We investigated that localization of immunoreactivity and expression of mRNA for the γ-aminobutyric acid (GABA)_A receptor-γ 1 and GABA transporter-3 by immunohistochemistry and in situ hybridization in the rat submandibular gland. Further, we analyzed the role of GABA on salivary secretion. Both the GABA_A receptor and GABA transporter were expressed in the acinar, striated duct, collecting duct and submandibular ganglion cells. The expression of mRNA for the receptor and transporter was mainly localized in the submandibular ganglion. No salivary secretion was observed by GABA (10^-8-10^-33M) perfusion in the absence of electrical stimulation of chorda (20 Hz, 2-3 V, 5ms). GABA (10^-6-10^-3M)significantly inhibited chorda-evoked salivary secretion (the parasympathetic secretory response). This inhibition, which was induced by GABA, was antagonized by the GABA_A receptor antagonist, bicuculline (10^-3 and 10^-6M) and picrotoxin (10^-3 and 10^-5M). Inaddition, GABA inhibited the atropine-resistant parasympathetic secretory response. The GABA receptor antagonist picrotoxin (10^-3M)increased in the salivary flow with chorda stimulation at 1 Hz. On the other hand, salivary secretion evoked by electrical stimulation of the superior cervical ganglion (sympathetic secretory response) was not inhibited byGABA. Both functional and histochemical findings revealed that parasympathetic inhibitory regulation via GABA_A receptors is present in the rat submandibular gland.

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We studied the effects of cilostazol on diabetic and chronic constriction injury (CCI) neuropathy using the formalin test. Cilostazol increased blood flow to the nerves, and seemed to improve CCI and diabetic neuropathy by decreasing ischemia and hypoxia. Although flinching increased during all phases under CCI neuropathy, cilostazol caused a greater increase during phase Q than in other phases. CCI neuropathy may decrease the response of nociceptors. Although animals show self-nocifensor in phase Q, we did not find this in our study. Under diabetic neuropathy, flinching increased in phases 1 and Q. Cilostazol tended to suppress flinching in diabetic rats. Cilostazol may suppress activation of C fibers and substance P discharge. We found no significant changes in phase 2. Cilostazol may have no effect on inflammatory pain. The CCI model, which is related to causalgia, and the diabetic model, which is related to diabetic neuropathy, may be useful in future clinical studies.

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Thalidomide has a therapeutic effect if administered before neuropathic pain occurs, however, it has no effect if administered after. This was thought to result from the completed formation of a cytokine cascade. We investigated the possibility that neuropathic pain may be treated by the experimental administration of a large dose thalidomide after pain onset. We administered 200 mg・kg^-1, 100 mg・kg^-1, and 0 mg・kg^-1 of thalidomide to rats in which neuropathic pain had occurred due to CCI, and measured its effect on mechanoallodynia and cold-allodynia 7, 14, and 21 days after administration. We found that only the group that had received the 200 mg・kg^-1 of thalidomide showed an improvement in mechano-allodynia. This may have been caused by antiedema effect of thalidomide.

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We investigated ten cases of verruciform xanthoma of the oral mucosa clinically, histopathologically and immunohistochemically, and performed molecular biological examinations for human papillomavirus (HPV) infection. Foam (xanthoma) cells in the lamina propria are thought to be derived from macrophages. Epithelial proliferation caused by HPV infection as HPV 6 and 11 was detected in all cases examined. These results indicate that HPV infection initially causes papillary or verrucous epithelial proliferation and that secondarily foam cells form in the lamina propria owing to chronic irritation to the proliferating epithelium.

