Meta-Analysis of the Factors Influencing the Restoration of Spontaneous Circulation After Cardiopulmonary Resuscitation.

Objective: This study aimed to systematically evaluate the factors influencing the restoration of spontaneous circulation (ROSC) after cardiopulmonary arrest (CA). Methods: Relevant papers on the factors influencing the ROSC in patients with CA were retrieved from PubMed, Embase, Cochrane Library, China Biology Medicine disk, China National Knowledge Infrastructure, Wanfang, and VIP databases. After screening, data extraction, and quality evaluation of the papers, a meta-analysis was carried out. Results: A total of 36 papers, involving a total sample size of 2,305 cases, were included. The meta-analysis revealed that the location and time of onset of CA, the type of cardiac rhythm at first monitoring, the start time of cardiopulmonary resuscitation (CPR), the use of electric defibrillation, and the cumulative dose of adrenaline all significantly impacted the ROSC (p < 0.05) and may have affected its success rate. The pH value at CA onset, combined use of adrenaline and vasopressin, CPR duration, mechanical cardiac compression use, and whether CA was caused by heart disease had no significant effect on ROSC. Conclusion: The location and time of onset of CA, the cardiac rhythm at first monitoring, the start time of CPR, the use of electric defibrillation, and the cumulative dose of adrenaline significantly impacted the ROSC.

[Effects of Cathepsin K on spatial learning and memory in rats].

OBJECTIVE: To investigate the effects of Cathepsin K(CatK) on spatial learning and memory in rat hippocampus and its mechanisms. METHODS: Twenty male SD rats were randomly divided into Control group and CatK inhibitor group(CatKⅡ group), which were microinjected with Cathepsin K specific inhibitor(0.5 µg/µl) and artificial cerebrospinal fluid in hippocampal DG area respectively with 5 days. The cultured hippocampal neuron cells were divided into control group (CON group), negative control group(NC group), siRNA interference group(siCatK group). Three re-wells were set for each group, and samples were collected 18～20 h after siRNA transfection. Morris water maze was used to evaluate spatial learning and memory function of rats. Meanwhile, dynamic changes of glutamate(Glu) content in extracellular fluid of DG region during learning and memory were observed by microdialysis and high performance liquid chromatography in conscious rats. Western blot was used to detect CatK-mediated Notch1 activation and other signal molecules. RESULTS: Animal experiments showed that compared with the control group, the spatial learning and memory ability were decreased significantly in CatKII group, and the hippocampus protein expressions of c-Notch1, p-Akt, p-CREB and BDNF were also decreased significantly(P＜0.05); the levels of Glu in DG area of control group and CatK II group were increased significantly with Morris water maze training days, but the increase of CatK II group was significantly weaker than that of control group(P＜ 0.05). The results of cell experiment showed that the expressions of CatK, c-Notch1, p-CREB and BDNF in siCatK group were significantly lower than other groups (P＜0.05). CONCLUSION: CatK can affect the spatial learning and memory function of rats by activating Notch1 and its memory related signal protein in hippocampus.

Clinical Inertia and 2-Year Glycaemic Trajectories in Patients with Non-Newly Diagnosed Type 2 Diabetes Mellitus in Primary Care: A Retrospective Cohort Study.

OBJECTIVE: To analyse diabetes treatment, treatment change and self-management behaviours in association with 2-year glycaemic trajectories in patients with non-newly diagnosed type 2 diabetes mellitus in Chinese primary care. METHODS: This was an observational, multi-centre, longitudinal, retrospective cohort study. Clinical data of 4690 subjects were extracted from electronic medical records, including serial glycated haemoglobin A1c (HbA1c) measurements, antidiabetic medication records and compliance to exercise, diet, medications and self-monitoring of blood glucose (SMBG). Patterns of longitudinal HbA1c trajectories were identified using the percentage of HbA1c measurements <7.5% from the second available HbA1c measurement. Clinical relevance of the clusters was assessed through multivariable analysis. RESULTS: Approximately half of the participants demonstrated good glycaemic control; of these, 34.5% demonstrated stable, good control, and 13.7% demonstrated relatively good control. About 16.2% demonstrated moderate control, and 35.6% demonstrated poor control. From the good to poor control groups, the percentage of subjects treated with insulin at baseline and during the follow-up period increased gradually, while the percentage of subjects adhering to exercise, diet, medications and SMBG decreased gradually. Compared with baseline, the adherence to exercise, diet, medications and SMBG improved significantly. Approximately 50% and 26% of subjects in the two poorest control groups, respectively, experienced treatment changes. After multivariable adjustments, baseline HbA1c ≥7.5%, HbA1c change ≥-0.5% from baseline to visit 1, insulin treatment, treatment change, poor adherence to diet, exercise, SMBG during the follow-up period and HbA1c measurements <3 per year were significantly associated with poorer glycaemic control. CONCLUSION: We identified four longitudinal HbA1c trajectories in patients with non-newly diagnosed type 2 diabetes. Even if baseline HbA1c is suboptimal, aggressive treatment changes, good adherence during the follow-up period, ≥3 HbA1c measurements per year and reducing HbA1c levels to a certain extent by the first follow-up visit were important for good, stable, long-term glycaemic control.

