Effect of tetramethyl pyrazine on L-type calcium channel in rat ventricular myocytes

Total alkaloids from the rhizomes of Ligusticum striatum: a review of chemical analysis and pharmacological activities

Rhizome Chuanxiong (RCX), the dried rhizomes of Ligusticum striatum DC., is a geoauthentic TCM herb distributed in Sichuan province of China that possesses efficacy in promoting blood circulation, removing blood stasis and alleviating pain. Rhizome Chuanxiong total alkaloids (RCXTAs) are one of the major characteristic constituents of RCX with the effects of antimigraine, neuroprotective, cardioprotective and other cardiovascular and cerebrovascular diseases. Over the past years, rapid development of technology has advanced some aspects of RCXTAs. The aim of this review is to illustrate the recent advances in the chemical analysis and biological activities of RCXTAs, and to highlight new challenges.

Recent Advances on Nitrones Design for Stroke Treatment

The recent advances of tetramethylpyrazine nitrones and quinolylnitrones for the treatment of stroke have been reviewed and compared with other agents, showing promising therapeutic applications. As a result of a functional transformation of natural product ligustrazine, (Z)-N-tert-butyl-1-(3,5,6-trimethylpyrazin-2-yl)methanimine oxide (6) is a multitarget small nitrone showing potent thrombolytic activity and free radicals scavenging power, in addition to nontoxicity and blood-brain barrier permeability. Similarly, antioxidant (Z)-N-tert-butyl-1-(2-chloro-6-methoxyquinolin-3-yl)methanimine oxide (17) is a novel agent for cerebral ischemia therapy as it is able to scavenge different types of free radical species, showing strong neuroprotection and reduced infarct size.

Animal, Herb, and Microbial Toxins for Structural and Pharmacological Study of Acid-Sensing Ion Channels

Acid-sensing ion channels (ASICs) are of the most sensitive molecular sensors of extracellular pH change in mammals. Six isoforms of these channels are widely represented in membranes of neuronal and non-neuronal cells, where these molecules are involved in different important regulatory functions, such as synaptic plasticity, learning, memory, and nociception, as well as in various pathological states. Structural and functional studies of both wild-type and mutant ASICs are essential for human care and medicine for the efficient treatment of socially significant diseases and ensure a comfortable standard of life. Ligands of ASICs serve as indispensable tools for these studies. Such bioactive compounds can be synthesized artificially. However, to date, the search for such molecules has been most effective amongst natural sources, such as animal venoms or plants and microbial extracts. In this review, we provide a detailed and comprehensive structural and functional description of natural compounds acting on ASICs, as well as the latest information on structural aspects of their interaction with the channels. Many of the examples provided in the review demonstrate the undoubted fundamental and practical successes of using natural toxins. Without toxins, it would not be possible to obtain data on the mechanisms of ASICs' functioning, provide detailed study of their pharmacological properties, or assess the contribution of the channels to development of different pathologies. The selectivity to different isoforms and variety in the channel modulation mode allow for the appraisal of prospective candidates for the development of new drugs.

Tetramethylpyrazine Reduces Epileptogenesis Progression in Electrical Kindling Models by Modulating Hippocampal Excitatory Neurotransmission

Antiepileptic drugs (AEDs) are the primary agents prescribed for clinical management of limbic epilepsy. However, high incidence of pharmacoresistance and a limited armory of drugs for inhibiting the pathological progression of epilepsy pose major obstacles to managing epilepsy. Here, we investigated the effect of tetramethylpyrazine (TMP), the main bioactive alkaloid isolated from the oriental medicine Ligusticum chuanxiong Hort., against the epileptogenesis progression of acute hippocampal and corneal (6 Hz) electrical kindling models of TLE. TMP dose-dependently limited the progression of seizures and reduced the after-discharge duration (ADDs) in a hippocampal mouse kindling model. Mice treated with TMP (20, 50 mg/kg, i.p.) remained in stage 1 of epileptic progression for a protracted period, requiring additional stimulation to induce stages 2-5 epileptic phenotypes. TMP (50 mg/kg) also inhibited 6 Hz corneal kindling progression. In contrast, TMP did not reverse the phenotypes induced in a generalized seizures (GS) model, or the maximal electroshock (MES) or pentylenetetrazole (PTZ)-induced models of epilepsy. Furthermore, patch clamp recordings revealed no effect of TMP (10 μM) on CA1 hippocampal neurons' intrinsic properties but suppressed the (i) frequency of spontaneous excitatory post synaptic currents (sEPSCs), (ii) paired pulse ratio (PPR), and (iii) long-term potentiation (LTP) induction in the Schaffer collateral-CA1 pathway. TMP suppressed the activity of calcium, but not sodium, channels. Taken together, these results suggest that TMP has an antiepileptogenic effect, likely through suppression of excitatory synaptic transmission by its effects on inhibition of calcium channels; these traits distinguish TMP from currently available AEDs. As mice administered TMP did not show any neurologic impairment in the object recognition and open field tests, the data support further development of TMP as a promising treatment for epilepsy.