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Reticular fibers, which are almost completely type III collagen, form a scaffold for cell migration, whereas collagen fibers, which are type I collagen, are responsible for tissue support. To elucidate the role of reticular fibers in the wound healing process, we oberved tooth extraction sites in rats using the reticular silver impregnation technique, immunohistochemistry for type III collagen, and the rapid in situ hybridization (rapid ISH)method for the type III collagen gene. Type III collagen was found where the reticular fibers had been present. The expression of the type III collagen and the type III collagen gene was observed in the extraction wound after 3 days, but gradually decreased and disappeared by 14 days. Reticular fibers composed of type III collagen and the type III collagen gene were found during the granulation tissue stage of wound healing. During the process of wound healing after tooth extraction, reticular fibers were replaced with collagen fibers, and type III collagen disap-peared. These results indicate that bone is formed in the area where reticular fibers had been,and that the decreased production of type III collagen leads to the start of bone formation.

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Paclitaxel is an effective anti-cancer drug. However, it can induce peripheral neuropathy in humans. We investigated the occurrence of paclitaxel-induced neuropathy in humans and attempted to construct an animal model that could be used to elucidate the clinical symptoms of neuropathic pain as well as the mechanism of its occurrence. We administered paclitaxel directly to the left sciatic nerve in rats and carried out behavioral tests bilaterally every week for four weeks. Forty male Sprague-Dawley rats were divided into four groups of the each paclitaxel, another with cremophor EL, a third with physiological saline solution, and the last received paclitaxel injections in the muscle. The sciatic nerve of all of the rats was exposed, and enclosed in a neural silicon tube which was fitted with an internal silicon catheter. The catheter was connected to an osmotic pump secured in the peritoneal cavity. In the paclitaxel group, although cold allodynia was demonstrated in some rats, there was no mechano allodynia. The mechano hyperalgesia test, revealed that six of the ten rats did not have a hind paw withdrawal response. These effects developed only on the left side and there were no change on the right. No effects were seen in the other three groups. We feel that the paclitaxel model that we developed can be of value in future research on neuropathic pain.

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Although apoptosis is generally thought to be inhibited in malignant tumors,the phenomenon is not well understood in benign tumors. We used the terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL) method to study apoptosis in pleomorphic adenoma. We found an apoptosis-positive reaction in the nuclei of a few tumor cells that had tubuloductal structures, neoplastic cells in sheets, and myoepithelial cells made up of myxoid structures. More apoptosis-positive cells were found in luminal tumor cells of tubular and duct-like structures. In oral papillomas, some epithelial cells showed apoptosis-positive reactions in the nucleus, although very few positive cells were seen in the five cases of oral squamous cell carcinomas we examined. We concluded that apoptosis tends to occur in ductal epithelial cells in pleomorphic adenoma and that expression of apoptosis in the cells of benign tumors is different from that in malignant tumors such as cancer.

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Decorin, a small dermatan sulfate proteoglycan, is distributed throughout the extracellular matrix of periodontal tissues and is an important mediator of tissue development and repair. Previously, we demonstrated a significant increase in decorin mRNA expression in gingival tissue with chronic periodontal disease. Real-time reverse transcriptase-polymerase chain reaction (PCR) offers a rapid, sensitive method to quantify this substance. To elucidate the fluctuation of decorin mRNA during the process of inflammation,we examined its expression in cultured human gingival fibroblasts stimulated by inter-leukin (IL)-1β for 3 to 48 h using a real-time PCR detection system. Normal human periodontal fibroblasts were obtained from explant cultures of human gingiva. Total RNA was reverse-transcripted and amplified by real-time quantitative PCR to determine the mRNA level. TGF-β, type I collagen and IL-6 mRNA expression were also investigated. Decorin and collagen mRNA in fibroblasts stimulated by IL-1β was expressed weakly at 3 h, increased significantly at 8 and 24 h, and then gradually decreased at 48 h. TGF-β mRNA was also strongly expressed at 24 h. IL-6 mRNA levels apparently peak at 8 h, and were decreased at 24 and 48 h. There was a high correlation (r=0.8626) between decorin and TGF-β mRNA expression. These results indicate that gingival fibroblasts stimulated by IL-1β actively express IL-6 mRNA as an early event of inflammation, followed by decorin, collagen and TGF-β, which are associated with collagen fibrils, as a later event coexisting with destruction and repair.

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