Rat Parotid Gland Research Articles

Expression and functional regulation of the nuclear receptors AHR, PXR, and CAR, and the transcription factor Nrf2 in rat parotid gland.

Nuclear receptors and transcription factors regulate the functions of many genes involved in cellular physiology and pathology (e.g. tumorigenesis and autoimmune diseases). The present study was performed to define the expression and the regulation of aryl hydrocarbon receptor (AhR), pregnane X receptor (PXR), constitutive androstane receptor (CAR), and nuclear factor E2-related factor 2 (Nrf2) in the rat parotid gland. Constitutive expression, as well as expression after stimulation with specific inducers for AhR [2,3,7,8-tetrachloro-dibenzylo-p-dioxin (TCDD)], Nrf2(oltipraz), PXR (dexamethasone), and CAR (phenobarbital), was evaluated using the quantitative PCR. Cellular localization of the nuclear receptors and the transcription factor was visualized by immunohistochemical staining. The study revealed constitutive expression of AhR as well as Nrf2, and their induction by TCDD andoltipraz, respectively. Immunohistochemical analysis revealed constitutive, predominantly cytoplasmic, expression of the AhR receptor, especially in interlobular striated duct cells, with nuclear shift upon exposure to TCDD. Inducible expression of Nfr2 was found mainly in the cytoplasm of intralobular striated duct cells. Constitutive expression of PXR and CAR was not found. Bearing in mind the involvement of AhR and Nrf2 in the regulation of many genes, it seems that these factors may play also a role in salivary gland physiology and pathology.

Nifedipine-induced histological changes in the parotid glands of hypertensive rats.

Nifedipine is a widely used anti-anginal and anti-hypertensive agent. It is associated with significant gingival changes attributed more to collagen hyperplasia than to enhancement of protein synthesis. We investigated the influence of nifedipine on morphological changes in the parotid glands of rats in a model of hypertension. Twenty-eight male Wistar rats (8-10 weeks; 200±15 g) were divided into four groups (A-D). Hypertension was induced by surgical means in groups C and D. Animals in groups B and D were treated with nifedipine (0.85 mg/kg) via a gastroesophageal catheter the day after surgery (experimental day-1) for 2 weeks. A significant difference was observed between the control group and nifedipine group and between the control group and hypertension group with regard to the weight of the parotid gland and its surface area. Histological findings demonstrated changes in the parotid glands of hypertensive animals with mild vessel dilatation and infiltration of inflammatory cells. These histological findings seemed to be due more to changes in venous function than to alterations in gland architecture.

Effects of menopause and diabetes on the rat parotid glands: A histopathological and stereological study

Background: The menopause is a physiological process that occurs and diabetes is a metabolic disease that has an increased incidence in advancing age in women. Aims & Objective: The purpose of the study to examine the effect of menopause and/or diabetes that causes pathophysiological status on parotid gland. Materials and Methods: Sprague-dawley 24 adult female rats (12 week old) were randomly, six rats in each group, divided into four groups; non-diabetic healthy (control), Diabetic (DM) group, Ovariectomized (OVX) group, Post Ovariectomy-Diabetes Induced (DM+OVX) group, respectively. To evaluate the results histopathological, histochemical and stereological analyses were performed. Results: Degenerative acini and duct cells with increased cytoplasmic lipid accumulation (vacuolization) in DM groups, polymorph nuclear infiltrations in OVX groups and extensive swollen nucleus with karyorrhexis and increased cytoplasmic lipid accumulation in serous acinus cells in DM+OVX group were detected. Furthermore the changes in the amount and character of secretion especially DM and DM+OVX groups and hypertrophic changes in the acinus epithelium in DM and/or the OVX groups were distinguished. Conclusion: The results revealed the effects of diabetes and ovariectomy on the cellular changes and pathophysiological processes of these changes in parotid glands. These findings may highlight to other pathophysiological processes of the role of the salivary glands associated with the pathogenesis due to diabetes and menopause. Additionally, correlated molecular mechanism of pathophysiological processes of DM and/or OVX on parotid gland, suggested further investigation.

