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High blood pressure is a major risk factor of cerebro-cardiovascular outcomes. Blood pressure is partly regulated by the autonomic nervous system and its reflex functions, therefore, we hypothesized that pharmacological intervention in the brainstem that can regulate blood pressure could be a novel therapeutic strategy to control hypertension. We infused a group II metabotropic glutamate receptor (mGluR) antagonist (LY341495, 0.40 μg/day), using a mini-osmotic pump, into the dorsal medulla oblongata in young spontaneously hypertensive rats (SHRs), as this area is adjacent to the nucleus tractus solitarius (NTS), of which the neurons are involved in baroreflex pathways with glutamatergic transmission. Blood pressure was recorded for conscious rats with the tail cuff method. A 6-week antagonist treatment from 6 to 12 weeks of age slightly but significantly increased systolic blood pressure by &gt, 30 mmHg, compared to that in SHRs without treatment. Moreover, the effect continued even 3 weeks after the treatment ended, and concurred with an increase in blood catecholamine concentration. However, heart rate variability analysis revealed that LY341495 treatment had little effect on autonomic activity. Meanwhile, mRNA expression level of mGluR subtype 2, but not subtype 3 in the brainstem was significantly enhanced by the antagonist treatment in SHRs, possibly compensating the lack of mGluR signaling. In conclusion, mGluR2 signaling in the dorsal brainstem is crucial for preventing the worsening of hypertension over a relatively long period in SHRs, through a mechanism of catecholamine secretion. This may be a specific drug target for hypertension therapy.

The senescence-accelerated mouse (SAM) strain has been established as an inbred strain with an accelerated aging phenotype. SAM prone-8 (SAMP8), one of the SAM strain, exhibits learning disability, immune deficiency, and circadian rhythm loss at a relatively young age. However, it has not been clarified whether aging affects the autonomic nervous activity in SAMP8. The aim of this study was to clarify the utility of SAMP8 in age-related studies of autonomic nervous function. Electrocardiogram (ECG), body temperature, and locomotor activity were recorded to evaluate bio-behavioral activities. Autonomic nervous activity was evaluated via power spectral analysis of heart rate variability from ECG recordings. SAMP8 significantly decreased both biological and autonomic nervous functions, and the animals exhibited circadian rhythm loss of locomotive activity at as early as 40 weeks of age compared with a control strain at the same age. We concluded that the SAMP8 strain can be used as an animal model for age-related studies of autonomic nervous function.

Baroreflex dysfunction is partly implicated in hypertension and one responsible region is the dorsal medulla oblongata including the nucleus tractus solitarius (NTS). NTS neurons receive and project glutamatergic inputs to subsequently regulate blood pressure, while G-protein-coupled metabotropic glutamate receptors (mGluRs) play a modulatory role for glutamatergic transmission in baroreflex pathways. Stimulating group II mGluR subtype 2 and 3 (mGluR2/3) in the brainstem can decrease blood pressure and sympathetic nervous activity. Here, we hypothesized that the chronic stimulation of mGluR2/3 in the dorsal medulla oblongata can alleviate hypertensive development via the modulation of autonomic nervous activity in young, spontaneously hypertensive rats (SHRs). Compared with that in the sham control group, chronic LY379268 application (mGluR2/3 agonist; 0.40 μg/day) to the dorsal medulla oblongata for 6 weeks reduced the progression of hypertension in 6-week-old SHRs as indicated by the 40 mmHg reduction in systolic blood pressure and promoted their parasympathetic nervous activity as evidenced by the heart rate variability. No differences in blood catecholamine levels or any echocardiographic indices were found between the two groups. The improvement of reflex bradycardia, a baroreflex function, appeared after chronic LY379268 application. The mRNA expression level of mGluR2, but not mGluR3, in the dorsal medulla oblongata was substantially reduced in SHRs compared to that of the control strain. In conclusion, mGluR2/3 signaling might be responsible for hypertension development in SHRs, and modulating mGluR2/3 expression/stimulation in the dorsal brainstem could be a novel therapeutic strategy for hypertension via increasing the parasympathetic activity.

Cardiotoxicity is a concern in the development of microtubule-disassembling agents (MDAs) as vascular-disrupting agents of tumors. This study investigated cardiotoxicity in rats induced by a single-dose of combretastatin A4 disodium phosphate (CA4DP), an MDA and discussed the use of this rat model in nonclinical studies of MDAs. First, CA4DP (120 mg/kg) was administered to rats intravenously, and cardiac histopathology and blood biomarkers were examined after 0.5, 24, and 72 h. Next, CA4DP (120 mg/kg) was administered to rats intravenously, and the electrocardiography and echocardiography results were analyzed. The results showed that at 0.5 h after dosing, plasma creatine kinase (CK), CK-muscle/brain (CK-MB), and fatty acid binding protein 3 levels increased. At 24 h, lactate dehydrogenase (LDH)-1, CK, and CK-MB levels increased, and multifocal vacuolar degeneration of myocardial cells was observed in the apical inner layer. At 72 h, LDH-1 levels were increased, and multifocal myocardial necrosis was observed in the interventricular septum and inner layer of the apex of left ventricular wall. Furthermore, at 0.5 h, heart rate (HR), ejection fraction (EF), and cardiac output (CO) decreased. At 24 h, CO decreased. Finally, at 72 h, HR, EF, and CO decreased, and depression of the T-wave amplitude was observed. In conclusion, myocardial injury, bradycardia, and depressed cardiac function were induced in rats by a single-dose of CA4DP. The lesion distribution and electrocardiographic features suggested that myocardial injury was induced by ischemia. These findings are similar to MDA-induced cardiotoxicity in humans, and this rat model will prove useful in studies of the cardiotoxicity in humans.

Environmental enrichment (EE) can reduce anxiety and stress in experimental animals, while little is known about the influence on autonomic nervous activity especially in disease animal models. Diabetes mellitus (DM) is associated with cardiovascular autonomic dysfunction, which can be characterized by a higher resting heart rate and a lower heart rate variability (HRV). We hypothesized that EE can enhance parasympathetic nervous activity while reducing disease progression in type 2 diabetic mice. A telemetry transmitter was implanted in NSY mice to continuously record electrocardiograms (ECG). Animals were kept in a cage with or without a nest box as EE. The autonomic nervous activity was evaluated using power spectral analysis of HRV. Four weeks of EE could increase high frequency (HF) power, but no change was observed in the absence of EE. Although animals showed impaired glucose tolerance at 48 weeks of age regardless of EE, a worsen case was observed in control. These results indicate that EE can be necessary for long-term housing of experimental animals and may reduce the risk of impaired glucose tolerance in NSY mice by enhancing parasympathetic nervous activity. In future, it is demanded whether increasing parasympathetic nervous activity, whatever the method is, can prevent diabetes from worsening.

Because we found that WTC rats might be resistant to streptozotocin (STZ), we have elucidated the mechanisms of resistant to the diabetogenic effects of STZ in the WTC rats. Dose response to STZ was evaluated with glucose levels. No significant changes in glucose level to STZ administration were observed in WTC rats. Insulin secretion by suppling glucose was preserved in WTC rats even after STZ administration. Although there was no significant difference in gene expression of both GLUT2 and Kir6.2, which were involved in STZ resistance, between WTC rats and Wistar rats, the expression of metallothionein 2a in pancreas and liver to STZ administration of WTC rats was significantly higher than that of Wistar rats. Moreover, alloxan did not induce diabetes in WTC rats as same as STZ. These results suggest that WTC rats might have powerful antioxidant property to protect β cells in pancreas. Because the STZ-resistant property is very close characteristics to human beings, WTC rats will become a useful animal model in diabetic researches., Highlights • WTC rat was highly resistant to STZ. Insulin secretion by suppling glucose was preserved in WTC rats even after STZ administration. • No significant difference was observed in both GLUT2 and Kir6.2 expression between WTC and Wistar rats. • These results suggest that WTC rat might have powerful antioxidant property to protect bets cells in pancreas..