Chemical analysis of the Chinese liquor Luzhoulaojiao by comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry

Luzhoulaojiao liquor is a type of Chinese liquor that dates back hundreds of years, but whose precise chemical composition remains unknown. This paper describes the screening of the liquor and the identification of its compounds using comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC/TOF-MS). Samples were prepared by both liquid-liquid extraction and solid-phase microextraction, which facilitated the detection of thousands of compounds in the liquor, thus demonstrating the superior performance of the proposed method over those reported in previous studies. A total of 320 compounds were common to all 18 types of Luzhoulaojiao liquor studied here, and 13 abundant and potentially bioactive compounds were further quantified. The results indicated that the high-performance method presented here is well suited for the detection and identification of compounds in liquors. This study also contributes to enriching our knowledge of the contents of Chinese liquors.

Synthesis, biological evaluation, and pharmacokinetic study of novel liguzinediol prodrugs

Liguzinediol (LZDO) ester prodrugs 3-5 were synthesized and evaluated in vitro and in vivo for their potential use in prolonging the half-life of the parent drug LZDO (1a) in vivo. Prodrugs 3-5 were found to display a potent positive inotropic effect on the myocardium, without the risk of arrhythmia. Prodrugs 3-5 rapidly underwent enzymatic hydrolysis to release the parent compound LZDO in 1-3 h in rat liver microsomes and rat plasma. The half-life of the parent compound was prolonged after intragastric administration of prodrug 3, which was found to be a superior prodrug candidate for increasing myocardial contractility.

The effect of ligustrazine on L-type calcium current, calcium transient and contractility in rabbit ventricular myocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Ligustrazine, the biologically active ingredient isolated from a popular Chinese medicinal plant, Ligusticum chuanxiong Hort. (Umbelliferae), has been used effectively to treat ischemic heart diseases, cerebrovascular and thrombotic vascular diseases since the 1970s.

MATERIALS AND METHODS

At present, the effect of ligustrazine on L-type calcium current (I(Ca-L)) of ventricular myocytes remains controversial. In this study, we use the whole-cell patch-clamp techniques and video-based edge detection and dual excitation fluorescence photomultiplier systems to study the effects of ligustrazine on I(Ca-L), and calcium transient and contractility in rabbit ventricular myocytes in the absence and presence of isoprenaline (ISO).

RESULTS

Ligustrazine (5 μM) in low concentration did not affect I(Ca-L) (P>0.05), higher concentrations of this drug (10, 20, 40, 80 μM) inhibited I(Ca-L) in a concentration-dependent manner and reduced I(Ca-L) by 9.6 ± 2.9%, 21.0 ± 4.3%, 33.9 ± 4.3%, and 51.6 ± 7.3%, respectively. Under normal conditions, ligustrazine (40 μΜ) reduced baseline of fura-2 fluorescence intensities (FFI, 340/380 ratio), namely diastolic calcium concentration, changes in FFI (ΔFFI, 340/380 ratio) and maximal velocity of Ca(2+) rise and decay (340/380 ratio/ms) by 6.3%, 26.1%, 25.2%, and 26.5%, and decreased sarcomere peak shorting (PS) and maximal velocity of shorting and relengthening by 36.4%, 31.9%, and 25.0%, respectively. Similarly, ligustrazine (40 μM) reduced baseline FFI, ΔFFI, and maximal velocity of Ca(2+) rise and decay by 14.1%, 51.1%, 35.2%, and 41.1%, and reduced sarcomere PS and maximal velocity of shorting and relengthening by 38.6%, 50.0% and 39.1%, respectively, in the presence of ISO.