An outbreak of epidemic keratoconjunctivitis caused by human adenovirus type 8 in primary school, southwest China.

BACKGROUND: Two outbreaks of epidemic keratoconjunctivitis (EKC) occurred successively with an interval of 5 days in two primary boarding schools in Weixi Lisu Autonomous County, Diqing, and Tibetan Autonomous Prefecture, Yunnan. The aims of this study were to determine the intensity and characteristics of the outbreaks, as well as the clinical manifestations in the patients, the risk factors for infection and the pathogen responsible for the two outbreaks. METHODS: An outbreak investigation was conducted in two primary schools, and a case-control study including patients from the Weixi County Ethnic Primary School was performed. Relevant specimens were collected according to the case definition, and next-generation sequencing was employed to identify the pathogen. An epidemiological investigation method was used to analyse the related epidemiological characteristics, such as risk factors. The phylogenetic tree was constructed by MEGA 7.0. RESULTS: A total of 331 acute conjunctivitis cases, including probable cases of EKC, were reported in the two schools, and the attack rates were 30.59% (171/559, 95%CI: 26.76-34.42) and 20.41% (160/784, 95%CI: 17.58-23.24), respectively. Cases occurred in all grades and classes in both schools, and only one staff member in each school presented illness. The epidemics lasted for 54 days and 45 days, respectively. The patients had typical manifestations of EKC, such as acute onset, follicular hyperplasia, pseudomembrane formation, preauricular lymphadenopathy, corneal involvement and blurred vision, and a relatively long disease course (average 9.40 days, longest 23 days and shortest 7 days). The risk factor for infection was close contact with a patient or personal items contaminated by a patient. The pathogen responsible for the outbreaks was HAdV-8. The virus was highly similar to the 2016 HAdV-8 strain from Tibet, China. CONCLUSIONS: This study strongly suggests that HAdV-8 could lead to serious consequences. This is the second report of a HAdV-8-associated EKC outbreak in mainland China. Tibetan HAdV-8 might be circulating in southwest China; therefore, it is necessary to monitor the pathogens causing acute conjunctivitis in this area.

Role of peripheral vestibular receptors in the control of blood pressure following hypotension.

Hypotension is one of the potential causes of dizziness. In this review, we summarize the studies published in recent years about the electrophysiological and pharmacological mechanisms of hypotension-induced dizziness and the role of the vestibular system in the control of blood pressure in response to hypotension. It is postulated that ischemic excitation of the peripheral vestibular hair cells as a result of a reduction in blood flow to the inner ear following hypotension leads to excitation of the central vestibular nuclei, which in turn may produce dizziness after hypotension. In addition, excitation of the vestibular nuclei following hypotension elicits the vestibulosympathetic reflex, and the reflex then regulates blood pressure by a dual-control (neurogenic and humoral control) mechanism. In fact, recent studies have shown that peripheral vestibular receptors play a role in the control of blood pressure through neural reflex pathways. This review illustrates the dual-control mechanism of peripheral vestibular receptors in the regulation of blood pressure following hypotension.

Ghrelin attenuates ultraviolet B radiation-induced impairment in capacities of epidermal stem cells.

