No abstract

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 netlike 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 S100Bimmunoreactive 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.

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.

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 synaptosomalassociated 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.

5-hydroxytriptamine (5-HT: serotonin) is an important transmitter that causes vessel constriction, although few studies have examined the effect of 5-HT on venous smooth muscles. The intracellular Ca 2+ concentration ([Ca 2+ ] i ) plays an essential role in stimulus-response coupling in numerous tissue/cells including vascular smooth muscle cells. The present study was performed to examine whether differences between arteries and veins in the response to 5-HT can be detected under confocal microscope with respect to [Ca 2+ ] i dynamics. In posterior ciliary arteries of rats, 5-HT induced a [Ca 2+ ] i increase. The 5-HT-induced responses were caused by both Ca 2+ influx and mobilization. Agonist and antagonist experiments revealed that arterial smooth muscles possess 5-HT 1a, 1b, 2 (Gprotein-coupled type) and 5-HT 3 (ion channel type) receptors, and that 5-HT 2 in particular plays a major role in these responses. For vorticose veins, the 5-HT-induced responses were also caused by both Ca 2+ influx and mobilization. However, the cAMP dependent pathway (5-HT 4-7 ) was found to be significant in vasocontraction with respect to 5-HT in these vessels. Thus, Ca 2+ mobilization was induced by 5-HT 2 and 5-HT 4-7 in a vessel-dependent manner, whereas Ca 2+ influx universally was induced by 5-HT 3 . These results indicate that the posterior ciliary arteries and vorticose veins in the same tissue might differ greatly in their responses to stimulus.Retinal vein occlusion is the second most common retinal vascular disorder after diabetic retinopathy and is considered to be an important cause of visual impairment (9, 54). Ischemic disorders of the optic nerve constitute an important cause of visual loss (7, 30). For example, ischemic optic neuropathy, an acute disorder of the optic nerve, is now known to be a common yet serious vision-threatening disease in middle-aged and elderly populations (13,72). Similarly, evidence is mounting that vascular insufficiency in the intraorbital portion of the optic nerve might play an important role in amorose glaucomatous optic neuropathy and papilloedema (65, 83). The main vascular sources of the intraorbital portion of the optic nerve consist of the branches of the posterior ciliary artery and the central retinal artery (29,36,50,79). The choroid blood vessels of the eye provide 80-95% of the blood to the ocular structures including the outer retina and ciliary processes (6). The central retinal artery supplies the optic nerve and the inner retina, while the posterior ciliary artery pierces the sclera to enter the choroidal coat of the eye. The central retinal artery ends without significant anastomoses (32). The choroidal vessels are innervated by sympathetic and parasympathetic nerves; the parasympathetic innervation of the choroid derives from the ipsilateral pterygopalatine ganglion (59). Parasympathetic nerve stimulation produces nitric oxide-mediated vasodilation, which