CONCLUSIONS

Ligustrazine not only significantly inhibits I(Ca-L) in a concentration-dependent manner but also suppressed calcium transient and contraction in the absence and presence of ISO.

The novel compound liguzinediol exerts positive inotropic effects in isolated rat heart via sarcoplasmic reticulum Ca2+ ATPase-dependent mechanism

AIMS

The present work investigated the underlying mechanism for the positive inotropic effect of liguzinediol (LZDO) in isolated rat hearts.

MAIN METHODS

Isolated rat heart perfusion, intracellular action potential recording, patch clamp and Ca2+ imaging were used to measure the isolated rat heart contractility, action potential duration, L-type Ca2+ current and sarcoplasmic reticulum (SR) Ca2+ transient in rat cardiomyocyte, respectively.

KEY FINDINGS

LZDO (1, 10, and 100μM) significantly enhanced the inotropy of isolated rat hearts, but not heart rates. Nimodipine (1μM, an L-type Ca2+ channel antagonist), ruthenium red (5μM, a ryanodine receptor inhibitor) and thapsigargin (2μM, an irreversible SR Ca2+ ATPase inhibitor) completely blocked the positive inotropic effect of LZDO. LZDO significantly enhanced the intracellular Ca2+ transient in rat cardiomyocyte. However, LZDO (100μM) did not increase L-type Ca2+ channel current. Moreover, LZDO (100μM) restored the depletion effect of caffeine on Ca2+ transient. The following compounds also failed to block the positive inotropic effect of LZDO (100μM): β-AR antagonist (propranolol 1μM), phosphodiesterase (PDE) inhibitor (IBMX 5μM), Na+-K+ ATPase inhibitor (ouabain 1μM), α(1)-AR antagonist (prazosin 1μM), dopamine D1 receptor antagonist (SCH23390 1μM) and Na+-Ca2+ exchange inhibitor (KB-R7943 1μM).

SIGNIFICANCE

The positive inotropic effect of LZDO in isolated rat hearts was mediated through an elevation of SR Ca2+ transient, which may act on SR Ca2+ ATPase. LZDO has a unique biological mechanism that may prove effective in treating heart failure in clinic.

Meta-Analysis of the Clinical Effect of Ligustrazine on Diabetic Nephropathy

Ligustrazine, a bioactive component contained in Chuanxiong (Ligusticum chuanxiong Hort), is widely applied in the treatment of vascular diseases in China, e.g. myocardial and cerebral infarction. The aim of this study was to perform a meta-analysis of randomized controlled trials (RCTs) to evaluate the clinical effect of Ligustrazine on diabetic nephropathy (DN). PUBMED, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), Chinese Biological Medicine Database (CBM), China National Knowledge Infrastructure (CNKI) Database, etc. were searched by computer and manual methods to identify RCTs that were used to evaluate the clinical effect of Ligustrazine on DN patients. Twenty five studies comprising 25 RCTs were involved including 1645 patients (858 in the treatment group and 787 in the control group). The meta-analysis suggests that compared with the control group, Ligustrazine injection has a significant therapeutic effect on improving renal function (blood urea nitrogen [BUN] and serum creatinine [SCr]) and reducing in urine protein (24 h urine protein, urine micro albumin and urinary albumin excretion rate [UAER]) in DN patients.

Novel multi-functional nitrones for treatment of ischemic stroke

Ischemic stroke resulting from obstruction of blood vessels is an enormous public health problem with urgent need for effective therapy. The co-administration of thrombolytic/antiplatelet agent and neuroprotective agent improves therapeutic efficacy and agent possessing both thrombolytic/antiplatelet and antiradical activities provides a promising strategy for the treatment of ischemic stroke. We have previously reported a novel compound, namely TBN, possessing both antiplatelet and antiradical activities, showed significant neuroprotective effect in a rat stroke model. We herein report synthesis of a series of new pyrazine derivatives, and evaluation of their biological activities. Their mechanisms of action were also investigated. Among these new derivatives, compound 21, armed with two nitrone moieties, showed the greatest neuroprotective effects in vitro and in vivo. Compound 21 significantly inhibited ADP-induced platelet aggregation. In a cell free antiradical assay, compound 21 was the most effective agent in scavenging the three most damaging radicals, namely (·)OH, O(2)(·-) and ONOO(-).

