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ABSTRACT In our previous studies, quantified saponins-rich fraction from adventitious root extract of Ficus religiosa L., Moraceae, showed anticonvulsant effect in acute, as well as chronic mice models of epilepsy. The present study was designed to reveal putative anticonvulsant mechanism of quantified saponins-rich fraction using target specific animal models. The anticonvulsant effect of quantified saponins-rich fraction was initially studied in maximal electroshock and pentylenetetrazol test at 1, 2 and 4 mg/kg; i.p. doses. Based on the results of initial anticonvulsant testing, different groups of mice were injected with vehicle or quantified saponins-rich fraction (4 mg/kg; i.p.), 30 min prior to an injection of N-methyl-D-aspartic acid (100 mg/kg; s.c.), bicuculline (5 mg/kg; i.p.), strychnine hydrochloride (2 mg/kg; i.p.), BAY k-8644 (37.5 µg; i.c.v.), veratridine (500 µg/kg; i.p.) and the convulsive episodes were studied. Treatment with the extract (1, 2 and 4 mg/kg) showed significant protection in maximal electroshock and pentylenetetrazol-induced convulsion tests, in a dose-dependent manner. Moreover, quantified saponins-rich fraction at 4 mg/kg dose showed significant increase in latency to clonic convulsions, decrease in seizure severity and increase in average wave amplitude in bicuculline, BAY k-8644 and veratridine tests, respectively, as compared to vehicle control. However, SRF treatment failed to abolish N-methyl-D-aspartic acid and strychnine-induced convulsions, indicated by insignificant change in the appearance of turning behavior and onset of tonic extension, respectively, as compared to vehicle control. From the results of present study, it is concluded that quantified saponins-rich fraction suppress maximal electroshock, pentylenetetrazol, bicuculline, BAY k-8644 and veratridine-induced convulsions, indicating its GABAergic, Na+ and Ca2+ channel modulatory effects. Further it can be correlated that quantified saponins-rich fraction causes deactivation of voltage-gated Na+ and Ca2+ channels, without effecting ligand-gated Na+ and Ca2+ channels. More studies are required at molecular levels using in vitro techniques to understand the exact molecular interactions of quantified saponins-rich fraction with these pathways.
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Objective To investigate the changes in intracellular Ca2+ in the ureter smooth muscle cells (USMC) of rats with neuropathic urinary tract dysfunction (NUTD) and their significance.Methods Forty-five rats were randomly and averagely divided into NUTD group,experimental control (EC) group and blank control (BC) group.The NUTD group was operated with a spinal cord transection at the first lumbar level and the sacral cord was destroyed;in EC group the spinal process was partly bitten at the same position,but the spinal cord was not transected;BC group was given no operations.One week later,the video-urodynamic was performed to observe the acontractile detrusor (ACD),vesicoureteral reflux (VUR) and urinary tract dysfunction in rats among the NUTD group,EC group and the BC group.Video-urodynamic assessment was performed at the sixth week after operation.Ureter smooth muscle cells (USMC) were obtained by collagenase digestion.Intracellular Ca2 + in the USMC were observed by laser scanning confocal microscope.Then the effects of Bay K8644(10-8 mol/L,10-7 mol/L,10-6 mol/L) on cytosolic Ca2+ concentrations([Ca2+] i) in NUTD group were studied by calculating the fluorescence intensity.Results ACD and no detrusor overactivity were found in all rats in NUTD group and without vesicoureteral reflux.Immunofluorescence method confirmed that the cells were USMC.Compared with BC group (31.44 ± 2.82) and EC group (32.06 ± 3.67),the fluorescence intensity (FI) of intracellular Ca2 + in USMC was much lower in the NUTD group (9.80 ± 1.11),and there was significant difference(P ＜ 0.05).Bay K8644 (10-8 mol/L,10-7 mol/L,10-6 mol/L) increased the FI of [Ca2 +] i in a concentration-dependent manner,which were 3.80 ± 1.30,10.04 ± 2.15,19.89 ± 2.06,respectively,and there was significant difference (P ＜ 0.05).Conclusions The decrease in Ca2 + concentration in the ureter smooth muscle cells may be one of the important factors for the primary ureteral dysfunction of NUTD.And calcium channel agonist can be meaningful for adjusting abnormal Ca2+ concentration in USMC of NUTD.
