Search

The present study investigated the localization and the adenosine 5′-triphosphate (ATP)-degrading function of the plasma membrane-bound ecto-nucleotidase, ectonucleoside triphosphate diphosphohydrolase 2 (NTPDase2), in the rat adrenal medulla. The effect of ATP degradation product, adenosine 5′-diphosphate (ADP), on carbachol (CCh)-induced intracellular Ca2+ ([Ca2+]i) responses in adrenal chromaffin cells was examined using calcium imaging. NTPDase2-immunoreactive cells were distributed between chromaffin cells. NTPDase2-immunoreactive cells were immunoreactive for glial fibrillary acidic protein and S100B, suggesting that they were sustentacular cells. NTPDase2-immunoreactive cells surrounded chromaffin cells immunoreactive for vesicular nucleotide transporter and P2Y12 ADP-selective purinoceptors. In ATP bioluminescence assays using adrenal medullary slices, ATP was rapidly degraded and its degradation was attenuated by the NTPDase inhibitors sodium polyoxotungstate (POM-1) and 6- N, N -diethyl- d -β,γ-dibromomethylene ATP (ARL67156). ADP inhibited CCh-induced [Ca2+]i increases of chromaffin cells in adrenal medullary slices. The inhibition of CCh-induced [Ca2+]i increases by ADP was blocked by the P2Y12 purinoceptor antagonist AZD1283. CCh-induced [Ca2+]i increases were also inhibited by the P2Y1, P2Y12, and P2Y13 purinoceptor agonist 2-methylthioadenosine diphosphate trisodium (2MeSADP), in combination with the P2Y1 purinoceptor antagonist MRS2179. These results suggest that sustentacular cells express NTPDase2 to degrade ATP released from adrenal chromaffin cells, and ADP modulates the excitability of chromaffin cells via P2Y12 purinoceptors to regulate catecholamine release during preganglionic sympathetic stimuli. (J Histochem Cytochem 72: 41–60, 2024) [ABSTRACT FROM AUTHOR]

The present study investigated the cellular components and afferent innervations of taste buds in the rat incisive papilla by immunohistochemistry using confocal scanning laser microscopy. Taste buds containing guanine nucleotide‐binding protein G(t), subunit α3 (GNAT3)‐imunoreactive cells were densely distributed in the lateral wall of incisive papilla forming the opening of nasoincisor ducts. GNAT3‐immunoreactive cells in the taste buds were slender in shape and the tips of apical processes gathered at one point at the surface of the epithelium. The number of taste buds was 56.8 ± 4.5 in the incisive papilla. The incisive taste buds also contained ectonucleoside triphosphate diphosphohydrolase 2‐immunoreactive cells and synaptotagmin‐1‐immunoreactive cells in addition to GNAT3‐immunoreactive cells. Furthermore, GNAT3‐immunoreactive cells were immunoreactive to taste transduction molecules such as phospholipase C, β2‐subunit, and inositol 1,4,5‐trisphosphate receptor, type 3. P2X3‐immunoreactive subepithelial nerve fibers intruded into the taste buds and terminated with hederiform or calix‐like nerve endings attached to GNAT3‐immunoreactive cells and synaptosomal‐associated protein, 25 kDa‐immunoreactive cells. Some P2X3‐immunoreactive endings were also weakly immunoreactive for P2X2. Furthermore, a retrograde tracing method using fast blue dye indicated that most of the P2X3‐immunoreactive nerve endings originated from the geniculate ganglia (GG) of the facial nerve. These results suggest that incisive taste buds are morphologically and cellularly homologous to lingual taste buds and are innervated by P2X3‐immunoreactive nerve endings derived from the GG. The incisive papilla may be the palatal taste papilla that transmits chemosensory information in the oral cavity to the GG via P2X3‐immunoreactive afferent nerve endings. [ABSTRACT FROM AUTHOR]

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]