N-Acetyl-D-mannosamine (ManNAc), a precursor of a sialic acid, is recently reported to improve the cognitive function in aged animals. However, the effect of chronic administration of ManNAc on impaired synaptic transmission and plasticity with age still remain unknown. In this study, we electrophysiologically determined the effect of chronic administration of ManNAc on deteriorated synaptic transmission and plasticity using hippocampal slices from senescence-accelerated mouse prone 8 (SAMP8) which shows age-related impairment of learning and memory. Oral administration of ManNAc for 8 weeks improved the field excitatory postsynaptic potentials (fEPSPs) in both SAMP8 and SAM resistant 1 (SAMR1), the control strain of SAMP8, at 14 months of age, but not at 6 months of age. On the other hand, ManNAc administration improved long-term potentiation (LTP), representative of long-term synaptic plasticity, of 6 month-old SAMP8 but not of age-matched SAMR1. In addition, ManNAc improved LTP of 14 month-old SAMR1 but not of age-matched SAMP8. At the same time, we checked the PPR but ManNAc did not affect the PPRs at either before or after high-frequency stimulation for LTP induction. These results indicate that chronic administration of ManNAc improves the age-dependent attenuation of synaptic transmission and LTP, and shows the availability of ManNAc treatment as potential therapeutic application for cognitive dysfunction.

Aging is associated with a variety of physiological changes originating peripherally and centrally, including within the autonomic nervous system. Sleep-wake disturbances constitute reliable hallmarks of aging in several animal species and humans. Recent studies have been interested in N-acetylmannosamine (ManNAc) a potential therapeutic agent for improving quality of life, as well as preventing age-related cognitive decline. In this study, ManNAc (5.0 mg/ml) was administered in the drinking water of middle-aged male C57BL/6J mice (55 weeks old) for 7 days. Mice were housed under a 12:12 h light:dark cycle at 23-24 °C. We evaluated bio-behavioral activity using electrocardiogram, body temperature and locomotor activity recorded by an implanted telemetry transmitter. To estimate sleep-wake profile, surface electroencephalogram and electromyogram leads connected to a telemetry transmitter were also implanted in mice. Autonomic nervous activity was evaluated using power spectral analysis of heart rate variability. ManNAc-treated mice spent more time in a wakeful state and less time in slow wave sleep during the dark phase. Parasympathetic nervous activity was increased following ManNAc treatment, then the sympatho-vagal balance was shifted predominance of parasympathetic nervous system. Furthermore, improvement in sleep-wake pattern was associated with increased parasympathetic nervous activity. These results suggest that ManNAc treatment can improve bio-behavioral activity and sleep-wake quality in middle-aged mice. This may have implications for improving sleep patterns in elderly humans.

Systemic oxidative stress is considered to cause aging. In this study, to estimate the oxidative stress level in senescence-accelerated mouse prone 8 (SAMP8), we evaluated serum reactive oxygen species production and reduction capacity by measurement of Diacron-Reactive Oxygen Metabolites (d-ROM) and Biological Antioxidant Potential (BAP), respectively, with age. SAMP8 showed earlier increase of d-ROM value with age than SAM resistant 1 (SAMR1), the control strain. The BAP level was the highest in adult SAMP8, whereas SAMR1 presented the sustained BAP values between ages. These results indicate that oxidative stress in SAMP8 is higher than SAMR1. Our study is the first detailed report about d-ROM and BAP in SAMP8 and will provide useful fundamental data for future aging studies.

Cardiac ryanodine receptor gene (RyR2) mutations cause fatal arrhythmogenic diseases such as catecholaminergic polymorphic ventricular tachycardia and arrhythmogenic right ventricular cardiomyopathy. The N-terminal region of RyR2 is one of the hot spots for mutations. In this study, we investigated cardiac phenotypes of a knock-in mouse model carrying R420W mutation of RyR2. The N-terminal R420W mutation has already been found in juvenile sudden death cadavers of unrelated families. The depolarization-induced Ca(2+) transient amplitude was significantly lower in cardiomyocytes from RyR2(R420W/R420W) mice compared with wild-type mice. The time to peak of the Ca(2+) transient was significantly increased in RyR2(R420W/R420W) mice. Furthermore, the prolonged decay time from the peak of the Ca(2+) transient was detected in RyR2(R420W/R420W) mice. ECG telemetry revealed that various types of arrhythmias were induced in RyR2(R420W/R420W) mice in response to administration of caffeine and adrenaline. The mutant mice showed high occurrences of arrhythmias in response to heart stimulants compared with wild-type mice. These findings suggest that R420W mutation impairs depolarization-induced Ca(2+) oscillation in cardiomyocytes, which possibly results in sudden death due to stress-induced arrhythmias.

Aims Dilated cardiomyopathy (DCM) is characterized by ventricular dilation associated with systolic dysfunction, which could be caused by mutations in lamina/C gene ( LMNA ). LMNA -linked DCM is severe in males in both human patients and a knock-in mouse model carrying a homozygous p.H222P mutation ( Lmna H222P/H222P). The aim of this study was to investigate the molecular mechanisms underlying the gender difference of LMNA -linked DCM. Methods and results A whole-exome analysis of a multiplex family with DCM exhibiting the gender difference revealed a DCM-linked LMNA mutation, p.R225X. Immunohistochemical analyses of neonatal rat cardiomyocytes expressing mutant LMNA constructs and heart samples from the LMNA -linked DCM patients and Lmna H222P/H222P mice demonstrated a nuclear accumulation of androgen receptor (AR) and its co-activators, serum response factor, and four-and-a-half LIM protein-2. Role of sex hormones in the gender difference was investigated in vivo using the Lmna H222P/H222P mice, where male and female mice were castrated and ovariectomized, respectively, or treated with testosterone or an antagonist of AR. Examination of the mice by echocardiography, followed by the analyses of histological changes and gene/protein expression profiles in the hearts, confirmed the involvement of testicular hormone in the disease progression and enhanced cardiac remodelling in the Lmna H222P/H222P mice. Conclusion These observations indicated that nuclear accumulation of AR was associated with the gender difference in LMNA -linked DCM.

This study was conducted to clarify and reevaluate the cardiac and autonomic nervous effects of T-2 toxin, which had been previously examined by several acute experiments, in unrestrained and conscious rats implanted with telemetric transmitters. Two groups of rats were given two subcutaneous injections of 0.1 and 0.5 mg/kg of T-2 toxin with an interval of 3 days. Two other groups of rat were pre-implanted with osmotic minipumps by which atropine (20 mg/kg/day) or propranolol (100 mg/kg/day) was continuously administered preceding subcutaneous injection of T-2 toxin (0.5 mg/kg). The present study demonstrated that T-2 toxin caused marked arrhythmias, such as second-degree atrioventricular (AV) block, sinus bradycardia, supraventricular extrasystole, and ventricular extrasystole, which were accompanied by a significant increase in heart rate and a significant decrease in total power and low- and high-frequency power of heart rate variability, during 3 days of observation after the toxin administration. However, the occurrence of arrhythmia with conduction disturbance such as second-degree atrioventricular blocks was markedly diminished by pretreatment with atropine, while the occurrence of ventricular extrasystole was augmented by atropine. The present study with the telemetric measurement elucidated and confirmed that T-2 toxin produced significant cardiac dysfunctions involving disturbance of the conduction pathway influenced by the autonomic nervous activity and also possible direct effects on cardiac myocytes.