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Extracellular single-unit discharge recording technique was used to examine the effects of Ginkgolide B (BN52021) on the discharges of neurons in CAI area of hippocampal slices and to elucidate the mechanisms involved.The results showed that:(1) In response to the application of ginkgolide B (0.1,1,10 βμmol/L; n =43) into the perfusate for 2 rain,the spontaneous discharge rates (SDR) of 42/43 (97.67%) neurons were significantly decreased in a dose-dependent manner; (2) Pretreatment with L-glutamate (L-Glu,0.2mmol/L) led to a marked increase in the SDR of all 10 (100%) neurons in an epileptiform pattern.The increased discharges were suppressed significantly after ginkgolide B (1 μmol/L) was applied into the perfusate for 2 rain; (3) In 8 neurons,perfusion of the selective L-type calcium channel agonist,Bay K 8644 (0.1 μmol/L),induced a significant increase in the discharge rate of 8/8 (100%) neurons.Ginkgolide B (1 μmoL/L) applied into the perfusate inhibited the discharges of 7/8 (87.5%) slices; (4) In 8 neurons,the broad potassium channels blocker,tetraethylammonium (TEA,1 mmol/L) completely blocked the inhibitory effect of ginkgolide B (1 μmol/L).These results suggest that ginkgolide B can inhibit the electrical activity of CAI neurons.The inhibitory effect may be related to the blockade of L-type voltage-activated calcium channel and may be concerned with delayed rectifier potassium channel (KDR),which indicated that ginkgolide B play a protective role on the central neurons.
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AIM To elucidate the effect of rhynchophylline(Rhy) on carotid sinus baroreceptor activity (CBA). METHODS By recording sinus nerve afferent discharge activity with isolated carotid sinus perfusion, parameters of CBA, such as peak slope (PS), peak integral value (PIV), threshold pressure (TP) and saturation pressure (SP) were examined. ①Rhy 10, 50, and 100 μmol·L-1, dissolved in K-H solution, was perfused into isolated carotid sinus, then the effects of Rhy on parameters of CBA were observed while intrasinus pressure was altered in a stepwise manner. ②NG-nitro-L-arginine methyl ester (L-NAME) 10 mmol·L-1, tetraethylammonium (TEA) 1 mmol·L-1 and Bay K8644 500 nmol·L-1 were perfused into isolated carotid sinus, and effects of them on the response of carotid baroreceptor to Rhy were observed. RESULTS ① By perfusing the isolated carotid sinus with Rhy 10 μmol·L-1, PS decreased from (19.2±0.3)% to (18.2±0.1)%·kPa-1and the PIV decreased from (219.3±3.3)% to (199.1±3.8)%, while TP and SP increased from (8.2±0.3) to (9.1±0.1)kPa and (21.5±0.1) to (22.1±0.1)kPa, respectively. By perfusing with Rhy 50 and 100 μmol·L-1, the changes in PS, TP and SP were in concentration-dependent manner, and this indicated inhibitory effect of Rhy on CBA. ②Pretreatment with L-NAME 100 μmol·L-1 did not affect inhibitory action of Rhy 50 μmol·L-1 on CBA. ③Pretreatment with TEA 1 mmol·L-1 had no effect on inhibitory effect of Rhy 50 μmol·L-1 on CBA. ④Pretreatment with Bay K8644 500 nmol·L-1 could mostly attenuate effect of Rhy 50 μmol·L-1 on CBA. CONCLUSION Rhy inhibits CBA via blocking calcium influx in baroreceptor nerve ending.