Ligustrazine inhibits lipopolysaccharide-induced proliferation by affecting P27, Bcl-2 expression in rat mesangial cells

Ligustrazine has a renoprotective effect against nephritis. In the present study, we investigated the roles of ligustrazine on lipopolysaccharide-induced changes of proliferation, cell cycle in cultured rat mesangial cells. 3-(4,5-dimethyltiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay revealed that rat mesangial cells treated with lipopolysaccharide (10mg/l) underwent significant proliferation compared with control group. This effect was significantly inhibited by ligustrazine (400 to 2500 mg/l). Flow cytometric analysis revealed that cells treated with lipopolysaccharide showed significant reduction in the ratio of G0/G1 phase and significant elevation in the ratio of S+G2/M phase. The changes of cell cycle induced by lipopolysaccharide were reversed by ligustrazine. In addition, lipopolysaccharide suppressed P27 protein expression was significantly increased by ligustrazine (100, 500, 2500 mg/l). Moreover, rat mesangial cells treated with lipopolysaccharide showed scanty apoptosis with up-regulation of Bcl-2expression, while Bax protein expression was not changed. Ligustrazine (100, 500, 2500 mg/l) significantly reversed lipopolysaccharide-induced up-regulation of Bcl-2 protein and increased apoptotic cell death. In summary, ligustrazine displayed a significant inhibiting effect on lipopolysaccharide-induced proliferation through increasing P27 and decreasing Bcl-2 protein expression in rat mesangial cells.

Synthesis and preliminary evaluation of neuroprotection of celastrol analogues in PC12 cells

A series of celastrol analogues were synthesized, and their neuroprotective effect against t-BHP-induced cytotoxicity was investigated in neuronal PC12 cells. Their effects on Hsp70 protein expression were quantified by Western blot analysis. The study found that compound CL12 is more effective than the parent celastrol against t-BHP-induced cytotoxicity. CL12 up-regulates Hsp70 protein expression dose-dependently. These results suggest that CL12 is a potential candidate for the intervention of neurodegenerative diseases.

Protective effects of ligustrazine on cisplatin-induced oxidative stress, apoptosis and nephrotoxicity in rats

Cisplatin is an effective agent against various solid tumors. However, its nephrotoxicity been reported to be a dose-limiting factor for treating various types of tumors. The aim of this study was to determine the protective effects of ligustrazine on cisplatin-induced nephrotoxicity through tissue oxidant/antioxidant parameters, light microscopic evaluation, and tubular apoptosis in rats. Ligustrazine was administered in doses of 50 and 100mg/kg/day intraperitoneally (i.p.), for 7 consecutive days, starting 2 days before a single intraveneous dose of cisplatin (8mg/kg). Results revealed that treatment with cisplatin alone caused significant changes in the levels of urinary protein, urinary N-acetyl-beta-d-glucosaminidase, serum creatinine, blood urea nitrogen, and kidneys histopathological damages. All the aforementioned changes were effectively attenuated by ligustrazine. In addition, cisplatin caused increases in the levels of malondialdehyde, nitric oxide, nitric oxide synthase and decreases in the levels of reduced glutathione, glutathione-S-transferase, superoxide dismutase. These changes were restored to near normal levels by ligustrazine at 100mg/kg. In conclusion, ligustrazine has dose dependent protective effects against cisplatin-induced renal tubular toxicity.

Design, synthesis, and biological activities of novel Ligustrazine derivatives

A series of novel Ligustrazine derivatives was designed, synthesized, and assayed for their protective effects on damaged ECV-304 cells and antiplatelet aggregation activities. The results showed that most Ligustrazine derivatives exhibited lower EC(50) values for protective effects on the ECV-304 cells damaged by hydrogen peroxide in comparison with Ligustrazine. And some Ligustrazine derivatives presented better antiplatelet aggregation activities than Ligustrazine. The derivatives containing the bisphenylmethyl pharmacophore (7a-c) exhibited highest potency. Compound 7a displayed most potential protective effects on the ECV-304 cells damaged by hydrogen peroxide, and compound 7c was found to be the most active antiplatelet aggregation agent. Structure-activity relationships were briefly discussed.