Cholinergic anti-inflammatory pathway (CAP) inhibits unrestrained inflammatory response in a variety of experimental models. Limited research has been done yet to examine the mechanisms of activating CAP on bio-behavioral changes such as heart rate (HR), blood pressure (BP), body temperature (BT), locomotor activity (LA), and autonomic nervous activity (ANA). We observed these parameters using telemetry to clarify pathophysiological mechanisms of CAP. Nicotine significantly attenuated LPS-induced changes in HR, BP, LA, and ANA. These changes were accompanied by significant inhibition of TNF-α and IL-1β syntheses. However the LPS-induced physiological responses persisted much longer than the cytokines production. These results indicate that systemic nicotine treatment inhibits LPS-induced cytokines production and attenuates the associated physiological and behavioral sickness responses.

Delayed rectifier potassium currents such as I (Kr) and I (Ks) play an important role in the repolarization phase of the action potential in cardiac myocytes. Electrophysiological studies have shown that the pig is a useful animal not only for clinical use as a good candidate for humans, but also for basic research in heart function or arrhythmia. However, no studies concerning the potassium channels on a molecular level have been done. To elucidate the expression level and distribution of delayed rectifier potassium channels in pigs, we quantitatively investigated the I (Kr) and I (Ks) channel subunits using the real-time polymerase chain reaction (PCR) method. The hearts from Clawn miniature pigs were separated into the apical and basal regions, and subsequently excised into transmural trisections within each of the left ventricular walls, epicardium, midcardium, and endocardium. After RNA extraction from these sites, real-time PCR was executed with reverse transcriptional products for quantitative analysis. The expression level of KCNE1 was significantly higher than those of KCNQ1, KCNH2, and KCNE2, which were comparable in all sites. Transmural heterogeneity of these potassium channel subunits was not detected on the mRNA level. These results indicate that KCNE1 is a dominant subunit on the post-transcriptional level in the miniature pig.

Although the effect of taurine on the heart and liver is well studied, there has been no direct observation concerning the effect of taurine on spatial learning and memory at the behavior level. In this study, we tested the effect of subacute taurine supplementation with evaluation by the Morris water maze method. Although swim distance to find the platform of taurine-supplemented rats was significantly longer than that of control rats due to increase of swimming velocity, escape latency and the efficacy of learning and memory was comparable in both groups. These results suggest that taurine supplemented orally does not affect the learning and memory function.

The KCNQ1 gene encodes a voltage-dependent potassium ion channel, and mutations in this gene are the most common cause of congenital long QT syndrome (LQTS). In the present study, we investigated the various phenotypic characteristics of vertigo 2 Jackson (C3H/HeJCrl-Kcnq1(vtg-2J)/J) mice with a Kcnq1 mutation. Both heterozygotes (vtg-2J/+) and homozygotes (vtg-2J/vtg-2J) showed prolonged QT intervals in electrocardiograms (ECGs) compared to C3H/HeJ control (+/+) mice. Furthermore, vtg-2J/vtg-2J mice showed gastric achlorhydria associated with elevation of their serum gastrin levels. The serum corticosterone levels were also significantly increased in vtg-2J/vtg-2J mice. In addition, vtg-2J/vtg-2J mice exhibited significantly higher blood pressure. These findings indicate that the Kcnq1 mutation in vtg-2J mice alters various physiological functions in the cardiac, gastric and adrenocortical systems, and suggest that vtg-2J mice may represent a useful model for studying Kcnq1 functions.

We explored the role of the transcription factor c-Fos in lipopolysaccharide (LPS)-induced cytokine response using mice lacking c-Fos (Fos-/- mice). Compared with wild-type controls, Fos-/- macrophages and mice showed significantly enhanced production of tumour necrosis factor (TNF)-alpha, interleukin (IL)-6 and IL-12 p40, but reduced production of the anti-inflammatory cytokine IL-10. Bandshift analysis revealed that LPS-induced NF-kappaB binding activity to a functional site in the TNF-alpha promoter was significantly higher in Fos-/- than in wild-type macrophages. Using telemetry, we monitored body temperature and heart rate after LPS injection and found that Fos-/- mice undergo more severe hypothermia and bradycardia than wild-type mice. Such shock responses in Fos-/- mice were significantly reversed by neutralizing TNF-alpha. These data reveal a novel in vivo role for c-Fos as an anti-inflammatory transcription factor acting through suppression of NF-kappaB activity.

Objective— We investigated the effects of fluvastatin on hypoxia-induced (1 to 3 weeks, 10% O 2 ) pulmonary hypertension with focus on endothelial nitric oxide synthase (eNOS) activity. Methods and Results— Oral fluvastatin treatment (1 mg/kg daily) prevented the causing and progression of pulmonary hypertension as determined by the right ventricular pressure, right ventricular hypertrophy, and muscularization of pulmonary artery. We also revealed that fluvastatin treatments prevented the hypoxia-induced decrease in cGMP production in the rat lung and restored the endothelium-dependent relaxation in the pulmonary artery. We revealed that this beneficial effect was not dependent on the increase in eNOS mRNA or protein expression, but was dependent on the inhibition of the eNOS-tight coupling with caveolin-1, the eNOS dissociation from heat shock protein 90, and the decrease in eNOS Ser 1177 –phosphorylation induced by hypoxia. Furthermore, in a whole-mount immunostaining the hypoxia-induced eNOS protein condensation with caveolin-1 of pulmonary endothelial cells was restored by the fluvastatin-treatment. Conclusion— These results suggest that the fluvastatin exerts beneficial effects on chronic hypoxia-induced pulmonary hypertension by protecting against the eNOS activity at the post-transcriptional level.

We studied the characteristics of the rhythmicity of heart rate (HR), body temperature (BT), locomotor activity (LA) and autonomic nervous activity in bronchial-hypersensitive (BHS) and bronchial-hyposensitive (BHR) guinea pigs. For this purpose, HR, BT, LA, and electrocardiogram (ECG) were recorded from conscious and unrestrained guinea pigs using a telemetry system. Autonomic nervous activity was analyzed by power spectral analysis of heart rate variability. Nocturnal patterns, in which the values in the dark phase (20:00-06:00) were higher than those in the light phase (06:00-20:00), were observed in HR, BT and LA in both strains of guinea pigs. The autonomic nervous activity in BHS guinea pigs showed a daily pattern, although BHR guinea pigs did not show such a rhythmicity. The high frequency (HF) power in BHS guinea pigs was higher than that in BHR guinea pigs throughout the day. Moreover, the low frequency/high frequency (LF/HF) ratio in BHS guinea pigs was lower than that in BHR guinea pigs throughout the day. These results suggest that parasympathetic nervous activity may be predominant in BHS guinea pigs.

