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The present study investigated the morphological characteristics of subserosal afferent nerve endings with immunoreactivity for the P2X3 purinoceptor (P2X3) in the rat stomach by immunohistochemistry of whole‐mount preparations using confocal scanning laser microscopy. P2X3 immunoreactivity was observed in subserosal nerve endings proximal and lateral to the gastric sling muscles in the distal antrum of the lesser curvature. Parent axons ramified into several lamellar processes to form net‐like complex structures that extended two‐dimensionally in every direction on the surface of the longitudinal smooth muscle layer. The axon terminals in the periphery of P2X3‐immunoreactive net‐like structures were flat and looped or leaf‐like in shape. Some net‐like lamellar structures and their axon terminals with P2X3 immunoreactivity were also immunoreactive for P2X2. P2X3‐immunoreactive nerve fibers forming net‐like terminal structures were closely surrounded by S100B‐immunoreactive terminal Schwann cells, whereas axon terminals twined around these cells and extended club‐, knob‐, or thread‐like protrusions in the surrounding tissues. Furthermore, a retrograde tracing method using fast blue dye indicated that most of these nerve endings originated from the nodose ganglia of the vagus nerve. These results suggest that P2X3‐immunoreactive subserosal nerve endings have morphological characteristics of mechanoreceptors and contribute to sensation of a mechanical deformation of the distal antral wall associated with antral peristalsis. [ABSTRACT FROM AUTHOR]

ATP is the major excitatory transmitter from chemoreceptor type I cells to sensory nerve endings in the carotid body, and has been suggested to be released by exocytosis from these cells. We investigated the mRNA expression and immunohistochemical localization of vesicular nucleotide transporter (VNUT) in the rat carotid body. RT‐PCR detected mRNA expression of VNUT in extracts of the tissue. Immunoreactivity for VNUT was localized in a part of type I cells immunoreactive for synaptophysin (SYN), but not in glial‐like type II cells immunoreactive for S100 and S100B. Among SYN‐immunoreactive type I cells, VNUT immunoreactivity was selectively localized in the sub‐population of tyrosine hydroxylase (TH)‐immunorective type I cells associated with nerve endings immunoreactive for the P2X3 purinoceptor; however, it was not detected in the sub‐population of type I cells immunoreactive for dopamine beta‐hydroxylase. Multi‐immunolabeling for VNUT, P2X3, and Bassoon revealed that Bassoon‐immunoreactive products were localized in type I cells with VNUT immunoreactivity, and accumulated on the contact side of P2X3‐immunoreactive nerve endings. These results revealed the selective localization of VNUT in the subpopulation of TH‐immunoreactive type I cells attached to sensory nerve endings and suggested that these cells release ATP by exocytosis for chemosensory transmission in the carotid body. [ABSTRACT FROM AUTHOR]