Action of GABAB receptor on local network oscillation in somatosensory cortex of oral part: focusing on NMDA receptor.

The balance of activity between glutamatergic and GABAergic networks is particularly important for oscillatory neural activities in the brain. Here, we investigated the roles of GABAB receptors in network oscillation in the oral somatosensory cortex (OSC), focusing on NMDA receptors. Neural oscillation at the frequency of 8-10 Hz was elicited in rat brain slices after caffeine application. Oscillations comprised a non-NMDA receptor-dependent initial phase and a later NMDA receptor-dependent oscillatory phase, with the oscillator located in the upper layer of the OSC. Baclofen was applied to investigate the actions of GABAB receptors. The later NMDA receptor-dependent oscillatory phase completely disappeared, but the initial phase did not. These results suggest that GABAB receptors mainly act on NMDA receptor, in which metabotropic actions of GABAB receptors may contribute to the attenuation of NMDA receptor activities. A regulatory system for network oscillation involving GABAB receptors may be present in the OSC.

Relationships between feeding behaviors and emotions: an electroencephalogram (EEG) frequency analysis study.

Feeding behaviors may be easily affected by emotions, both being based on brain activity; however, the relationships between them have not been explicitly defined. In this study, we investigated how emotional environments modulate subjective feelings, brain activity, and feeding behaviors. Electroencephalogram (EEG) recordings were obtained from healthy participants in conditions of virtual comfortable space (CS) and uncomfortable space (UCS) while eating chocolate, and the times required for eating it were measured. We found that the more participants tended to feel comfortable under the CS, the more it took time to eat in the UCS. However, the EEG emergence patterns in the two virtual spaces varied across the individuals. Upon focusing on the theta and low-beta bands, the strength of the mental condition and eating times were found to be guided by these frequency bands. The results determined that the theta and low-beta bands are likely important and relevant waves for feeding behaviors under emotional circumstances, following alterations in mental conditions.

Alternative strategy for driving voltage-oscillator in neocortex of rats.

Information integration in the brain requires functional connectivity between local neural networks. Here, we investigated the interregional coupling mechanism from the viewpoint of oscillations using optical recording methods. Low-frequency electrical stimulation of rat neocortical slices in a caffeine-containing medium induced oscillatory activity between the primary visual cortex (Oc1) and medial secondary visual cortex (Oc2M), in which the oscillation generator was located in the Oc2M and was triggered by a feedforward signal. During to-and-fro oscillatory activity, neural excitation was marked in layer II/III. When the upper layer was disrupted between Oc1 and Oc2M, feedforward signals could propagate through the deep layer and switch on the oscillator in the Oc2M. When the lower layer was disrupted between Oc1 and Oc2M, feedforward signals could propagate through the upper layer and switch on the oscillator in the Oc2M. In the backward direction, neither the upper layer cut nor the lower layer cut disrupted the propagation of the oscillations. In all cases, the horizontal and vertical pathways were used as needed. Fluctuations in the oscillatory waveforms of the local field potential at the upper and lower layers in the Oc2M were reversed, suggesting that the oscillation originated between the two layers. Thus, the neocortex may work as a safety device for interregional communications in an alternative way to drive voltage oscillators in the neocortex.

Study on structure-activity relationship of vitamin K derivatives: Conversion of the naphthoquinone part into another aromatic ring and evaluation of their neuronal differentiation-inducing activity.

We synthesized novel vitamin K derivatives by converting the naphthoquinone group to benzene derivatives and benzoquinone. We evaluated their neuronal differentiation activities to investigate the effect of the quinone moiety on this process. We observed that the 1,4-quinone as well as the side chain part play important roles in neuronal differentiation. We also performed QSAR analysis to predict the compounds which would have higher differentiation activity.

The fungal metabolite (+)-terrein abrogates osteoclast differentiation via suppression of the RANKL signaling pathway through NFATc1.