To clarify the role of the autonomic nervous system in cardiovascular and emetic responses, we studied the influence of drugs that act on autonomic nervous function on emetic and cardiovascular responses induced by chemical or mechanical stimulation to the stomach in two strains of Suncus murinus, Jic:SUN-Her and Jic:SUN-Ler. Latency to the first retching in Jic:SUN-Her was significantly shorter than that in Jic:SUN-Ler to both mechanical and chemical stimulation. This result indicated that there are different sensitivities to mechanical and chemical stimulation to the stomach in these two strains of suncus. However, the numbers of emetic episodes were almost the same in these two strains. Mean blood pressure significantly increased from baseline prior to retching in both strains. Heart rate decreased in Jic:SUN-Her and increased in Jic:SUN-Ler prior to retching, suggesting that a different baroreflex responsiveness might exist in these two strains of suncus. Administration of acetylcholine and phenylephrine affected emetic response induced by mechanical and chemical stimulation. Although the baseline values of mean blood pressure and heart rate after administration of these drugs were different, changes in mean blood pressure and heart rate prior to retching were unaffected. This result suggested that the state of autonomic activity before the emetic response might be important in the development of the emetic response. Pretreatment with hexamethonium suppressed the cardiovascular response prior to retching and prolonged the latency to the first retching. This result indicated that there was an interaction between the mechanisms involved in cardiovascular and emetic responses. The change in autonomic function during the emetic response, especially enhancement of sympathetic activity prior to retching, may be relevant to emetic and cardiovascular responses. Moreover, these results suggest that different autonomic function or different baroreflex responsiveness in Jic:SUN-Her and Jic:SUN-Ler may be involved in emetic responses.

We studied characteristics of the daily pattern of heart rate (HR), blood pressure (BP), body temperature (BT), and locomotor activity (LA) in conscious and unrestrained Kurosawa and Kusanagi-Hypercholesterolemic (KHC) rabbits and age-matched normal Japanese white (JW) rabbits, using a telemetry system. In all JW rabbits, nocturnal patterns were observed in HR, BT and LA. In the 5 months group of KHC rabbits, however, diurnal rhythm was observed in HR, and in the 10 months group of KHC rabbits, it was also shown in LA. The nocturnal pattern was observed only in BT in 10 months KHC rabbits. Mean blood pressure (MBP) in JW and KHC rabbits showed no clear daily pattern. The mean daily values of HR and BT were not altered between the 5 months and 10 months groups in KHC rabbits, although those in JW were lower in the 10 months group than in the 5 months group. Moreover, the daily values of HR and MBP in KHC rabbits tended to be higher than those in the age-matched JW rabbits. The pulse pressure in the 10 months group of KHC rabbits tended to be greater than the 5 months groups of KHC and JW rabbits. Furthermore, short-term variabilities in BP in the 5 months KHC rabbits were significantly lower than those in the other groups. From these results, it is suggested that the cardiovascular function, including the autonomic nervous function is altered with the development of atherosclerosis in KHC rabbits.

We investigated whether transforming growth factor beta (TGF-beta) is involved in the growth of malignant mesothelioma (MM) cells in culture. TGF-beta production was examined in two mesothelioma cell lines (MeET-4 and -6) that were established from rat spontaneous MM in our laboratory. TGF-beta bioactivity in conditioned medium of these cell lines was analyzed using a CCL64 mink lung epithelial cell growth inhibition assay and found to be 30-70 times higher than that of normal rat mesothelial cells (MCs). The MM cell lines also showed considerably higher levels of TGF-beta mRNA expression when compared with MCs. The bioactivity and mRNA expression level were greater in MeET-4 than MeET-6. When MeET-4 was treated with antisense TGF-beta1 oligonucleotide (ODN), a significant decrease in both anchorage-dependent and -independent growth was observed. Treatment with exogenous TGF-beta resulted in no effects on the growth pattern of the MM cell lines, while proliferation of the MCs was slightly induced. It is considered that TGF-beta appears to be produced by rat spontaneous MM cells through an autocrine mechanism and could modulate the malignant growth of the tumor cells.

We studied the characteristics of the rhythmicity of heart rate (HR), body temperature (BT), and locomotor activity (LA) in conscious and unrestrained guinea pigs using a telemetry system. HR and/or LA in some guinea pigs clearly showed circadian rhythms, but in others there were no significant daily patterns; BT did not show significant daily rhythms. These results suggest that guinea pigs might have different individual characteristics of rhythmicity, and we should, therefore, be careful when using guinea pigs in chrono-biomedical research. We believe that the results of this study may be useful for future biomedical studies using guinea pigs.

To clarify the effect of acetylcholinesterase (AChE) on the pathogenesis of airway hyperresponsiveness, AChE activities in tracheal smooth muscle and lung tissue from congenitally bronchial-hypersensitive (BHS) and bronchial-hyposensitive (BHR) guinea pigs were compared. For this purpose, AChE activities were determined by measuring the rate of absorbance of tisssue homogenate. Relative amounts of AChE mRNA were also evaluated by the RT-PCR method. In both tracheal smooth muscle and lung tissue from BHS, the AChE activity and the relative amount of AChE mRNA were less than those in BHR. These results suggest that the reduced AChE activity is at least a candidate for inducing airway hyperresponsiveness.

We investigated the Ca(2+) signaling pathways of the response to angiotensin II in pleural mesothelial cells and the role of these Ca(2+) signaling pathways in mesothelial cell proliferation. Rat pleural mesothelial cells were maintained in vitro, and the Ca(2+) movement to angiotensin II was evaluated using the fluorescent Ca(2+) indicator fura 2. Furthermore, proliferation of mesothelial cells was assessed using a spectrophotometric 3-(4, 5-dimethylthazol-2-yl)-2,5-diphenyl-2H-tetrasodium bromide (MTT) assay. Angiotensin II (1 pM-100 microM) induced in mesothelial cells a biphasic elevation of intracellular Ca(2+) concentration ([Ca(2+)](i)) that consisted of a transient initial component, followed by a sustained component. Neither removal of extracellular Ca(2+) nor inhibition of Ca(2+) influx by 1 microM nifedipine affected the angiotensin II-induced initial transient elevation of [Ca(2+)](i) in mesothelial cells. Nifedipine did not block angiotensin II-induced sustained elevation of [Ca(2+)](i). Angiotensin II (1 pM-100 microM) had a proliferative effect on mesothelial cells in a dose-dependent manner. Angiotensin II type 1 (AT(1)) receptor antagonist ([Sar(1), Ile(8)]angiotensin II) inhibited both angiotensin II-induced elevation of [Ca(2+)](i) and proliferation of mesothelial cells. Pertussis toxin did not affect angiotensin II-induced responses. These results suggest that angiotensin II-induced responses to mesothelial cells are extremely dependent on the angiotensin AT(1) receptor coupled with pertussis toxin-insensitive G protein.

From proteolytic digest of swine hemoglobin, we isolated four peptide, E-1 (Phe-Gln-Lys-Val-Val-Ala), E-2 (Phe-Gln-Lys-Val-Val-Ala-Gly), peptide 30-3 (Phe-Gln-Lys-Val-Val-Ala-Lys) and H-1 (Gly-Lys-Lys-Val-Leu-Gln). These peptides inhibited angiotensin I-converting enzyme activity with an IC50 of 5.8, 7.4, 2.1 and 1.9 microM, respectively. Oral administration of 50 mg/kg E-1 and 50 mg/kg H-1 decreased blood pressure in spontaneously hypertensive rats. In normotensive rats, oral administration of 500 mg/kg E-1 and 500 mg/kg H-1 inhibited the pressor effect of i.v. administrated 300 ng/kg angiotensin I, possibly by inhibiting its conversion to angiotensin II. These results suggest that these peptides are orally effective inhibitors of angiotensin I-converting enzyme that have a hypotensive effect.