Partial Purification and Characterization of the Rat Parotid Gland Protein Kinase Catalyzing Phosphorylation of Matured Destrin at Ser-2

Destrin, also called actin-depolymerizing factor (ADF), exists in resting parotid tissue as phosphorylated (inactive) and dephosphorylated (active) forms, and β-adrenergic stimulation of this tissue induces dephosphorylation of destrin. It is suggested that destrin dephosphorylation is involved in cortical F-actin disruption observed in parallel with β-agonist-induced amylase secretion. At present, the phosphorylation/dephosphorylation mechanism of destrin in parotid tissue is not known. We previously detected, in a crude rat parotid extract, a constitutively active protein kinase catalyzing phosphorylation of destrin; however, its identification has been hampered by difficulty in its enrichment. The purpose of this study was to explore a simple purification method(s) for this enzyme. To this end, we first developed a high-throughput dot-blot assay for the kinase with an anti-phosphodestrin antibody and then studied its purification by column chromatography on several media. We found that the kinase could be partially purified by sequential chromatography on DEAE-cellulose, phenyl-Sepharose, and hydroxyapatite columns. In each chromatography, however, the kinase could be eluted, at the cost of resolution, only by sharp increases in the elution power of the eluent; gradual increases in the elution power resulted in unacceptably poor recovery. We confirmed that enzymatic properties of the kinase were not basically altered during the purification. Further purification of the kinase was achieved by native polyacrylamide gel electrophoresis (PAGE), which resolved the kinase activity into two bands and separated the activity from most proteins (the kinase activity after PAGE was detected with destrin-coated polyvinylidene difluoride membranes and the anti-phosphodestrin antibody). The two bands seem to constitute the major destrin-phosphorylating activity in the resting rat parotid gland. We here report its partial purification and characterization together with the detection methods.

구속 스트레스에 대한 백서 타액선의 Apo Taq 발현

본 연구에서는 백서에 구속 스트레스를 통하여 정서적인 스트레스를 가한 후, 이하선 조직의 형태학적 변화 양상을 광학 현미경으로 관찰하였으며, 타액선 조직에서 세포자멸사의 평가는 TUNEL assay에 양성을 보이는 세포 수를 측정하여, 각 군별 차이를 비교하여 다음과 같은 결과를 얻었다. 1. 백서 이하선에서 구속 스트레스를 가한 후, 5일부터 타액선 선포의 위축 및 농염이 관찰되었으며, 7일부터 세포자멸사소견이 관찰되기 시작하였다. 2. In situ DNA end labelling assay를 통하여 TUNEL 염색을 시행한 결과, 타액선 장액선포에서 양성세포가 구속 스트레스에 대해 5일부터 통계학적으로 유의하게 증가하여 7일째에 가장 큰 지수를 보여 조직학적 소견과 일치하였다. 따라서 구속에 의한 스트레스 증가에 따라 생체 내 타액선조직에서 세포자멸사가 유도됨을 증명할 수 있었으며, 향후 유도 신호전달 기전에 관한 연구가 이루어져야 한다고 사료된다. On this study, we treated rats with restraint stress, and observed the changes with an optical microscope. Within the salivary gland tissue, we measured cell apoptosis cycle evaluation which show positive reaction on TUNEL assay, and compared within the groups. For this study, 18 rats were divided into 3 groups; 1) 2 rats of group I were selected as a normal control. 2) 2 rats of group II, as a experimental control were placed in the restraint cone for 2 hours 3) 14 rats of group III were placed in the restraint cone for 2 hours once a day. The rats were sacrificed immediately (group II, as a experimental control), 1, 2, 3, 4, 5, 6 and 7days after application of the stress and the both parotid glands were excised. The conclusions follow. 1. 5 days after giving an confining stress to the parotid gland of Rats, we can observe the hypotropy and pus and inflammation of Rat parotid gland acinar cells, and after 7 days, we can see a cell apoptosis. 2. Through the In situ DNA end labeling assay and TUNEL dye, on serous glands, benign tumor cell increased with statistically significant result after 5 days from confining stress. And the index shows maximum value on 7th days, which is same result with histological opinion. Therefore, our study shows that a cell apoptosis can be induced by restraint stress on salivary gland tissue, and we think more study should be accomplished about the cell signaling pathway in the future.