Pathophysiological bone resorption is commonly associated with periodontal disease and involves the excessive resorption of bone matrix by activated osteoclasts. Receptor activator of nuclear factor (NF)-κB ligand (RANKL) signaling pathways have been proposed as targets for inhibiting osteoclast differentiation and bone resorption. The fungal secondary metabolite (+)-terrein is a natural compound derived from Aspergillus terreus that has previously shown anti-interleukin-6 properties related to inflammatory bone resorption. However, its effects and molecular mechanism of action on osteoclastogenesis and bone resorption remain unclear. In the present study, we showed that 10 µM synthetic (+)-terrein inhibited RANKL-induced osteoclast formation and bone resorption in a dose-dependent manner and without cytotoxicity. RANKL-induced messenger RNA expression of osteoclast-specific markers including nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), the master regulator of osteoclastogenesis, cathepsin K, tartrate-resistant acid phosphatase (Trap) was completely inhibited by synthetic (+)-terrein treatment. Furthermore, synthetic (+)-terrein decreased RANKL-induced NFATc1 protein expression. This study revealed that synthetic (+)-terrein attenuated osteoclast formation and bone resorption by mediating RANKL signaling pathways, especially NFATc1, and indicated the potential effect of (+)-terrein on inflammatory bone resorption including periodontal disease.

Dynamics of Salivary Gland AQP5 under Normal and Pathologic Conditions.

AQP5 plays an important role in the salivary gland function. The mRNA and protein for aquaporin 5 (AQP5) are expressed in the acini from embryonic days E13-16 and E17-18, respectively and for entire postnatal days. Ligation-reopening of main excretory duct induces changes in the AQP5 level which would give an insight for mechanism of regeneration/self-duplication of acinar cells. The AQP5 level in the submandibular gland (SMG) decreases by chorda tympani denervation (CTD) via activation autophagosome, suggesting that its level in the SMG under normal condition is maintained by parasympathetic nerve. Isoproterenol (IPR), a ß-adrenergic agonist, raised the levels of membrane AQP5 protein and its mRNA in the parotid gland (PG), suggesting coupling of the AQP5 dynamic and amylase secretion-restoration cycle. In the PG, lipopolysaccharide (LPS) is shown to activate mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) signalings and potentially downregulate AQP5 expression via cross coupling of activator protein-1 (AP-1) and NF-κB. In most species, Ser-156 and Thr-259 of AQP5 are experimentally phosphorylated, which is enhanced by cAMP analogues and forskolin. cAMP-dependent phosphorylation of AQP5 does not seem to be markedly involved in regulation of its intracellular trafficking but seems to play a role in its constitutive expression and lateral diffusion in the cell membrane. Additionally, Ser-156 phosphorylation may be important for cancer development.

Good clinical teachers in pediatrics: The perspective of pediatricians in Japan.

BACKGROUND: The purpose of this study was to identify the attributes of good clinical teachers in pediatrics (CTPs) in Japan, and to elucidate pediatricians and pediatric trainees' perceptions of these attributes. METHODS: The attributes of good CTPs were identified qualitatively by conducting a thematic analysis of questionnaires answered by board-certified pediatricians and pediatric trainees. The attributes identified were rated quantitatively by a large number of participants in both groups. RESULTS: Forty-eight individual attributes of good CTPs were identified, which were classified into three domains: personal, pediatrician, and teacher. The three domains and most of the attributes were consistent with previous studies. However, a few additional attributes, including "is kind/thoughtful toward others" and "defends trainees", which may be unique to pediatricians in Japan, were identified. Significant differences in the pediatricians' and trainees' perceptions of these attributes were elucidated: The differences were most noticeable for teacher attributes and least for personal attributes. CONCLUSION: Although most of the identified attributes of good CTPs in our study appear to be universal, there were significant differences in the pediatricians' and trainees' perceptions of good CTPs, especially in relation to teacher attributes. Our study provides additional bases for good CTPs and future faculty development, for enhanced pediatric clinical education.

Antimony, a novel nerve poison, triggers neuronal autophagic death via reactive oxygen species-mediated inhibition of the protein kinase B/mammalian target of rapamycin pathway.

Antimony (Sb), a naturally occurring metal present in air and drinking water, has been found in the human brain, and there is evidence of its toxic effects on neurobehavioral perturbations, suggesting that Sb is a potential nerve poison. Here, we provide the first study on the molecular mechanism underlying Sb-associated neurotoxicity. Mice exposed to antimony potassium tartrate hydrate showed significantly increased neuronal apoptosis. In vitro, Sb triggered apoptosis in PC12 cells in a dose-dependent manner. Mechanically, Sb triggered autophagy as indicated by increased expression of microtubule-associated protein 1 light chain 3-II (LC3-II) and accumulation of green fluorescent protein-tagged LC3 dots. Moreover, Sb enhanced autophagic flux and sequestosome 1 (p62) degradation. Subsequent analyses showed that Sb treatment decreased phosphorylation of protein kinase B (Akt) as well as the mammalian target of rapamycin (mTOR), while an Akt activator protected PC12 cells from autophagy. Moreover, the antioxidant N-acetylcysteine attenuated Sb-induced Akt/mTOR inhibition and decreased autophagy and apoptosis, with autophagy inhibition also playing a cytoprotective role. In vivo, mice treated with Sb showed higher expression of LC3-II and p62 in the brain, consistent with the in vitro results. In summary, Sb induced autophagic cell death through reactive oxygen species-mediated inhibition of the Akt/mTOR pathway.

