 receptor and CB immunoreactivity were colocalized, whereas CGRP-IR fibers clearly formed a different populati...