The antipsychotic amisulpride: ultrastructural evidence of its secretory activity in salivary glands

Amisulpride is reported to inhibit clozapine-induced sialorrhea. Preclinically, clozapine evokes muscarinic-M1-type-mediated secretion that, however, amisulpride does not reduce. Instead, amisulpride, without causing any overt secretion per se, enhances both nerve- and autonomimetic-evoked salivation by unknown mechanism(s). Hypothesizing that amisulpride prepares the gland for secretion, we looked for ultrastructural events indicating secretory activity in intercellular canaliculi of serous/seromucous cells, that is, density increase in protrusions (reflecting anchored granules) and in microbuds (reflecting recycling membranes and/or vesicle secretion) and decrease in microvilli (reflecting the cytoskeletal re-arrangement related to exocytosis). Rat parotid and submandibular glands were exposed to amisulpride in vivo or in vitro. Glands were processed for transmission electron and scanning electron microscopy and then morphometrically assessed. Cells were packed with secretory granules. The density of protrusions increased in both glands, whereas significant and parallel changes in microvilli and microbuds occurred only in parotid glands, and in vitro. Amisulpride induced ultrastructural signs of secretory activity but to varying extent; in submandibular glands, in contrast to parotid glands, changes were not brought beyond the granular anchoring stage. Amisulpride may provide an overall readiness for secretion that will result in augmented responses to agonists, a phenomenon of potential interest in dry-mouth treatment.

The effect of fluoxetine on the structure of adult rat parotid glands and the possible role of pilocarpine with nizatidine

IntroductionHyposalivation is an important clinical side effect related to the use of antidepressants. Fluoxetine hydrochloride is a selective serotonin reuptake inhibitor used in the treatment of depression and anxiety disorders. Nizatidine, an H2 blocker, has a saliva stimulatory effect.Aim of the

Adaptive Parotid Gland Hypertrophy Induced by Dietary Treatment of GSE in Rats

In a 13-week feeding toxicity study of grape skin extract (GSE) performed previously, 5.0% GSE showed diffuse hypertrophy and basophilia in rat parotid glands. To clarify whether the change in the parotid glands was an adverse effect of GSE, 6-week-old male F344 rats were fed a diet containing 5.0% GSE or were administered a dose corresponding to the dietary concentration via gavage for 4 weeks, and the treatment was stopped for 2 weeks. To ascertain the effect of astringency, other animals were fed a diet containing 5.0% tannic acid (TA) using the same protocol as the GSE feed group. Control groups were fed a basal diet or were administered sterilized distilled water by gavage. In the GSE and TA feed groups, diffuse severe hypertrophy and basophilia in the parotid glandular epithelial cells were observed. Macroscopic, microscopic, and ultrastructural characteristics consistent with cellular hypertrophy was less apparent after the recovery period in both feed groups. In contrast, no changes were observed in the parotid glands of the gavage GSE and control groups at week 4. Based on these findings of parotid hypertrophy without cytotoxicity, the data from this and previous studies suggest that hypertrophy of the parotid glands induced by feeding treatment with GSE is an adaptive non-adverse effect that is reversible upon removal of the sialotrophic agent.

Antioxidant profile of salivary glands in high fat diet‐induced insulin resistance rats

There is no study analyzing the salivary antioxidant profile in the course of the insulin resistance. Rats were divided into two groups. One group was fed with a normal diet, another one with a high fat diet for 5weeks. The analysis included: catalase (CAT), superoxide dismutase, peroxidase activities, uric acid, and total antioxidant status concentrations. The activity of peroxidase in both kind of glands of insulin resistance rats was significantly reduced than in the control rats. The protein concentration, total amount of total antioxidant status in the parotid glands of insulin resistance rats were significantly lower than in the control glands The total amount of superoxide dismutase, CAT, and uric acid in the parotid glands of insulin resistance rats were significantly elevated in comparison with the control rats. The median values of the total amount of superoxide dismutase, CAT, peroxidase, total antioxidant status were significantly higher in the parotid than in the submandibular glands of the insulin resistance and control rats. Parotid and submandibular glands of rats react differently when exposed to insulin resistance condition; however, the parotid glands seem to be more affected. The main source of antioxidants is parotid glands of rats.

Efeitos do Ruído de Baixa Frequência de Alta Amplitude no Tecido Conjuntivo Perivasculo-Ductal da Glândula Parótida