Protective effect of ligustrazine on accelerated anti-glomerular basement membrane antibody nephritis in rats is based on its antioxidant properties

Ligustrazine has a renoprotective effect against nephritis. In this study, we further characterized the renoprotective properties of ligustrazine in an experimental model using accelerated anti-glomerular basement membrane antibody (AGBM-Ab). Ligustrazine was given i.p. once daily at 50, 100 mg/kg for 15 days after singly giving i.v. of rabbit anti-rat glomerular basement membrane serum, and showed dose-dependent inhibition the elevation of urinary protein, serum creatinine and blood urea nitrogen as well as the development of glomerular histological changes. Ligustrazine (50 mg/kg) had no affect on glutathione (GSH) content, glutathione peroxidase and catalase activities, but decreased the malondialdehyde (MDA) content and increased superoxide dismutase (SOD) activity in nephritis induced by AGBM-Ab. Ligustrazine (100 mg/kg) significantly decreased MDA content while significantly increased GSH content and SOD, glutathione peroxidase, catalase activities of kidney tissues in the rats treated with AGBM-Ab alone. In conclusion, our results show that ligustrazine has protective activity against accelerated AGBM-Ab nephritis, and its renoprotective effect may be due to its antioxidant properties and inhibition reactive oxygen species (ROS).

Ligustrazine attenuates acute myocardium injury after thermal trauma

This study was designed to investigate the effects of ligustrazine on burn-induced myocardiac injury as well as TNF-alpha levels in severely burned rats. Sprague-Dawley rats were divided into four groups: (1) sham group, rats who underwent sham burn; (2) fluid-resuscitated sham group (FRsham), rats who underwent sham burn, and lactated Ringer's solution for resuscitation; (3) control group, rats given third-degree burns over 30% total body surface area (TBSA) and lactated Ringer's solution for resuscitation; (4) ligustrazine group, rats given burn and lactated Ringer's solution with ligustrazine inside for resuscitation. Myocardial injury was assessed at 6h after burn by detecting serum levels of creatine kinase MB fraction (CK-MB) and lactate dehydrogenase (LDH), as well as water content, histological score, and ultrastructure change of cardiac tissue. In addition, myocardium ATP content was analyzed. Enzyme-linked immunosorbent assay (ELISA) was used to examine cardiac tumor necrosis factor-alpha (TNF-alpha) levels. The results showed that burn trauma resulted in the increasing serum LDH and CK-MB, elevated myocardial water content, aggravated myocardial histological and ultrastructural lesions, increased myocardium ATP, and serum TNF-alpha. Ligustrazine 10mg/kg iv markedly inhibited increases in serum CK-MB and LDH, reduced myocardial water content from 76.91+/-0.19% in control group to 75.40+/-0.57%, significantly decreased the histologic scores of myocardium, and mollified the ultrastructural damage in cardiac myocytes. Ligustrazine significantly attenuated elevations in serum TNF-alpha level and myocardial ATP quantity. Therefore, our results demonstrate that ligustrazine exhibits significant protective effects on burn-induced myocardial injury via inhibiting the release of TNF-alpha and improving utilization of ATP.

Effect of Ligustrazine on liver injury after burn trauma

This study was designed to investigate the effect of Ligustrazine on burn-induced liver injury as well as the activation of nuclear factor kappaB (NF-kappaB) in severely burned rats. Sprague-Dawley rats were divided into three groups: (1) sham group, rats who underwent sham burn; (2) control group, rats given third-degree burns over 30% total body surface area (TBSA) and lactated Ringer solution for resuscitation; (3) Ligustrazine group, rats given burn and lactated Ringer's solution with Ligustrazine inside for resuscitation. Liver injury was assessed at 24 h post-burn by serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT), as well as liver wet/dry weight ratio. Liver myeloperoxidase (MPO) activity was also analyzed. Hepatic NF-kappaB activity was examined by electrophoretic mobility shift assay (EMSA). Burn results in hepatic dysfunction and increased hepatic NF-kappaB activity, elevated liver wet/dry ratio and hepatic MPO activity. Ligustrazine inhibited these changes and alleviated burn-mediated hepatic dysfunction. The data indicated that Ligustrazine has a protective effect on burn-induced liver injury and possible mechanism may be attributed to its inhibitory action on the activation of NF-kappaB following burn trauma.