Persistent exposure to solar ultraviolet radiation (UVR) causes continuous damages to skin, including progressive impairment of epidermal stem cells (ESCs) capacities. Ghrelin is the only known endogenous orexigenic hormone, which has displayed its various pharmacological functions. In the current study, we found that the specific receptor of ghrelin, growth hormone secretagogue receptor (GHS-R), is expressed in ESCs. Interestingly, GHS-R expression is significantly upregulated in response to ultraviolet B (UVB) radiation. We also found that ghrelin treatment prevented UVB radiation-induced reduction in cell viability and the release of lactate dehydrogenase (LDH). Additionally, ghrelin reduced UVB radiation-induced generation of reactive oxygen species (ROS) and restored the intracellular level of reduced glutathione (GSH). UVB radiation significantly suppressed the expressions of integrin ß1 and Krt19, the two major ESC markers, which were restored by ghrelin. Notably, knockdown of GHS-R abolished the effects of ghrelin on the expressions of integrin ß1 and Krt19, suggesting the involvement of GHS-R. Also, we found that ghrelin treatment inhibited UVB radiation- induced reduction of Wnt1, Wnt3a, Myc, and cyclin D1 at both the mRNA levels and the protein levels. Taken together, our findings identify a novel function of ghrelin on maintaining the capacities of ESCs against UVB radiation.

[Long-term results of personalized treatment in 72 breast cancer patients who failed chemotherapy].

OBJECTIVE: To evaluate the efficacy and prognostic factors of personalized treatment for breast cancer patients who failed chemotherapy. METHODS: Seventy-two patients with breast cancer who failed chemotherapy were treated at the Tumor Hospital of Harbin Medical University from January 2001 to January 2012. Among them, 42 cases received 5.6 cycles (range, 4-8 cycles) of postoperative adjuvant chemotherapy, and 30 cases received 12.2 cycles (range, 6-22 cycles), both postoperative adjuvant and salvage chemotherapy. All of the 72 patients of stage IV were given personalized treatment. Under guidance of the principle that multidisciplinary treatment improves control rate but does not or less damage the normal tissues and host immune function, precise radiotherapy combined with Chinese herbal medicine (CHM), biological agent and others were chosen for the patients. RESULTS: The median survival time was 20 months. Univariate analysis showed that non-invasive ductal carcinoma, less metastasized organs, without brain, liver and lung metastasis, Karnofsky performance scores ≥ 80, not combined with chemotherapy, and multiple courses of Chinese herbal medicine and biolojical agent treatment had significant impact on survival (P < 0.05). Multivariate analysis showed that no brain metastasis, non-invasive ductal carcinoma, and Chinese herbal medicine and biological agent treatment ≥ 7 courses and not combined with chemotherapy had obvious significance (P < 0.05). The rate of grade 3 and 4 treatment-related hematological toxicity was 8.3% (6/72) and 5.6% (4/72), respectively. All the patients with grade 4 hematological toxicity were the cases of grade 3 at hospital admission. No grade 3 and 4 acute radiation damages of the lung and liver were noticed. CONCLUSION: Chinese herbal medicine combined with biological agents and others prolongs survival time in breast cancer patients who failed chemotherapy, and provides an alternative treatment modality for them.

Mechanism of glutamate receptor for excitation of medial vestibular nucleus induced by acute hypotension.

In the vestibular nuclei, acute hypotension induces excitation of electrical activity and expression of c-Fos protein and phosphorylated extracellular signal-regulated kinase (pERK). Expression of c-Fos protein and pERK is mediated by the excitatory neurotransmitter, glutamate. We investigated the signaling pathway of glutamate and its receptors in the vestibular nuclei following acute hypotension in conscious rats. Glutamate release and the expression of c-Fos protein in the medial vestibular nuclei (MVN) were measured by microdialysis and immunohistochemical analysis, respectively. We compared the responses of rats with unilateral labyrinthectomy to unaltered controls. Acute hypotension was induced by infusing sodium nitroprusside (SNP) into the femoral vein. In the control group, glutamate release and the expression of c-Fos protein increased in the bilateral MVN following acute hypotension. In the unilateral labyrinthectomy group, glutamate release and the expression of c-Fos protein increased in the MVN contralateral to the lesion, but did not change in the ipsilateral MVN following acute hypotension. Microinjection of NMDA or AMPA into the lateral ventricle increased the expression of c-Fos protein in the bilateral MVN of conscious intact labyrinthine rats. However, after intracerebroventricular microinjection of MK-801 or CNQX little c-Fos protein was expressed in the bilateral MVN of these rats following acute hypotension. These results suggest that in response to acute hypotension, excitatory afferent signals from the peripheral vestibular receptors release glutamate into postsynaptic neurons in the vestibular nuclei. These excitatory signals are transmitted through the NMDA receptors and AMPA receptors of glutamate in the vestibular system.