In tissues and organs exposed to large pressure amplitude low frequency noise fibrosis occurs in the absence of inflammatory signs, which is thought to be a protective response. In the parotid gland the perivasculo-ductal connective tissue surrounds arteries, veins and the ductal tree. Perivasculo-ductal connective tissue is believed to function as a mechanical stabilizer of the glandular tissue. In order to quantify the proliferation of perivasculo-ductal connective tissue in large pressure amplitude low frequency noise-exposed rats we used sixty Wistar rats which were equally divided into 6 groups. One group kept in silence, and the remaining five exposed to continuous large pressure amplitude low frequency noise: g1-168h (1 week); g2-504h (3 weeks); g3-840h (5 weeks); g4-1512h (9 weeks); and g5-2184h (13 weeks). After exposure, parotid glands were removed and the perivasculo-ductal connective tissue area was measured in all groups. We applied ANOVA statistical analysis, using SPSS 13.0. The global trend is an increase in the average perivasculo-ductal connective tissue areas, that develops linearly and significantly with large pressure amplitude low frequency noise exposure time (p < 0.001). It has been suggested that the biological response to large pressure amplitude low frequency noise exposure is associated with the need to maintain structural integrity. The structural reinforcement would be achieved by increased perivasculo-ductal connective tissue. Hence, these results show that in response to large pressure amplitude low frequency noise exposure, rat parotid glands increase their perivasculo-ductal connective tissue.

Radioprotective Effect of Vitamin E in Parotid Glands: a Morphometric Analysis in Rats

The aim of this study was to evaluate the radioprotective effect of vitamin E on rat parotid glands by morphometric analysis. Sixty male rats were divided into 5 groups (n=6): control, in which animals received olive oil solution; olive oil/irradiated, in which animals received olive oil and were irradiated with a dose of 15 Gy of gamma radiation; irradiated, in which animals were irradiated with a dose of 15 Gy gamma radiation; vitamin E, which received α-tocopherol acetate solution; vitamin E/irradiated, which received α-tocopherol acetate solution before irradiation with a dose of 15 Gy gamma rays. Half of the animals were euthanized at 8 h, and the remaining at 30 days after irradiation. Both parotid glands were surgically removed and morphometric analysis of acinar cells was performed. Data were subjected to two-way ANOVA and Tukey's test (α=0.05). Morphometric analysis showed a significant reduction in the number of parotid acinar cells at 30 days in olive oil/irradiated and irradiated groups. In groups evaluated over time a significant reduction was shown at 30 days in olive oil/irradiated and irradiated groups, indicating that ionizing radiation caused tissue damage. The vitamin E/irradiated group presented more acinar cells than the irradiated group, but no statistically significant difference was observed (p>0.05). In conclusion, vitamin E seems to have failed as a radioprotective agent on acinar cells in rat parotid glands.

SU‐E‐T‐679: Implications of Radiobiological Bath and Shower Effects On Brainstem Dose Tolerance

Purpose: To gain insight into radiosurgical brainstem dose tolerance by considering the radiobiological implications of the bath and shower experiments. Methods: Clinical brainstem dose tolerance for radiosurgery is compared to the two extreme cases of hypofractionated whole brain irradiation and trigeminal neuralgia radiosurgery. In 2003 and 2009, experimental results were published wherein a low dose to a large volume (bath) was combined with a high dose to a small volume (shower), for the cases of rat cervical spinal cord and rat parotid gland. Clinically the uniqueness of each patients' tumor requires a customized mixture of bath and shower doses to the adjacent critical structures, whereas in the animal experiments it was possible to systematically vary the bath dose and the shower dose and to statistically analyze the outcomes to study the interactions in detail, although human response may differ. Results: Hypofractionated whole brain irradiation results in essentially uniform bath dose to the brainstem at a single fraction dose equivalent of about 10Gy, according to the LQ model. For radiosurgery, Timmerman's 2008 limit allows 1cc of brainstem to exceed 10Gy in a single fraction. Therefore since the volume of brainstem receiving the bath dose is reduced, it allows a higher shower dose to be received by a small volume, and the corresponding TG101 limit allows a max dose of 15Gy. In the case of trigeminal neuralgia, the bath dose to brainstem is much lower, and some institutions have allowed an extremely high shower dose of 45Gy in a single fraction to the maximum point dose in brainstem, with surprisingly infrequent side effects under conditions of meticulous targeting and dosimetric accuracy. Conclusion: Clinically the tradeoff between doses to large and small volumes is already implicitly taken into account, but comparison to the radiobiological research can help provide insight. Dr. Grimm developed and holds intellectual property rights to the DVH Evaluator software tool which is an FDA‐cleared product in commercial use

Isoproterenol stimulates transient SNAP23–VAMP2 interaction in rat parotid glands