Enhancement of electroencephalogram activity in the theta-band range during unmatched olfactory-taste stimulation.

The aim of this study was to investigate how odor stimulation affects taste perception. Electroencephalogram (EEG) signals were measured from the frontal region of the head in normal, healthy subjects, and frequency analyses were performed. Each odor stimulation was delivered while the subject was tasting chocolate, using chocolate paste as the odorant for 'matched odor stimulation,' and garlic paste for 'unmatched odor stimulation.' Differences in EEG signals appeared between the matched and unmatched arms of the study. Comparison of the frequencies of EEGs captured under the condition of unmatched odor stimulation with those captured under the condition of matched odor stimulation showed that the occupancy rate of the theta-frequency band under the condition of unmatched odor stimulation was higher than that under the condition of matched odor stimulation. Interestingly, a negative correlation existed between the occupancy rate of the theta-frequency band and the subjective feeling of chocolate sweetness. The present findings suggest that when humans receive odors that do not match with the foods being consumed, subjective feelings are disturbed and theta-band brain activity is increased while the unmatched information is cross-checked.

Fungal metabolite (+)-terrein suppresses IL-6/sIL-6R-induced CSF1 secretion by inhibiting JAK1 phosphorylation in human gingival fibroblasts.

Control of bacterial infection-induced inflammatory responses is one of the effective therapeutic approaches of periodontal diseases. Natural products such as lipid mediators and metabolites from microorganisms have been used for decreasing inflammation. We previously reported that (+)-terrein inhibited activation of STAT3 and ERK1/2 in interleukin-6 (IL-6) signaling cascade, leading to prevent vascular endothelial growth factor (VEGF) secretion in human gingival fibroblasts (HGFs). However, little is still known about the role of (+)-terrein on inflammatory responses. In this study, we provided the possibility of novel action that (+)-terrein inhibits activation of Janus-activated kinase 1 (JAK1), which has a central function in IL-6 signaling cascade, and alters expression of mRNAs and proteins induced by IL-6/soluble IL-6 receptor (sIL-6R) stimulation in HGFs. First, we performed PCR array to examine IL-6/sIL-6R-induced mRNA expression, and then expression of mRNA and protein of colony stimulating factor-1 (CSF1) and VEGF were clearly determined by quantitative RT-PCR and ELISA, respectively. Treatment with (+)-terrein suppressed expression of mRNA and protein of CSF1 and VEGF by IL-6/sIL-6R stimulation. Next, to test the effect of (+)-terrein on IL-6/sIL-6R signaling cascade, we demonstrated whether (+)-terrein affects phosphorylation of JAK1 and its downstream proteins, Akt and SHP-2. Western blotting revealed that (+)-terrein inhibited IL-6/sIL-6R-induced phosphorylation of JAK1, Akt, and SHP-2. Therefore, (+)-terrein suppresses IL-6/sIL-6R-induced expression of CSF1 and VEGF via inhibition of JAK1, Akt, and SHP-2. Based on our results, we suggest that (+)-terrein is a candidate compound for anti-inflammatory effect associated with IL-6 signaling.

Effects of 3 months continuous intake of supplement containing Pantoea agglomerans LPS to maintain normal bloodstream in adults: Parallel double-blind randomized controlled study.

In this study, the effects on the maintenance of normal bloodstream by lipopolysaccharide (LPS) were investigated in the parallel-group randomized double-blind study using supplement containing Pantoea agglomerans LPS (201.5 µg/tablet as LPS). Screening was previously performed in the implementation of the study. Adult males and females with normal value to borderline (healthy subjects) in the hematologic parameters, for which reference values were given, were chosen in this study. The period of ingestion of the supplement was 3 months. As the result, a significant decrease in the rate of change (the ratio when the baseline was 1) of HbA1c, which is a glycative stress marker, was found in the group which ingested LPS supplement after 3 months. Also, a significant increase in the number of fingertip capillary vessels was found compared with the control group. From these results, the effects of the maintenance of bloodstream by ingestion of LPS were shown.