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This study is to evaluate the effect of resveratrol on carotid baroreceptor activity (CBA). The functional curve of carotid baroreceptor (FCCB) was constructed and the functional parameters of carotid baroreceptor were measured by recording sinus nerve afferent discharge in anesthetized male rats with perfused isolated carotid sinus. Resveratrol (30, 60 and 120 μmol·L-1) inhibited CBA, which shifted FCCB to the right and downward. There was a marked decrease in peak slope (PS) and peak integral value (PIV) of carotid sinus nerve charge in a concentration-dependent manner. Pretreatment with Nω-nitro-L-arginine methyl ester (L-NAME, 100 μmol·L-1), an inhibitor of nitric oxide synthase (NOS), eliminated the inhibitory effect of resveratrol. Pretreatment with Bay K8644 (an agonist of L-type calcium channel, 500 nmol·L-1) abolished the effect of resveratrol on CBA. A potent inhibitor of tyrosine phosphatase (sodium orthovanadate, 1 mmol·L-1) did not influence the effect of resveratrol on CBA. Resveratrol inhibits carotid baroreceptor activity, which may be mediated by the locally released NO and decreased calcium influx. Several studies have showed a cardioprotective effect of resveratrol, with the penetrating study of resveratrol, it may show a potential value in the clinical treatment of cardiovascular disease as an alternative medicine.
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AIM To study if cholecystokinin octapeptide (CCK-8) alter cardiovascular functions by its direct inhibitory effect on carotid sinus baroreceptor (CSB) activity. METHODS The functional curve of carotid baroreceptor (FCCB) was constructed and the functional parameters of carotid baroreceptor were measured by recording sinus nerve afferent discharge in anesthetized male rats with perfused isolated carotid sinus. RESULTS ① CCK-8 0.1, 0.5 and 1.0 μmol·L-1 shifted FCCB to the right and downward, with a marked decrease in peak slope and peak integral value of carotid sinus nerve discharge in a concentration-dependent manner, indicating the inhibitory effect of CCK-8 on CSB activity. ② Pretreatment with proglumide (100 μmol·L-1), a nonselective CCK receptor antagonist, or Bay K8644 (0.5 μmol·L-1), an agonist of calcium channel, partially attenuated the inhibitory effect of CCK-8 (0.5 μmol·L-1) on CSB activity. Pretreatment with L-NAME (100 μmol·L-1), an inhibitor of NO synthase, did not affect the inhibitory action of CCK-8. CONCLUSION CCK-8 inhibits CSB activity, which may be mediated by activating CCK receptors in the carotid sinus area and thereby resulting in an inhibition of stretch-sensitive channels and decrease in Ca2+ influx.
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Aim To study the effect of Bay k8644 on cardiac function with the model of myocardial ischemia-reperfusion injury(MIRI)in Rats.Methods Rat MIRI was induced by occluding the left anterior descending coronary artery for 40 min followed by 90 min reperfusion.Eighteen rats were divided randomly into 3 groups: saline,Bay k8644 and 0.1% dimethyl sulfoxide(DMSO)intravenously injected 30 min after ischemia.Heart functions were assessed before ischemia and 5,20 and 40 min after initiation of ischemia and 5,30,60 and 90 min after reperfusion,by measuring heart rate(HR),the left ventricular systolic pressure(LVSP),left ventricular end diastolic pressure(LVEDP) and ?dp/dt_(max).Results After ischemia,LVSP and +dp/dt_(max) decreased(P
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BACKGROUND: Calcium plays a key role in vascular contraction and regulates receptor sensitivity to certain neurotransmitters. Calcium channel blockers are useful in the treatment of both clinical and experimental hypertension. The present study was designed to examine whether there is an alteration of the activity of calcium channels in association with the development of hypertension. METHODS: Deoxycorticosterone acetate(DOCA)-salt hypertension was made by subcutaneous implantation of DOCA(200mg/kg)strip plus saline drinking(1%) and 2-kidney, 1 clip(2KIC)hypertension by clipping the left renal artery with a silver clip(internal gap of 0.2mm). They were used 4 weeks later. Age-matched normal rats served as a control. Mean arterial pressure(MAP) and heart rate(HR) were continuously recorded from the right femoral artery. The drugs were administered intravenously. RESULTS: Vehicle alone was without effect on MAP or HR. In normotensive rats, nifedipine infusion(5 and 10ug/kg/min)caused a dose-dependent decrease in MAP without significant changes in HR, while Bay k 8644(Bay K, 5 and 10 ug/kg/min) increased MAP transiently. Both the depressor response to nifedipine and the pressor response to Bay k were more marked in DOCA-salt hypetensive rats than in normotensive rats. The maximal changes in MAP indced by nifedipine(5 and 50 ug/kg) or Bay K(5 and 50 ug/kg) were also enhanced in 2KIC hypertensive rats as compared with control rats. CONCLUSION: These results indicate that calcium channel inhibitors and activators can affect on the regulation of blood pressure in an opposite fashion. It is also suggested that the activity of calcium channels might be altered in the developement of experimental hypertension.