This study shows the effects of a selective endothelin ET(B) receptor agonist, IRL 1720 {Ac-[Ala11,15]endothelin-1-(8-21)}, on cardiovascular responses in anesthetized spontaneously hypertensive rats and Wistar-Kyoto rats. Single intravenous bolus injection of IRL 1720 caused a dose-related short-lasting fall in blood pressure, left ventricular pressure and myocardial contractility. However, repeated intravenous bolus injection of 10(-5) mol/kg IRL 1720 produced a biphasic response consisting of an initial short-lasting decrease followed by a sustained increase in these parameters. The initial decrease was reduced, whereas the following increase was enhanced with the repeated injections of IRL 1720. The cardiovascular pressor response was not inhibited by the endothelin ET(A) receptor antagonist, FR139317 ((R)2-[(R)-2-[(S)-2-[[1-(hexahydro-1H-azepinyl)]carbonyl] amino-4-+methylpentanoyl] amino-3-[3-(1-methyl-1H-indolyl)]propionyl]amino -3- (2-pyridyl)propionic acid). The effects of IRL 1720 were qualitatively similar but more potent in spontaneously hypertensive rats than in Wistar-Kyoto rats. These results suggest the existence of two types of endothelin ET(B) receptor for IRL 1720: a tachyphylactic endothelin ET(B) receptor that mediates cardiovascular depressor responses and a less tachyphylactic endothelin ET(B) receptor that mediates pressor responses in the rat.

Taurine is a semi-essential amino acid widely distributed in the body and we take in it from a wide range of nutritive-tonic drinks to improve health. To date, we have elucidated that oral supplementation of taurine does not affect learning and memory in the rat. However, there are few studies concerning the direct effects of taurine in the brain at the behavior level. In this study, we intracerebroventricularly administered taurine to rats and aimed to elucidate the acute effects on learning and memory using the Morris water maze method.Escape latency, swim distance, and distance to zone, which is the integral of the distance between the rats and the platform for every 0.16 seconds, were adopted as parameters of the ability of learning and memory. We also tried to evaluate the effect of intraperitoneal taurine administration.Escape latency, swim distance, and distance to zone were significantly longer in the intracerebroventricularly taurine-administered rats than in the saline-administered rats. Mean swimming velocity was comparable between these two groups, although the physical performance was improved by taurine administration. Probe trials showed that the manner of the rats in finding the platform was comparable. In contrast, no significant differences were found between the intraperitoneally taurine-administered rats and the saline-administered rats.These results indicate that taurine administered directly into the brain ventricle suppresses and delays the ability of learning and memory in rats. In contrast, it is implied that taurine administered peripherally was not involved in learning and memory.

Diurnal fluctuations of heart rate and locomotive activity were observed in the unanesthetized and unrestrained voles (Microtus arvalis) and mice, and the differences in these biological characters between voles and mice were also investigated. The mean heart rate of vole in whole day was lower than that of mice. In voles, there were no significant differences in the mean heart rate between in light period and in dark period. It was observed that most of voles were active in not only dark period but light period. On the other hand, in mice, the mean heart rate in dark period was significantly higher than that in light period, and the nocturnal habit was shown obviously in the locomotive activity. In voles, the ultradian rhythmicities of 95-210 min in the heart rate and those of 160-210 min in the locomotive activity were recognized, and the fluctuations of heart rate due to ultradian rhythmicity in voles exceeded the difference between the heart rate in light period and that in dark period. In mice, one of three animals showed the ultradian rhythmicity of 85 min in the fluctuation of heart rate. Diurnal fluctuation of the heart rate in voles consisted of the two patterns which the peaks of heart rate were coincident with the active period or the resting period. However, all the peaks of heart rate in mice were coincident with the active period. These results suggested that the fluctuations of heart rate in voles were dependent on ultradian rhythmicities in addition to the circadian rhythmicities.

This study was designed to assess the effect of hyperlipidemia on cardiovascular responses to adrenergic stimulation in a porcine model. Four-week-old piglets (n = 10) were divided into two groups; one fed a control diet and the other was fed an atherogenic diet for 8 weeks. Cardiovascular responses were evaluated to both norepinephrine (NE; 0.5 and 2.5 micrograms/kg) and isoproterenol (ISO; 0.1 and 0.5 microgram/kg) from simultaneous recordings of femoral arterial pressure, heart rate, left intraventricular pressure and left intraventricular dP/dt. It was found that no significant difference in the baseline values of cardiovascular function was observed between the control and hyperlipidemic groups. However, in the hyperlipidemic group as compared with the control group: 1) arterial blood pressure responses to NE were significantly increased (P less than 0.05), 2) cardiac contractile responses to NE and ISO were significantly potentiated (P less than 0.05), and 3) reflex bradycardia in response to increasing arterial blood pressure did not occur. These findings indicate that hyperlipidemia can potentiate the cardiovascular responses to adrenergic stimulation, whereas reflex cardiovascular regulation is somewhat altered by hyperlipidemia. Conceivably, these observations may have relevance to the possible role of the mechanism of the interaction of hyperlipidemia and hypertension in atherogenesis.

Exposure to cold temperature might affect on cardiovascular and autonomic nervous function. Although there are a lot of studies on physiological and pathophysiological responses of taurine, it was poorly understood the effects of taurine on cardiovascular and autonomic nervous function during cold circumstances. Therefore, the purpose of this study was to clarify the possible role of taurine on cardiovascular and autonomic nervous function in rats exposed to cold temperature. For this purpose, heart rate, blood pressure and locomotive activity were recorded from conscious and unrestrained rats using a telemetry system. Moreover, the autonomic nervous function was investigated by power spectral analysis of heart rate variability. After the recovery period of implantation of transmitter, 1% taurine was supplied during experimental period ad libitum. After the 7 days control period, both taurine administrated and control groups of rats were exposed a cold temperature. There were no differences in heart rate, blood pressure and locomotive activity between taurine and control groups before cold exposure. However, parasympathetic nervous function was somewhat predominant in taurine group. Heart rate and blood pressure in both groups increased greatly by cold exposure. Heart rate in taurine group was much higher than that in control group. LF and HF powers were decreased by cold exposure in both groups. Although no differences were observed in LF, decrease of HF in taurine group was greater than that in control group. These results suggested that taurine might provide some reservoir for cardiovascular and autonomic nervous function to cold stress in rats.

Many epidemiological studies have shown that polyphenols can reduce the risk of mortality from cardiovascular diseases. This study tested the hypothesis that cacao liquor polyphenols have the properties to restore the cardiovascular and autonomic nervous function in an animal model of familial hypercholesterolaemia. Male Kurosawa and Kusanagi-hypercholesterolaemic rabbits were housed in individual cages in a room where a 12-hr light:dark cycle (lights-on at 8:00 and lights-off at 20:00) was maintained. At 3 months of age, they were divided into two groups (standard diet and cacao liquor polyphenol) and the animals received 100 g of the respective diets per day and were provided with tap water ad libitum. Heart rate and blood pressure were measured by a telemetry system. To clarify the autonomic nervous function, power spectral analysis of heart rate variability, baroreflex sensitivity and autonomic nervous tone were measured. After 6 months of dietary administration of cacao liquor polyphenols, heart rate and blood pressure were lowered but plasma lipid concentrations were unchanged. The area of atherosclerotic lesions in the aorta in the cacao liquor polyphenol group was significantly smaller than that in the standard diet group. The high-frequency power of heart rate variability in the rabbits in the standard diet group was significantly decreased with ageing, but that in the cacao liquor polyphenol group was not different between short-term and long-term treatment. Moreover, cacao liquor polyphenols preserved parasympathetic nervous tone, although that in the standard diet group was significantly decreased with ageing. We conclude that cacao liquor polyphenols may play an important role to protect cardiovascular and autonomic nervous functions.