Changes of some amino acid concentrations in the medial vestibular nucleus of conscious rats following acute hypotension.

Microdialysis and high performance liquid chromatography (HPLC) were used to measure the changes of certain amino acids in the medial vestibular nucleus (MVN) of conscious rats in order to understand whether those amino acids are involved in the regulation of blood pressure. Acute hypotension was induced by infusing sodium nitroprusside (SNP) into the femoral vein. In the control group, glutamate (Glu) release increased, though gamma-aminobutyric acid (GABA) and taurine (Tau) release decreased in the MVN following acute hypotension. In the unilateral labyrinthectomy group, the levels of Glu, GABA, and Tau were unchanged in the ipsilateral MVN to the lesion following acute hypotension. Furthermore, in the contralateral MVN to the lesion, Glu release increased, and GABA and Tau release decreased following acute hypotension. These results suggest that SNP-induced acute hypotension can influence the activity of neurons in the MVN through afferent signals from peripheral vestibular receptors, and that certain amino acid transmitters in the MVN are involved in this process.

[Changes of gamma-aminobutyric acid and glycine released in the medial vestibular nucleus following acute hypotension in conscious rats].

To understand whether some amino acids in the medial vestibular nucleus (MVN) of conscious rats are involved in the regulation of blood pressure, microdialysis technique and high performance liquid chromatography (HPLC) were used to measure the changes of gamma-aminobutyric acid (GABA) and glycine (Gly) in this central area. Wistar rats (250-350 g) were randomly divided into three experimental groups: the control group with intact labyrinths; the ipsilateral MVN of unilateral labyrinthectomy (UL); contralateral MVN of the UL. Acute hypotension was induced by intravenous infusion of sodium nitroprusside (SNP). Unilateral chemical labyrinthectomy was performed 14 days before the start of the experiment to eliminate afferent signals from the peripheral vestibular receptors in the inner ear. Blood pressure decreased by 30% after SNP injection. In the control group, GABA and Gly release reduced to 43.53%+/-6.58% (P<0.01) and 62.24%+/-7.51% (P<0.01) respectively in the MVN following SNP-induced acute hypotension in conscious rats. In the contralateral MVN of UL, GABA and Gly release also reduced to 45.85%+/-17.27% (P<0.01) and 73.30%+/-3.00% (P<0.01) respectively following SNP-induced acute hypotension in conscious rats. In contrast, in the ipsilateral MVN of UL, GABA and Gly releases were not changed following SNP-induced acute hypotension in conscious rats. These results suggest that the SNP-induced acute hypotension may influence the activity of the neurons in the MVN by the afferent impulses from the peripheral vestibular organ, and that GABA and Gly may be involved in this process.

Natriuretic peptide-dependent cGMP signal pathway potentiated the relaxation of gastric smooth muscle in streptozotocin-induced diabetic rats.

A common gastrointestinal complication of diabetes is gastroparesis, and patients with gastroparesis may present with early satiety, nausea, vomiting, bloating, postprandial fullness, or upper abdominal pain. However, the pathogenesis is not clear yet. A recent study indicated that atrial natriuretic peptide (ANP) was secreted from the gastric mucosa and the ANP family plays an inhibitory role in the regulation of gastrointestinal motility, but the effect of the natriuretic peptide signal pathway on diabetic gastroparesis has not been reported. The study investigated the effect of C-type natriuretic peptide (CNP) particulate guanylyl cyclase (pGC) cyclic guanosine monophosphate (cGMP) signaling on gastroparesis in streptozotocin (STZ)-induced diabetic rats. Male Sprague-Dawley rats were divided into two groups; group I: normal control rats; group II: STZ-induced diabetic rats; 4 weeks after induction, the experiments were performed. The spontaneous contraction of gastric smooth muscle strips was recorded by using physiographs in control and diabetic rats. The pGC activity in response to CNP and cGMP production in gastric smooth muscle were measured by using radioimmunoassay (RIA) in normal and diabetic rats. CNP induced a longer lasting relaxation of gastric antral circular smooth muscle strips in STZ-induced diabetic rats. The inhibitory effect of CNP on spontaneous contraction revealed a dose-dependency, and the inhibitory percentages were 25.5 +/- 1.7%, 43.6 +/- 3.2%, 85.1 +/- 2.5% in diabetic rats and 20.5 +/- 1.5%, 31.1 +/- 1.7%, 58.9 +/- 3.7% in the control group at the concentrations of 0.01, 0.03, and 0.1 mumol/l, respectively. The cGMP production and pGC activity in response to CNP in gastric muscle tissues were significantly potentiated in STZ-induced diabetic rats. Natriuretic peptide receptor type B (NPR-B) gene was expressed in the gastric smooth muscles of normal and diabetic rats, and the expression was increased in diabetic rats. The results suggest that natriuretic peptide-dependent pGC-cGMP signal is upregulated and may contribute to diabetic gastroparesis in STZ-induced diabetic rats.