Reliability and acceptability of six station multiple mini-interviews: past-behavioural versus situational questions in postgraduate medical admission.

BACKGROUND: The multiple mini-interview (MMI) is increasingly used for postgraduate medical admissions and in undergraduate settings. MMIs use mostly Situational Questions (SQs) rather than Past-Behavioural Questions (PBQs). A previous study of MMIs in this setting, where PBQs and SQs were asked in the same order, reported that the reliability of PBQs was non-inferior to SQs and that SQs were more acceptable to candidates. The order in which the questions are asked may affect reliability and acceptability of an MMI. This study investigated the reliability of an MMI using both PBQs and SQs, minimising question order bias. Acceptability of PBQs and SQs was also assessed. METHODS: Forty candidates applying for a postgraduate medical admission for 2016-2017 were included; 24 examiners were used. The MMI consisted of six stations with one examiner per station; a PBQ and a SQ were asked at every station, and the order of questions was alternated between stations. Reliability was analysed for scores obtained for PBQs or SQs separately, and for both questions. A post-MMI survey was used to assess the acceptability of PBQs and SQs. RESULTS: The generalisability (G) coefficients for PBQs only, SQs only, and both questions were 0.87, 0.96, and 0.80, respectively. Decision studies suggested that a four-station MMI would also be sufficiently reliable (G-coefficients 0.82 and 0.94 for PBQs and SQs, respectively). In total, 83% of participants were satisfied with the MMI. In terms of face validity, PBQs were more acceptable than SQs for candidates (p = 0.01), but equally acceptable for examiners (88% vs. 83% positive responses for PBQs vs. SQs; p = 0.377). Candidates preferred PBQs to SQs when asked to choose one, though this difference was not significant (p = 0.081); examiners showed a clear preference for PBQs (p = 0.007). CONCLUSIONS: Reliability and acceptability of six-station MMI were good among 40 postgraduate candidates; modelling suggested that four stations would also be reliable. SQs were more reliable than PBQs. Candidates found PBQs more acceptable than SQs and examiners preferred PBQs when they had to choose between the two. Our findings suggest that it is better to ask both PBQs and SQs during an MMI to maximise acceptability.

Successful third renal transplantation in a child with an occluded inferior vena cava: A novel technique to use the venous interposition between the transplant renal vein and the infrahepatic inferior vena cava.

A girl aged 11 years and 3 months with occlusion of the inferior vena cava had experienced two renal transplant graft failures since birth. The third renal transplant from a live donor was carried out. Preoperative evaluation showed that the arteries from the right common to the right external iliac artery were absent, and the ilio-caval vein was occluded below the level of the renal vein. The donor's renal artery was anastomosed to the aorta. The donor's ovarian and large saphenous veins were used to extend the transplant renal vein to the recipient's patent inferior vena cava. The present report concludes that the extension of a short donor renal vein using other donor veins is a viable therapeutic option for pediatric patients with vascular occlusions.

Interplay between non-NMDA and NMDA receptor activation during oscillatory wave propagation: Analyses of caffeine-induced oscillations in the visual cortex of rats.

Generation and propagation of oscillatory activities in cortical networks are important features of the brain. However, many issues related to oscillatory phenomena are unclear. We previously reported neocortical oscillation following caffeine treatment of rat brain slices. Input to the primary visual cortex (Oc1) generates N-methyl-d-aspartate (NMDA) receptor-dependent oscillations, and we proposed that the oscillatory signals originate in the secondary visual cortex (Oc2). Because non-NMDA and NMDA receptors cooperate in synaptic transmission, non-NMDA receptors may also play an important role in oscillatory activities. Here we investigated how non-NMDA receptor activities contribute to NMDA receptor-dependent oscillations by using optical recording methods. After induction of stable oscillations with caffeine application, blockade of NMDA receptors abolished the late stable oscillatory phase, but elicited 'hidden' non-NMDA receptor-dependent oscillation during the early depolarizing phase. An interesting finding is that the origin of the non-NMDA receptor-dependent oscillation moved from the Oc1, during the early phase, toward the origin of the NMDA receptor-dependent oscillation that is fixed in the Oc2. In addition, the frequency of the non-NMDA receptor-dependent oscillation was higher than that of the NMDA receptor-dependent oscillation. Thus, in one course of spatiotemporal oscillatory activities, the relative balance in receptor activities between non-NMDA and NMDA receptors gradually changes, and this may be due to the different kinetics of the two receptor types. These results suggest that interplay between the two receptor types in the areas of Oc1 and Oc2 may play an important role in oscillatory signal communication.