International audience; The characteristics of autonomic nervous activity were examined on captive great cormorants Phalacrocorax carbo hanedae, using a power spectral analysis of heart rate variability. Heart rates were calculated from recordings of the electrocardiograms of the birds via embarked data loggers. We investigated the effects of blockades of the sympathetic or parasympathetic nervous systems using the indices of autonomic nervous activity such as high frequency (0.061-1.5 Hz) component, low frequency (0.02-0.060 Hz) component and the low frequency power component to high frequency power component ratio. Resting heart rate (85.5 ± 6.1 bpm) was lower than the intrinsic heart rate (259.2 ± 15.3 bpm). The heart rate drastically increased after the injection of the parasympathetic nervous blocker, on the other hand it slightly decreased after the injection of the sympathetic nervous blocker. The sympathetic, parasympathetic and net autonomic nervous tones calculated from heart rate with and without blockades were 40.9 ± 27.6, -44.5 ± 7.4 and -29.5 ± 9.0%, respectively. The effect of the parasympathetic nervous blockade on low frequency and high frequency power was greater than that of the sympathetic nervous blockade. Those data suggested that the parasympathetic nervous activity was dominant for great cormorants.

Proinflammatory cytokines, including IL-1, exert pleiotropic effects on the neuro-immuno-endocrine system. Previously, we showed that mice with knockout of the gene encoding IL-1 receptor antagonist (Il1ra (-/-), also known as Il1rn (-/-)) have a lean phenotype. The present study was designed to analyse the mechanisms leading to this lean phenotype.Il1ra (-/-) mice were fed a high-fat diet following weaning. Energy expenditure, body temperature, heart rate, blood parameters, urinary catecholamines and adipose tissue were analysed.Il1ra (-/-) mice exhibited resistance to obesity induced by a high-fat diet; this resistance was associated with increased energy expenditure and a decreased respiratory quotient, indicating that the ratio of fat:carbohydrate metabolism in Il1ra (-/-) mice is greater than in controls. Activity level in Il1ra (-/-) mice was significantly decreased and body temperature was significantly increased, compared with wild-type (WT) mice. Inguinal white adipose tissues in Il1ra (-/-) mice express increased levels of Ucp1 and mitochondrial respiratory chain genes compared with WT mice. Histological analysis of adipose tissue in Il1ra (-/-) mice revealed that brown adipose tissue is hyperactive and inguinal white adipose tissue contains smaller cells, which exhibit the distinctive multilocular appearance of brown adipocytes. Urinary epinephrine and norepinephrine excretion in Il1ra (-/-) mice was significantly increased compared with WT mice, suggesting that Il1ra (-/-) mice have increased sympathetic tone. Consistent with this, heart rate in Il1ra (-/-) mice was also significantly increased.Our results show that Il1ra (-/-) mice have increased energy expenditure, fat:carbohydrate oxidation ratio, body temperature, heart rate and catecholamine production. All of these observations are consistent with an enhanced sympathetic tone.

The airway responsiveness to bradykinin (0.1, 1 and 10 microg/kg, i.v.) was examined in two lines of guinea pigs, BHS (bronchial hypersensitive) and BHR (bronchial hyposensitive) lines, with different airway sensitivity to inhalation of acetylcholine (ACh)-aerosol. Normal Hartley strain guinea pigs were used as a control group. The airway contraction was measured by recording intratracheal pressure (P[IT]) and respiratory airflow (V) under the condition of artificial ventilation in anesthetized guinea pigs. The results show airway responsiveness to bradykinin in BHS guinea pigs to be significantly greater than in BHR and normal Hartley strain guinea pigs.

The time courses of changes in cardiovascular and autonomic nervous functions during acclimatization to hypoxia were studied in conscious Sprague-Dawley rats. The animals were kept under a 12:12-h light-dark cycle and exposed to hypoxia (1 atm, 10% O2). Implanted telemetry transmitters were used to record blood pressure (BP). Changes in heart rate (HR) and BP were monitored over a 21-day period, and variations before and during hypoxia were analyzed using the wavelet transform method. The HR, high-frequency power of HR variability (HR-HF) and low-frequency power of BP variability (BP-LF) were all significantly increased after 1 h of hypoxia, whereas the LF/HF ratio of HR variability did not change. After this initial increase, both HR and the BP-LF were found to decrease. On the first day of hypoxia, HR and BP-LF values were significantly lower than those of the control rats, whereas the HR-HF was higher. Subsequently, these values altered so that they were similar to the control after 14 days of hypoxia. In addition, the amplitude of diurnal variation in HR was reduced during hypoxia. These results suggest that a sequence of dynamic interactions between sympathetic and parasympathetic nervous activities might have important roles in the regulation of cardiovascular function during acclimatization to hypoxia.

This study investigated the effects of pair housing on diurnal rhythms of heart rate and autonomic nervous activity in miniature swine. For this purpose, six adult Gottingen miniature swine were initially housed individually in an animal cage. Then, two of each swine were housed in a large cage together for 3 weeks. After that swine were separated into individual cages again. During this experimental procedure, electrocardiogram (ECG) was recorded with a Holter ECG recorder. Autonomic nervous activity was evaluated by power spectral analysis of heart rate variability. Heart rate and autonomic nervous activity clearly showed a diurnal rhythm in miniature swine housed in individual cages. When two swine were housed together, heart rate was significantly increased throughout the day and diurnal rhythm disappeared. Although these changes gradually recovered to basal levels, these parameters had not completely returned to basal levels even after 2 weeks. Heart rate was still higher than the initial level just after swine were re-housed in their own individual cages. Heart rate and autonomic nervous activity returned to basal levels about 2 weeks after re-housing. Further, heart rate in some swine decreased below their initial levels. These results suggest that it takes miniature swine at least 2 weeks to adapt to different circumstances. Furthermore, the power spectral analysis of heart rate variability can be used as a useful method in a study for answering controversial issues related to stress response.

We investigated the characteristics of autonomic nervous function in Zucker-fatty and Zucker-lean rats. For this purpose, a long-term electrocardiogram (ECG) was recorded from conscious and unrestrained rats using a telemetry system, and the autonomic nervous function was investigated by power spectral analysis of heart rate variability (HRV). Although heart rate (HR) in Zucker-fatty rats was lower than that in Zucker-lean rats throughout 24 h, apparent diurnal variation in HR was observed in both strains and HR during the dark period was significantly higher than that in light period. Diurnal variation in locomotor activity (LA) in Zucker-fatty rats was also observed, but LA was lower than that in Zucker lean rats, especially during the dark period. There were no significant differences, however, in high-frequency (HF) power, low-frequency (LF) power, and the LF/HF ratio between Zucker-fatty and Zucker-lean rats. The circadian rhythm of these parameters was mostly preserved in both strains of rats. Moreover, the effect of autonomic blockades on HRV was nearly the same in Zucker-fatty and Zucker-lean rats. These results suggest that the autonomic nervous function of insulin-resistant Zucker-fatty rats remain normal, from the aspect of power spectral analysis of HRV.