Tetramethylpyrazine elicits disparate responses in cardiac contraction and intracellular Ca(2+) transients in isolated adult rat ventricular myocytes

Tetramethylpyrazine (TMP) is the biologically active ingredient isolated from a popular Chinese medicinal plant, Ligusticum wallichil franchat, which has been used effectively since the 1970s to treat ischemic heart disease, cerebrovascular and thrombotic vascular diseases. The direct action of TMP on cardiac contractile function, however, is largely unclear. This study was designed to examine the effect of TMP on ventricular contractile function at the single cardiac myocyte level. Adult rat ventricular myocytes were isolated and stimulated to contract at 0.5 Hz, and mechanical and intracellular Ca(2+) properties were evaluated using an IonOptix Myocam system. Contractile properties analyzed included peak shortening (PS), time-to-peak shortening (TPS), time-to-90% relengthening (TR(90)), maximal velocity of shortening/relengthening (+/-dl/dt), resting intracellular Ca(2+) level, Ca(2+)-induced Ca(2+) release (CICR) and decay. TMP (10(-10)-10(-5) M) exhibited an increase in PS with a maximal increase of 30.9%. TMP had no effect on +/-dl/dt, TPS/TR(90) or CICR but lowered resting intracellular Ca(2+) level and slowed intracellular Ca(2+) decay. Pretreatment with either the nonspecific nitric oxide synthase (NOS) inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME, 100 microM) or inducible NOS inhibitor W1400 effectively abolished the positive effect of TMP on myocyte shortening. Our data demonstrate a direct positive inotropic effect of TMP in cardiac myocytes, which may be related, at least in part, to NO production.

Adult rat cardiomyocytes exhibit capacitative calcium entry

Capacitative Ca(2+) entry (CCE) refers to the influx of Ca(2+) through plasma membrane channels activated on depletion of endoplasmic-sarcoplasmic reticulum Ca(2+) stores. We utilized two Ca(2+)-sensitive dyes (one monitoring cytoplasmic free Ca(2+) and the other free Ca(2+) within the sarcoplasmic reticulum) to determine whether adult rat ventricular myocytes exhibit CCE. Treatments with inhibitors of the sarcoplasmic endoplasmic reticulum Ca(2+)-ATPases were not efficient in releasing Ca(2+) from stores. However, when these inhibitors were coupled with either Ca(2+) ionophores or angiotensin II (an agonist generating inositol 1,4,5 trisphosphate), depletion of stores was observed. This depletion was accompanied by a significant influx of extracellular Ca(2+) characteristic of CCE. CCE was also observed when stores were depleted with caffeine. This influx of Ca(2+) was sensitive to four inhibitors of CCE (glucosamine, lanthanum, gadolinium, and SKF-96365) but not to inhibitors of L-type channels or the Na(+)/Ca(2+) exchanger. In the whole cell configuration, an inward current of approximately 0.7 pA/pF at -90 mV was activated when a Ca(2+) chelator or inositol (1,4,5)-trisphosphate was included in the pipette or when Ca(2+) stores were depleted with a Ca(2+)-ATPase inhibitor and ionophore. The current was maximal at hyperpolarizing voltages and inwardly rectified. The channel was relatively permeant to Ca(2+) and Ba(2+) but only poorly to Mg(2+) or Mn(2+). Taken together, these data support the existence of CCE in adult cardiomyocytes, a finding with likely implications to physiological responses to phospholipase C-generating agonists.

Effect of tetramethylpyrazine on exocrine pancreatic and bile secretion

AIM: To investigate the effect of tetramethylpyrazine (ligustrazine, TMP) on the secretion of exocrine pancreas (and biliary).

METHODS: In in vivo study, we investigated the effect of TMP on the secretion of pancreatic-bile juice (PBJ) in rats. Using human pancreatic duct cell line, CAPAN-1, combined with the short-circuit current (I_SC) technique we further studied the effect of TMP on the pancreatic anion secretion.