The exocytosis of salivary proteins is mainly regulated by cAMP, although soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), which mediate cAMP-dependent exocytic membrane fusion, have remained unidentified. Here we examined the effect of isoproterenol (ISO) and cytochalasin D (CyD) on the level of SNARE complexes in rat parotid glands. When SNARE complexes were immunoprecipitated by anti-SNAP23, the coprecipitation of VAMP2 was significantly increased in response to ISO and/or CyD, although the coprecipitation of VAMP8 or syntaxin 4 was scarcely augmented. These results suggest that the SNAP23–VAMP2 interaction plays a key role in cAMP-mediated exocytosis from parotid glands. Structured summary of protein interactionsSnap23physically interacts with Vamp8, Vamp3 and Syn-4 by anti bait coimmunoprecipitation (View Interaction: 1, 2, 3)Vamp2physically interacts with Syn-4, Syn-3 and Snap23 by anti bait coimmunoprecipitation (View interaction)Syn-3physically interacts with Snap23 by anti bait coimmunoprecipitation (View interaction)Vamp2physically interacts with Snap23 and Syn-4 by anti bait coimmunoprecipitation (View interaction)Snap23physically interacts with Vamp8, Syn-4 and Vamp2 by anti bait coimmunoprecipitation (View interaction: 1, 2)

Effects of Single Exposure of Sodium Fluoride on Lipid Peroxidation and Antioxidant Enzymes in Salivary Glands of Rats

Many studies suggest that fluoride exposure can inhibit the activity of various enzymes and can generate free radicals, which interfere with antioxidant defence mechanisms in living systems. To further the understanding of this issue, this present study examined the effects of low-dose fluoride treatment on the activity of enzymatic antioxidant superoxide dismutase (SOD) and catalase (CAT), as well as the levels of lipid peroxidation (LPO) in the parotid (PA) and submandibular (SM) salivary glands of rats. Rats were injected with a single dose of sodium fluoride (NaF) (15 mg F−/kg b.w.) then euthanized at various time intervals up to 24 hours (h) following exposure. NaF exposure did not cause significant differences in SOD or CAT activity or LPO levels in PA glands compared to control. Conversely, SM glands presented increased SOD activity after 3 h and decreased SOD activity after 1, 12, and 24 h, while LPO was increased after 6, 12, and 24 h of the NaF injection. There were no significant differences in the CAT activity in the groups studied. Our results demonstrated that NaF intoxication caused oxidative stress in salivary glands few hours after administration. These changes were more pronounced in SM than in PA gland.

Ultrastructural study of the adult albino rat parotid gland with special reference to the role of stromal telocytes

Ultrastructural study of the adult albino rat parotid gland with special reference to the role of stromal telocytes

Isoproterenol modulates matrix metalloproteinase-2 (MMP-2) and its tissue inhibitor-2 (TIMP-2) in rat parotid gland

ObjectiveChronic isoproterenol treatment causes hypertrophy and hyperplasia of rodent salivary glands. Cell-extracellular matrix interactions play a critical role in salivary gland proliferation and matrix metalloproteinases (MMPs) are known to be involved in cell proliferation. The present study was undertaken to investigate the expression of MMP-2 and the tissue inhibitor metalloproteinase (TIMP)-2 in rat parotid gland following isoproterenol treatment. DesignFemale Wistar rats were daily treated with isoproterenol (25mg/kg body weight) for 0, 1, 3, and 7 days. Expression of parotid gland MMP-2 and its tissue inhibitor TIMP-2 was analysed by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. ResultsOur results suggest that isoproterenol modulates expression of MMP-2 and TIMP-2 mRNAs, as well as their protein expression levels in a time dependent-manner. Interestingly, at day 1 of treatment, MMP-2 and TIMP-2 expression were higher in comparison to untreated gland. At days 3 and 7, we can observe a gradual decrease of mRNA and protein levels of MMP-2 and TIMP-2. ConclusionsOur results suggest the presence of a isoproterenol-dependent modulation of extracellular matrix components. Such a modulation seems to be associated with β-adrenergic agonist-induced hyperplasy, occurring during the first 24h of agonist treatment, and hypertrophy of the parotid gland.

Effects of shock waves on oxidative stress in parotid gland of rat

This study was designed to investigate whether extracorporeal shock wave lithotripsy (ESWL) exposure to parotid gland produces an oxidative stress in parotid glands of rats. Twelve male Wistar-albino rats, 6 months of age with an average body weight of 250-300 g, were divided randomly into two groups, each consisting of six rats. The animals in the first group did not receive any treatment and served as control. The left parotid glands of animals in group 2 (ESWL treated) received a thousand 18 kV shock waves after anesthetizing the rats with 50 mg/kg of ketamine. The animals in both groups were killed 72 hours after the ESWL treatment, and the parotid glands were harvested for the determination of lipid peroxidation product malondialdehyde (MDA), antioxidant glutathione (GSH) levels and the activities of antioxidant enzymes such as superoxide dismutase (SOD), GSH-Px and catalase (CAT). It was found that MDA level increased in parotid glands of rats after the ESWL treatment. The SOD, GSH-Px and CAT enzyme activities, and the level of antioxidant GSH decreased in parotid gland of rats after the ESWL treatment. It was concluded that short-term ESWL treatment caused an increase in the free radical production and a decrease in the antioxidant enzyme activity in parotid glands of ESWL-treated rats.