The present study assessed the effects of bovine milk-derived lactoferrin (bLf) on distress activities induced by maternal separation in 5- to 18-day-old rat pups. The rat pups were injected with BSA (100 mg/kg, i.p.; control) or bLf (100 mg/kg, i.p.) 30 min before the behavioral test. Distress activity was estimated by means of recording body movements or ultrasonic vocalizations (USVs). After 5 min of maternal separation, bLf significantly (P

Mechanisms underlying the Ca2+-activated K+ channel (K(Ca)) blockers-induced oscillatory contractions were investigated in guinea pig tracheal smooth muscle. The mean oscillatory frequencies induced by charybdotoxin (ChTX; 100 nM) and iberiotoxin (IbTX; 100 nM) were 9.8+/-0.8 (counts/h) and 8.0+/-1.3 (counts/h), respectively. Apamin (1 microM ), a blocker of SK(Ca), induced no contraction in guinea pig trachea and did not affect ChTX-induced oscillatory contractions. In Ca2+ free solution, no ChTX-induced contraction was observed. Nifedipine (100 nM), a blocker of voltage-dependent Ca2+ channels, and SK&F 96365 (10 microM), a blocker of capacitative Ca2+ entry, completely abolished ChTX-induced oscillatory contractions. Ryanodine (1 microM) decreased the amplitude, but increased the frequency of the oscillatory contractions. Thapsigargin (1 microM) changed contractions from the oscillatory type to the sustained type. Moreover, the protein kinase C (PKC) inhibitor, bisindolylamaleimide I (1 microM), decreased the amplitude and frequency, but PKC activator, phorbol 12-myristate 13-acetate (1 microM), increased the frequency of oscillatory contractions. These results suggest that K(Ca) inhibitors-induced oscillatory contractions are initiated by Ca2+ influx through L-type voltage-dependent Ca2+ channels. The ryanodine-sensitive calcium release channels in the sarcoplasmic reticulum may play an important role in maintaining the oscillatory contractions. Moreover, PKC activity modulates these oscillatory contractions.

We established characteristics of power spectral analysis of heart rate variability, and assessed the diurnal variations of autonomic nervous function in guinea pigs. For this purpose, an electrocardiogram (ECG) was recorded for 24 hr from conscious and unrestrained guinea pigs using a telemetry system. There were two major spectral components, at low frequency (LF) and high frequency (HF) bands, in the power spectrum of HR variability. On the basis of these data, we defined two frequency bands of interest: LF (0.07-0.7 Hz) and HF (0.7-3.0 Hz). The power of LF was higher than that of HF in the normal guinea pigs. Atropine significantly reduced power at HF. Propranolol also significantly reduced power at LF. Furthermore, the decrease in the parasympathetic mechanism produced by atropine was reflected in a slight increase in the LF/HF ratio. The LF/HF ratio appeared to follow the reductions of sympathetic activity produced by propranolol. Autonomic blockade studies indicated that the HF component reflected parasympathetic activity and the LF/HF ratio seemed to be a convenient index of autonomic balance. Nocturnal patterns, in which the values of heart rate in the dark phase (20:00-06:00) were higher than those in the light phase (06:00-20:00), were observed. However, the HF, LF and the LF/HF ratio showed no daily pattern. These results suggest that the autonomic nervous function in guinea pigs has no clear circadian rhythmicity. Therefore, this information may be useful for future studies concerning the autonomic nervous function in this species.

Diurnal fluctuations of heart rate (HR), body temperature (BT) and locomotor activity (LA) in the unanaesthetized and unrestrained house musk shrew (Suncus murinus) were studied using a telemetry system. Six adult male shrews (Jic:SUN) weighing 60-70 g were used in the present study. They were housed under conditions of 24 C and a 12/12-hr light-dark cycle. HR, BT and LA were recorded over 10 days, following the post-implantation period (10 days or more) of the telemetric transmitter. A clear nocturnal rhythm of LA was shown, while intermittent and short-term LA were shown during the light period. The mean HR was 323.5 +/- 8.8 bpm in the light period and 354.3 +/- 5.2 bpm in the dark period, and the fluctuation of HR showed a nocturnal pattern. A nocturnal pattern was also observed in BT fluctuation, and all animals lowered their body temperature from 35-37 C to approximately 30 C or below, mostly during the light period. The fall of body temperature progressed over 2-3 hr, and then rose to the baseline temperature rapidly within approximately 30 min. While the body temperature fell, HR markedly decreased to approximately 100 bpm. These results suggest that the shrew has unique physiological properties in maintaining metabolic balance which are anticipated to be caused by the dramatic alteration of the autonomic nervous function.

An autolysate of bonito bowels was treated with ultrafiltration, loose RO concentration, ion-exchange chromatography, and reverse phase chromatography to increase its potency to inhibit angiotensin I-converting enzyme (ACE) activity by 16-fold. Oral administration of the partially purified autolysate decreased the systolic blood pressure of spontaneously hypertensive rats (SHR) in a dose-dependent manner at the doses of 1 g peptides/kg or higher. The relationship between the antihypertensive activity (in vivo) of the partially purified preparation and its ACE inhibitory activity (in vitro) in comparison with previously reported ACE inhibitory peptides is discussed.

The expression balance of M2 and M3 muscarinic receptor subtypes on the pathogenesis of airway hyperresponsiveness was investigated by using two congenitally related strains of guinea pigs, bronchial-hypersensitive (BHS) and bronchial-hyposensitive (BHR). CCh-induced airway responses in vivo and in vitro were investigated by comparing the effects of muscarinic receptor subtype antagonists, and the relative amounts of M2 and M3 muscarinic receptor mRNA in tracheal smooth muscle and lung tissue were investigated. After treatment with muscarinic receptor subtype antagonists, the ventilatory mechanics (VT, Raw, and Cdyn) of response to CCh aerosol inhalation were measured by the bodyplethysmograph method. The effects of these antagonists on CCh-induced tracheal smooth muscle contraction were also investigated. The effects of M2 muscarinic receptor blockade were less but the effects of M3 muscarinic receptors blockade on the airway contractile responses were greater in BHS than in BHR. In M3 muscarinic receptor blockades, CCh-induced tracheal contractions in BHS were significantly greater than those in BHR. In tracheal smooth muscle from BHS, the relative amount of M2 muscarinic receptors mRNA was less but that of M3 muscarinic receptor mRNA was more than those in BHR. These results suggest that the high ACh level as a consequence of dysfunction of M2 muscarinic autoreceptors and the excessive effect of M3 muscarinic receptors on the airway smooth muscle may play an important role in the pathogenesis of airway hyperresponsiveness.

Tail blood flow (TBF) in the rat markedly increases during sympathetic withdrawal such as hyperthermia or lumbar sympathetic blockade. However, a long-term alteration of TBF after chronic sympathetic denervation is not well understood. In the present study, TBF following lumbar sympathectomy (LSX) was observed to ascertain whether subsequent changes in TBF occur in the absence of the sympathetic nervous activity in the rat tail. Assessed by recording tail and rectal temperature, the LSX immediately caused an increase in TBF. TBF was gradually decreased along with time and returned to the sham operated (SO) control level within 4 days. About a week after the surgery, a rapid increase in TBF in response to whole body heating was almost abolished in denervated animals. Neither hexamethonium (20 mg/kg, i.v.) for ganglion blockade nor intra-arterial infusion of alpha-receptor antagonist, phentolamine (10, 100 microg) produced vasodilation in LSX animals. Nitroprusside, a donor of nitric oxide, produced an increase in TBF in both LSX and SO animals. These results indicate that the tail vasculature after LSX constricts with capability to be vasodilated independent of sympathetic reinnervation. Quantification of the tail vascular mRNA expression by reverse transcriptase-polymerase chain reaction showed less endothelial nitric oxide synthetase in LSX group than that in SO group whereas endothelin-1 was not significantly different in both groups. It is suggested that functional changes in tail vascular endothelium takes at least a part in the reduction in TBF after LSX.