C-type natriuretic-peptide-potentiated relaxation response of gastric smooth muscle in streptozotocin-induced diabetic rats.

AIM: To study the sensitivity of gastric smooth muscle to C-type natriuretic peptide (CNP) in streptozotocin (STZ)-induced diabetic rats. METHODS: The spontaneous contraction of a gastric smooth muscle strip was recorded by using physiological methods in rats. The expressions of CNP and natriuretic peptide receptor-B (NPR-B) in gastric tissue were examined by using immunohistochemistry techniques in the diabetic rat. RESULTS: At 4 wk after injection of STZ and vehicle, the frequency of spontaneous contraction of gastric smooth muscle was significantly reduced in diabetic rats, and the frequency was decreased from 3.10 +/- 0.14 cycle/min in controls to 2.23 +/- 0.13 cycle/min (n = 8, P < 0.01). However, the amplitude of spontaneous contraction was not significant different from the normal rat. CNP significantly inhibited spontaneous contraction of gastric smooth muscle in normal and diabetic rats, but the inhibitory effect was significantly potentiated in the diabetic rats. The amplitudes of spontaneous contraction were suppressed by 75.15% +/- 0.71% and 58.92% +/- 1.32% while the frequencies were decreased by 53.33% +/- 2.03% and 26.95% +/- 2.82% in diabetic and normal rats, respectively (n = 8, P < 0.01). The expression of CNP in gastric tissue was not changed in diabetic rats, however the expression of NPR-B was significantly increased in diabetic rats, and the staining indexes of NPR-B were 30.67 +/- 1.59 and 17.63 +/- 1.49 in diabetic and normal rat, respectively (n = 8, P < 0.01). CONCLUSION: The results suggest that CNP induced an inhibitory effect on spontaneous contraction of gastric smooth muscle, potentiated in diabetic rat via up-regulation of the natriuretic peptides-NPR-B-particulate guanylyl cyclase-cyclic GMP signal pathway.

cAMP produced by pituitary adenylate cyclase-activating polypeptide 27 inhibits atrial natriuretic peptide secretion in rabbit beating atria.

The aim of the present study was to determine the effects of increased cAMP levels in response to pituitary adenylate cyclase-activating polypeptide 27 (PACAP27) on atrial atrial natriuretic peptide (ANP) secretion in rabbit atria. A perfused beating atrial model was used in the present study and cAMP efflux and ANP levels in atrial perfusates were measured by radioimmnoassay. At 100 nmol/L, PACAP27 increased cAMP production, which resulted in subsequent inhibition of ANP secretion. Nicardipine (1.0 micromol/L), an L-type Ca2+ channel blocker, attenuated inhibition of ANP secretion by PACAP27. Staurosporine (1.0 micromol/L), a non-specific protein kinase inhibitor, and H-89 (1.0 micromol/L), a cAMP-dependent protein kinase A (PKA) inhibitor, completely blocked the inhibition of ANP secretion in response to PACAP27 but had no effect on PACAP27-induced increases in cAMP. In conclusion, the results suggest that increased cAMP levels in response to PACAP27 negatively regulate ANP secretion via the adenylate cyclase-cAMP-PKA signalling pathway in rabbit atria and that L-type Ca2+ channels may be involved, in part, in the regulation of ANP secretion by cAMP.

Muscarinic activity modulated by C-type natriuretic peptide in gastric smooth muscles of guinea-pig stomach.