Involvement of apoptosis and proliferation of acinar cells in atrophy of rat parotid glands induced by liquid diet

Parotid glands of experimental animals fed a liquid diet are reported to show atrophy (Hall and Schneyer 1964; Wilborn and Schneyer 1970; Hand and Ho 1981; Scott et al. 1990; Scott and Gunn 1991). To clarify whether apoptosis and proliferation of acinar cells participate in atrophy of rat parotid glands induced by liquid diet, rats were fed a liquid diet and compared to pellet-fed controls. Parotid glands were removed at 3, 7, 14 or 21 days, weighed, and examined using transmission electron microscopy (TEM), and studied immunohistochemically for cleaved-caspase-3 (Casp-3), a marker of apoptotic cells, and 5-bromo-2'-deoxyuridine (BrdU), a marker for proliferating cells. Body weights of experimental rats fed liquid diets were not significantly different from controls fed pellet diets; however weights of experimental parotid glands were smaller than those of controls. In the experimental parotid glands, structures like apoptotic bodies were histologically observed in acini at each time point; more Casp-3-positive acinar cells were identified in experimental parotid glands than in the controls on days 3, 7, and 14. Experimental glands showed fewer BrdU-positive acinar cells at each time point. TEM confirmed typical apoptotic acinar cells in the atrophic glands. These findings suggest that increased acinar cell apoptosis and reduced acinar cell proliferation occur in atrophic parotid glands of rats fed a liquid diet.

The Role of Estrogen on Rat Parotid Gland after Menopause

Objective: To determine the histopathological changes of estrogen deficiency and estrogen replacement treatment in parotid gland of ovariectomized rats. Method: Female albino rats were divided into 3 groups: sham, ovariectomized, and ovariectomized with estrogen replacement. Histopathological evaluation of rat parotid glands were done by using the diameter of acinus and striated duct (SD), height of SD, and interacinar connective tissue thickness. Apoptosis in parotid gland were examined by TUNEL staining. Results: Except interacinar connective tissue thickness, there were no significant differences between the sham-operated control and ovariectomized group in terms of the diameter of acinus and striated duct (SD) and height of SD. Estrogen replacement resulted in significant increase in the height of SD and interacinar connective tissue thickness. Apoptotic index was higher in both ovariectomized and estrogen replacement group compared to sham-operated control. Conclusion: Although estrogen replacement did not reduce apoptotic index in parotid gland of overiectomized rat, it may have some positive influence on saliva secretion by increasing interaciner connective tissue thickness.

Influence of experimental periodontitis on cholinergic stimulation of K+ release in rat parotid glands

In a rat model of experimental periodontitis it was investigated whether the presence of the inflammatory disease induced changes in carbachol-induced fluid secretion in parotid glands, by monitoring potassium release. The potency of carbachol, to induce K⁺ release, was higher in parotid glands from rats with experimental periodontitis. The antagonist with higher affinity for M₃ muscarinic acetyl-choline receptor subtype, 4-DAMP (selectivity: M₁=M₃), was more potent in inhibiting K⁺ release in periodontitis rats while the antagonist with a muscarinic M₁-receptor-selective profile (selectivity: M₁>M₃), pirenzepine, was more potent in control rats. Competition binding assays showed that both, M₁ and M₃ muscarinic acetyl-choline receptor subtypes are expressed in membranes of parotid glands. The K(i) of 4-DAMP was decreased in parotid glands from rats with experimental periodontitis while the Ki of pirenzepine was increased. The effect of periodontitis was reverted by the inhibition of the cyclooxygenase activity through indomethacin treatment (100 mg/k ip, 4 days). It was concluded that periodontitis could induce changes in muscarinic acetyl-choline receptor subtypes expression with a preferential increase of M₃ subtype, resulting in increased K⁺ released in response to carbachol and in a greater potency of 4-DAMP. These findings agree with the fact that a decrease of fluid secretion is not a condition of patients with periodontal disease.