Past-behavioural versus situational questions in a postgraduate admissions multiple mini-interview: a reliability and acceptability comparison.

BACKGROUND: The Multiple Mini-Interview (MMI) mostly uses 'Situational' Questions (SQs) as an interview format within a station, rather than 'Past-Behavioural' Questions (PBQs), which are most frequently adopted in traditional single-station personal interviews (SSPIs) for non-medical and medical selection. This study investigated reliability and acceptability of the postgraduate admissions MMI with PBQ and SQ interview formats within MMI stations. METHODS: Twenty-six Japanese medical graduates, first completed the two-year national obligatory initial postgraduate clinical training programme and then applied to three specialty training programmes - internal medicine, general surgery, and emergency medicine - in a Japanese teaching hospital, where they underwent the Accreditation Council for Graduate Medical Education (ACGME)-competency-based MMI. This MMI contained five stations, with two examiners per station. In each station, a PBQ, and then an SQ were asked consecutively. PBQ and SQ interview formats were not separated into two different stations, or the order of questioning of PBQs and SQs in individual stations was not changed due to lack of space and experienced examiners. Reliability was analysed for the scores of these two MMI question types. Candidates and examiners were surveyed on this experience. RESULTS: The PBQ and SQ formats had generalisability coefficients of 0.822 and 0.821, respectively. With one examiner per station, seven stations could produce a reliability of more than 0.80 in both PBQ and SQ formats. More than 60% of both candidates and examiners felt positive about the overall candidates' ability. All participants liked the fairness of this MMI when compared with the previously experienced SSPI. SQs were perceived more favourable by candidates; in contrast, PBQs were perceived more relevant by examiners. CONCLUSIONS: Both PBQs and SQs are equally reliable and acceptable as station interview formats in the postgraduate admissions MMI. However, the use of the two formats within the same station, and with a fixed order, is not the best to maximise its utility as an admission test. Future studies are required to evaluate how best the SQs and PBQs should be combined as station interview formats to enhance reliability, feasibility, acceptability and predictive validity of the MMI.

Successful treatment with mycophenolate mofetil and tacrolimus in juvenile severe lupus nephritis.

Lupus nephritis (LN) of juvenile onset often has severe disease presentation. Despite aggressive induction therapy, up to 20% of patients with LN are resistant to initial therapy and up to 44% suffer a renal relapse. However, there is no consensus on an appropriate therapeutic regimen for refractory LN. We report a 13-year-old girl with recurrent LN who was not taking her medications. At age of 11 years, she was diagnosed with LN classified as International Society of Nephrology/Renal Pathology Society (ISN/RPS) class IV G (A) + V. She was treated with prednisolone and MMF after nine methylprednisolone pulses. Nineteen months later, she was admitted to the hospital with generalized edema. Her symptoms were nephrotic syndrome and acute renal dysfunction. She received three methylprednisolone pulses for 3 days, followed by oral prednisolone and MMF. Twenty-seven days after the three methylprednisolone pulses, her acute renal dysfunction was improved, but the nephrotic syndrome was not improved. A second biopsy showed diffuse lupus nephritis classified as the predominant finding of ISN/RPS class V. We added tacrolimus to the MMF. Four months after adding tacrolimus, the nephrotic syndrome improved. We conclude that adding tacrolimus to the treatment regimen for LN resistant to MMF is effective.

Pantoea agglomerans lipopolysaccharide maintains bone density in premenopausal women: a randomized, double-blind, placebo-controlled trial.

Lipopolysaccharide fromPantoea agglomerans (LPSp) facilitates Ca and P turnover in chicken calvaria and femurs. This study investigated osteoporosis prevention by the oral administration of LPSp in mice and in double-blind clinical tests. Using ovariectomized (OVX) osteoporosis mice model, we investigated the effects of LPSp on the bone density and Ca concentration after ingesting LPSp-containing water for 4 weeks. Oral administration of LPSp tended to suppress the decline in the bone density and the cortical bone thickness in the OVX mice. Moreover, the Ca concentrations were maintained in the OVX-LPSp mice. The effects of LPSp on bone turnover were tested in randomized and double-blind clinical test subjects, who were healthy women aged 40-79 years. The subjects ingested either soy milk without LPSp (control group) or with LPSp (LPSp group) for 3 months. The results showed that the LPSp group on premenopause maintained their bone density compared with the control group pre- and postmenopause. Moreover, these effects were maintained for 2 months postobservation. LPSp maintains bone volume and density in vivo. Thus, a combination of soy milk and LPSp may be useful for osteoporosis prevention.