Subject(s)
Animals , Rats , 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester , Bays , Blood Pressure , Calcium , Calcium Channel Blockers , Calcium Channels , Desoxycorticosterone , Femoral Artery , Heart , Hypertension , Neurotransmitter Agents , Nifedipine , Renal Artery , SilverABSTRACT
BACKGROUND: This study was aimed at defining the varying responses of porcine coronary artery(PCA) to various wavelengths of ultraviolet irradiation, and at relating them to the changes in cyclic GMP contents. METHODS: The ring preparations of PCA with intact or removed endothelium were irradiated with the ultraviolet or visible light of wavelengths(240-520mm) from xenon lamp of a spectrofluorometer, and the changes in vascular tension were recorder on polygraph. For cyclic GMP assay, rat thoracic aorta was frozen after irradiation and homogenated. The supernatant was extracted with water-saturated ether and the cyclic GMP contents were measured with radioimmunoassay. RESULTS: Ultraviolet irradiation relaxed the preparations(UVR-relaxation) in resting state and those precontracted by prostaglandin F2alpha, the maximal relaxation occurring at 410nm, and the magnitude depending on the duration of irradiation. The UVR-relaxation was not affected by removing the endothelium, while it was markedly potentiated by pretreatment with Bay K 8644. The Bay K 8644-induced potentiation of UVR-relaxation was abolished by hemoglobin and slightly reduced by wrapping the rings with aluminum foil. Cyclic GMP contents in the increase was markedly potentiated by pretreatment with Bay K 8644. CONCLUSION: The observations suggest that UVR-relaxation in procine coronary artery is caused by activating the nitric oxide-cyclic GMP system, which is most sensitively activated by UVR of 410nm and that its potentiation induced by Bay K 8644 may be related nitrous substance released from the agent upon UVR.
Subject(s)
Animals , Rats , 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester , Aluminum , Aorta, Thoracic , Bays , Coronary Vessels , Cyclic GMP , Dinoprost , Endothelium , Ether , Light , Passive Cutaneous Anaphylaxis , Radioimmunoassay , Relaxation , Ultraviolet Rays , Vasodilation , XenonABSTRACT
Object To study the effects of SINI TANG (SNT) on the rat aortic rings pre-contracted by high K + and phenylephrine (Phe). Methods The effects of SNT on the aortic rings in the presence of 60 mmol/L KCl and Phe (1?10 -9 -1?10 -4 mmol/L) were observed and t heir me chanisms were studied after treatment with Propranolol (Pro, 3?10 -6 mmol/ L) and Bay K8644 (BK, 1?10 -5 mmol/L) as tool drugs. Results SNT inhibited the contraction induced by cumulative Phe and decreased the maximum tension (T max ); Pro couldn't influe nce the effects of SNT. SNT attenuated the amplitude of contractile effect of hi gh K +; BK couldn't reverse the effects of SNT. Conclusion SNT can shift the dose-response curve to the right and decrease the T max . It shows that SNT is a kind of noncompe titive antagonism. SNT decreases the effect of high K + against contraction of the artery. BK, a L-type Ca 2+ channels activator, couldn't recover the inhibition induced by SNT. The results suggest that SNT inhibit ? 1 recep tor, while calcium channel may not be involved in attenuating the effect of SNT on high K +-induced contraction.