The characteristics of airway responsiveness to acetylcholine (ACh) in congenitally bronchial-hypersensitive (BHS) and bronchial-hyposensitive (BHR) guinea pigs were clarified in vivo and in vitro. We measured the change in ventilatory mechanics in response to ACh inhalation by means of the bodyplethysmograph and the contractile responses of isolated trachea to ACh and carbachol (CCh). Further, muscarinic receptor subtypes involved these responses were identified. The basal values for ventilatory mechanics in BHS were not significantly different from those in BHR. Respiratory resistance to ACh was progressively increased in a time- and dose-dependent manner in BHS. The contractile responses of tracheal smooth muscle to ACh in BHS were significantly greater than those in BHR, but CCh-induced responses in BHS and BHR were similar. ACh- and CCh-induced contractions were mediated via M3 receptors. These results suggested that the falling-down of BHS in response to ACh inhalation was caused by the strong constriction of the airway and the reduction in ventilation. Moreover, the airway hyperresponsiveness to ACh in BHS might be partly dependent on the change in acetylcholinesterase activity.

We investigated the endothelin production and endothelin receptor activity of pericardial mesothelial cells obtained from spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. The pericardial mesothelial cells were maintained in vitro and the production of endothelin-1 by these cells was evaluated by using a sensitive sandwich-type enzyme immunoassay for endothelin-1 and big endothelin-1. Endothelin receptor subtypes were pharmacologically analyzed by measuring the changes of intracellular Ca2+ concentration ([Ca2+]i) in pericardial mesothelial cells. Mesothelial cells from both strains produced more immunoreactive endothelin-1 than big endothelin-1. The production of immunoreactive endothelin-1 progressively increased in a culture time-dependent manner. The amount of immunoreactive endothelin-1 detected after 72 h in pericardial mesothelial cells of SHR was significantly (P0.05) higher than that in the cells of WKY rats (SHR: 196.7 +/- 19.1 pg/10(6) cells; WKY: 122.7 +/- 10.6 pg/10(6) cells). Endothelin-1 and endothelin-3 induced elevation of [Ca2+]i in pericardial mesothelial cells. The selective agonist of the endothelin ETB receptor, sarafotoxin S6c, also induced elevation of [Ca2+]i. The endothelin- and sarafotoxin S6c-induced elevations of [Ca2+]i in pericardial mesothelial cells from SHR were greater than those in mesothelial cells from WKY rats. The endothelin ETB receptor antagonist, IRL 1038 ([Cys11,Cys15]endothelin-1-(11-21)), significantly inhibited the endothelin-1- and endothelin-3-induced changes in [Ca2+]i. The endothelin ETA receptor antagonist, FR 1393171 ((R)2-[(R)-2-[(S)-2-[[1-(hexahydro-1H-azepinyl)]carbonyl]ammino -4-methylpentanoyl]amino-3-[3-(1-methyl-1H-indoyl)]propio nyl]amino-3-(2-pyridyl)propionic acid), did not affect these changes. From these results, pericardial mesothelial cells from both SHR and WKY rats shared the ability to produce endothelin-1 spontaneously in culture, although consistently greater production was detected in cultures of SHR origin. Moreover, pericardial mesothelial cells of SHR origin may have increased numbers of endothelin ETB receptors and/or a more active signal transduction system compared with those of WKY rats. These results suggest that endothelin-1 may play an important role in the pericardium in an autocrine and/or paracrine fashion.

Electrolyte abnormalities have become an increasingly important cause of arrhythmias owing to the widespread use of high-potency diuretics. Hypokalemia is one of the common complications of diuretic use. Although some studies of hypokalemia induced by furosemide as well as of potassium-deficient diets in the rat have been reported, the electrocardiographic (ECG) changes during hypokalemia in the rat are poorly understood. This study was designed to examine such changes. For this purpose, hypokalemia was induced by furosemide administration, and the diagnostic criteria for ECG manifestations of hypokalemia were determined. During hypokalemia, conduction in most parts of the heart was suppressed to an extent depending on plasma potassium concentration. Prolongation of the QT interval was also observed, which agrees with findings in humans and dogs. Furthermore, prolonged durations of the P wave and QRS complex were observed during hypokalemia in the rat. The extent of alteration of the PR interval induced by hypokalemia was less significant than that of P wave and QRS complex durations. These results suggest that the excitabilities of the myocardium in the atria and ventricles may be affected by extracellular potassium level rather than by the atrioventricular conduction system in the rat. Wave amplitude, except that of the P wave, was decreased by severe hypokalemia. These changes were not dependent on the plasma potassium concentration. Typical T wave changes observed with hypokalemia in humans and dogs did not occur in the rat. The ECG manifestations of acute hypokalemia in the rat did not include the typical T wave changes seen in species with ST-segment type ECGs; however, other ECG parameter changes occurring with hypokalemia were qualitatively similar to those in other species. These results may be useful for testing the toxicity of potassium-depleting drugs in the rat.

Airway hyper-responsiveness is known as an important pathogenesis of asthma. In the present study, the airway responsiveness to aerosolized and injected histamine in congenitally bronchial-hypersensitive (BHS) and bronchial-hyposensitive (BHR) guinea pigs was investigated. In addition, the role of the vagal reflex in histamine-induced airway contraction was evaluated by vagal blocking with atropine inhalation or bilateral vagotomy. A significantly higher bronchoconstrictive reaction, i.e., a decrease in tidal volume (VT) and an increase in respiratory resistance (Rrs), to histamine-inhalation was observed in BHS than in BHR. A noticeably lower reduction in VT was noted after atropine pretreatment for both BHS and BHR, whereas an increase in Rrs was inhibited only in BHS. The intravenous injection of histamine caused a noticeable bronchoconstrictive reaction in both BHS and BHR with a dose-dependent relationship, but no significant differences were observed and the bilateral vagotomy failed to induce any difference between the two animal groups. These results demonstrated that the airway responsiveness to histamine is considerably different in BHS from that in BHR, but the difference is largely dependent on the route of administration of histamine. The important role of the vagal reflex on the elicitation of airway contraction was elucidated in both animal groups, and it appeared that the BHS possessed relatively higher dependency on the vagal reflex mechanism than the BHR.

We have studied the autonomic nervous function in voles ( Microtus arvalis) and mice. For this purpose, ECGs were recorded from conscious and unrestrained voles and mice using radiotelemetry and the autonomic nervous function was investigated by the power spectral analysis of heart rate variability. Heart rate in voles was lower than mice and the coefficient of variance was larger in voles. In the power spectra of voles and mice, there were two major spectral components with the high frequency (HF) peak generally appearing between 2.0 and 4.0 Hz, and the low frequency (LF) peak appearing below 0.6 Hz. On the basis of this data, we set the two frequency bands as LF (0.1-1.0 Hz) and HF (1.0-5.0 Hz) to evaluate autonomic nervous function. The LF and HF powers were larger in voles than mice. The LF/HF ratio was thought to provide a convenient index of autonomic nervous balance and was smaller in voles than mice. The LF powers in both species were reduced by atropine, but propranolol reduced the LF power only in mice. The HF power was reduced by atropine only in voles. The intrinsic heart rate produced by a double blockade with atropine and propranolol in voles was almost the same as control levels, but in mice was lower than controls. The ratio of the LF and HF powers by a double blockade were almost the same as those of the administration of atropine in voles, but nearer to propranolol in mice. These results suggested that the parasympathetic nervous function was predominant in voles, but the sympathetic one was predominant in mice.