RESULTS: Administration of TMP (80 mg/kg, ip) significantly increased the secretion of PBJ (P < 0.05), but the pH of PBJ and the secretion of pancreatic protein were not significantly affected. Basolateral addition of TMP produced a dose-dependent increase in I_SC (EC₅₀ = 1.56 mmol/L), which contained a fast transient I_SC response followed by a slow decay. Apical application of Cl^- channel blockers, DPC (1 mmol/L), decreased the response by about 67.1% (P < 0.001), whereas amiloride (100 μmol/L), a epithelial sodium channel blockers, had no effect. Removal of extracellular HCO₃^- abolished TMP-induced increase in I_SC by about 74.4% (P < 0.001), but the removal of external Cl^- did not. Pretreatment with phosphodiesterase inhibitor, IBMX (0.5 mmol/L), decreased the TMP-induced I_SC by 91% (P < 0.001).

CONCLUSION: TMP could stimulate the secretion of PBJ, especially pancreatic ductal HCO₃^- secretion via cAMP or cGMP-dependent pathway. It need further study to investigate the roles of cAMP or cGMP in the effect of TMP on the secretion of exocrine pancreas.

Effect of tetramethylpyrazine on P-selectin and hepatic/renal ischemia and reperfusion injury in rats

AIM: To investigate the effect of tetramethylpyrazine on hepatic/renal ischemia and reperfusion injury in rats.

METHODS: Hepatic/renal function, histopathological changes, and hepatic/renal P-selectin expression were studied with biochemical measurement and immunohistochemistry in hepatic/renal ischemia and reperfusion injury in rat models.

RESULTS: Hepatic/renal insufficiency and histopathological damage were much less in the tetramethylpyrazine-treated group than those in the saline-treated groups. Hepatic/renal P-selectin expression was down regulated in the tetramethylpyrazine-treated group.

CONCLUSION: P-selectin might mediate neutrophil infiltration and contribute to hepatic/renal ischemia and reperfusion injury. Tetramethylpyrazine might prevent hepatic/renal damage induced by ischemia and reperfusion injury through inhibition of P-selectin.

Mechanisms responsible for the in vitro relaxation of ligustrazine on porcine left anterior descending coronary artery

In this study, we have evaluated the underlying mechanisms responsible for the relaxation response of ligustrazine (2,3,5,6-tetra-methyl-pyrazine; 2,3,5,6-MP) and its structural analogues (2-methyl-pyrazine (2-MP); ethyl-pyrazine (EP); 2,3-di-methyl-pyrazine (2,3-MP); 2,5-di-methyl-pyrazine (2,5-MP); 2,6-di-methyl-pyrazine (2,6-MP) and 2,3,5-tri-methyl-pyrazine (2,3,5-MP)) in porcine left anterior descending coronary artery (tertiary branch, O.D. </=1 mm). In 5-hydroxytryptamine (3 microM) precontracted preparations, cumulative administration (0.1-300 microM) of all pyrazine analogues caused an endothelium-independent, concentration-dependent relaxation. The relative inhibitory potency, as compared at concentration with which 50% relaxation occurred, was 2,3,5,6-MP>2,3,5-MP>EP>2,5-MP>/=2,6-MP>/=2,3-MP>2-MP. Besides, salbutamol and forskolin caused an endothelium-independent relaxation. The relaxation response of ligustrazine, salbutamol and forskolin was blunted in the presence of cis-N-(2-phenylcyclopentyl) azacyclotridec-1-en-2-amine (MDL 12330A) (10 microM, an adenylate cyclase inhibitor) and N-[2-((bromocinnamyl)amino)ethyl]-5-isoquinoline-sulphonamide (H-89, a protein kinase A inhibitor, 3 microM). Patch-clamp, whole-cell electrophysiological studies using single smooth muscle cells of the left anterior descending coronary artery revealed that ligustrazine (300 microM), salbutamol (30 microM) and forskolin (1 microM) inhibited the nifedipine-sensitive L-type Ca(2+) channels, and the inhibitory effect was eradicated by MDL 12330A (10 microM) and H-89 (1 microM). However, neither the Ca(2+)-dependent K(+) channel nor the ATP-dependent K(+) channel was modified by ligustrazine (300 microM). In conclusion, our results indicate that ligustrazine-mediated left anterior descending coronary artery relaxation is due to the activation of adenylate cyclase/protein kinase A cascade and the subsequent inhibition of nifedipine-sensitive, voltage-dependent L-type Ca(2+) channels. However, opening of K(+) channels seems to play no role in mediating the relaxation effect of ligustrazine.