Influences of multiple tooth-loss on signal travel in the insular cortex of rats.

The insular cortex (IC) processes various kinds of sensory and emotional information. Multiple tooth-loss induces impairment of oral sensory and motor functions, which might result in the up- or down-regulation of signal processing in the IC. In the present study, we investigated how multiple tooth-loss affects neural activities in the IC. Slices of the IC were prepared from control (untreated) rats and rats raised following the loss of their upper molar teeth, and optical recordings with voltage-sensitive dye were made. Electrical stimulation was delivered to the agranular IC (AIC). The velocity of optical signal from the AIC to the granular IC (GIC) decreased in multiple tooth-loss rats compared with control rats. Field potentials from the GIC were recorded. Onset times of evoked response at the GIC recorded from multiple tooth-loss rats were prolonged compared with those recorded from control rats, suggesting that signal velocity in multiple tooth-loss rats had decreased. A reduced signal velocity was accompanied by neuronal loss in the GIC, which was confirmed by counting the cell numbers on Nissl-stained sections. Thus, multiple tooth-loss may have influences on the GIC where signal processing speed decreases.

Enhancement of oscillatory activity in the endopiriform nucleus of rats raised under abnormal oral conditions.

Endopiriform nucleus (EPN) is located deep to the piriform cortex, and has neural connections with not only neighboring sensory areas but also subcortical areas where emotional and nociceptive information is processed. Well-balanced oral condition might play an important role in stability of brain activities. When the oral condition is impaired, several areas in the brain might be affected. In the present study, we investigated whether abnormal conditions of oral region influence neural activities in the EPN. Orthodontic appliance that generates continuous force and chronic pain-related stress was fixed to maxillary incisors of rats, and raised. Field potential recordings were made from the EPN of brain slices. We previously reported that the EPN has an ability to generate membrane potential oscillation. In the present study, we have applied the same methods to assess activities of neuron clusters in the EPN. In the case of normal rats, stable field potential oscillations were induced in the EPN by application of low-frequency electrical stimulation under the medium with caffeine. In the case of rats with the orthodontic appliance, stable field potential oscillations were also induced, but both duration of oscillatory activities and wavelet number were increased. The enhanced oscillations were depressed by blockade of NMDA receptors. Thus, impairment of oral health under application of continuous orthodontic force and chronic pain-related stress enhanced neural activities in the EPN, in which up-regulation of NMDA receptors may be concerned. These findings suggest that the EPN might be involved in information processing with regard to abnormal conditions of oral region.

Effects of isoproterenol on aquaporin 5 levels in the parotid gland of mice in vivo.

In the membrane fraction of mouse parotid gland (PG), the protein level of aquaporin 5 (AQP5), a member of the water channel family, was increased by injection (ip) of isoproterenol (IPR), a ß-adrenergic agonist, at 1 h, and stayed at high levels until 6 h; this change occurred simultaneously as amylase secretion. The AQP5 level then decreased and returned toward the original level at 12-48 h. After IPR injection, the AQP5 mRNA gradually increased and reached a maximum at 24 h. The facts suggest a rapid appearance of AQP5 at plasma membrane by IPR and subsequent degradation/metabolism by activation of proteolytic systems. Pretreatment of animals with two calpain inhibitors, N-Ac-Leu-Leu-methininal (ALLM) and calpeptin, as well as a protein synthesis inhibitor, cycloheximide (CHX), significantly suppressed the IPR-induced AQP5 degradation in the PG membrane fraction; such suppression was not observed by two proteasome inhibitors, MG132 and lactacystin, or the lysosome denaturant chloroquine, although most of these inhibitors increased AQP5 protein levels in unstimulated mice. The AQP5 protein was also degraded by µ-calpain in vitro. Furthermore, we demonstrated that µ-calpain was colocalized with AQP5 in the acinar cells by immunohistochemistry, and its activity in the PG was increased at 6 h after IPR injection. These results suggest that the calpain system was responsible for IPR-induced AQP5 degradation in the parotid gland and that such a system was coupled to the secretory-restoration cycle of amylase in the PG.