Natriuretic peptides (NPs) are a cyclic guanosine monophosphate (cGMP) generation system like nitric oxide (NO) and play an inhibitory regulation in gastrointestinal motility but the effect of NPs on muscarinic activity is still unclear. This study was designed to investigate effect of C-type natriuretic peptide (CNP) on muscarinic control of gastric motility and its ion channel mechanism. The spontaneous contraction of gastric smooth muscle strip was recorded by using physiograph in guinea-pig. Membrane currents and potential were recorded by using whole-cell patch-clamp technique. CNP significantly inhibited muscarinic M receptor agonist carbachol (Cch)-induced contractions of gastric smooth muscle strips and dramatically hyperpolarized Cch-induced depolarization of membrane potential in gastric single smooth muscle cell. Muscarinic currents induced by both Cch and GTPgammaS, a G-protein agonist were significantly suppressed by CNP. 8-Br-cGMP mimicked the effect of CNP on Cch-induced muscarinic currents, and the peak holding current was decreased from -200.66+/-54.35 pA of control to -67.35+/-24.82 pA. LY83583, a guanylate cyclase nonspecific inhibitor, significantly weakened the inhibitory effect of CNP on muscarinic current while zaprinast, a cGMP sensitive phosphoesterase inhibitor, potentiated the inhibitory effect of CNP on muscarinic current. cGMP production was dramatically enhanced by CNP and this effect was suppressed by LY83583 in gastric smooth muscle. These results suggest that CNP modulates muscarinic activity via CNP-NPR-particulate guanylate cyclase (pGC)-cGMP pathway in guinea-pig.

Effects of unsaturated fatty acids on calcium-activated potassium current in gastric myocytes of guinea pigs.

AIM: To investigate the effects of exogenous unsaturated fatty acids on calcium-activated potassium current (I(K(Ca))) in gastric antral circular myocytes of guinea pigs. METHODS: Gastric myocytes were isolated by collagenase from the antral circular layer of guinea pig stomach. The whole-cell patch clamp technique was used to record I(K(Ca)) in the isolated single smooth muscle cells with or without different concentrations of arachidonic acid (AA), linoleic acid (LA), and oleic acid (OA). RESULTS: AA at concentrations of 2,5 and 10 micromol/L markedly increased I(K(ca)) in a dose-dependent manner. LA at concentrations of 5, 10 and 20 micromol/L also enhanced I(K(Ca)) in a dose-dependent manner. The increasing potency of AA, LA, and oleic acid (OA) on I(K(Ca)) at the same concentration (10 micromol/L) was in the order of AA>LA>OA. AA (10 micromol/L)-induced increase of I(K(ca)) was not blocked by H-7 (10 micromol/L), an inhibitor of protein kinase C (PKC), or indomethacin (10 micromol/L), an inhibitor of the cyclooxygenase pathway, and 17-octadecynoic acid (10 micromol/L), an inhibitor of the cytochrome P450 pathway, but weakened by nordihydroguaiaretic acid (10 micromol/L), an inhibitor of the lipoxygenase pathway. CONCLUSION: Unsaturated fatty acids markedly increase I(K(ca)), and the enhancing potencies are related to the number of double bonds in the fatty acid chain. The lipoxygenase pathway of unsaturated fatty acid metabolism is involved in the unsaturated fatty acid-induced increase of I(K(ca)) in gastric antral circular myocytes of guinea pigs.

[Effects of purinergic analogues on spontaneous contraction and electrical activities of gastric antral circular muscle in guinea-pig].

In order to investigate the role of non-adrenergic non-cholinergic nerves in regulating mechanical and electrical activity of gastric circular smooth muscle, the effects of ATP and its analogues on gastric motility and electrical activities were observed in guinea-pig. In organ bath system, isometric force of the circular smooth muscle of guinea-pig gastric antrum was measured. Electrical activity of the muscle was recorded by using intracellular microelectrode. Electrical and mechanical activities were recorded by chart recorder. ATP and 2-MeSATP potentiated the mechanical activity but did not affect electrical activity in gastric circular smooth muscle. ATP and 2-MeSATP-induced contraction was effectively blocked by nonselective P2y-purinoceptor antagonist, reactive-blue-2 and suramin, but ATP-induced contraction was not blocked by alpha,beta-MeATP-induced desensitization of P2x-purinoceptors. However, alpha,beta-MeATP, P2x-purinoceptor agonist, attenuated slow waves with membrane hyperpolarization and inhibited contraction. The relaxation by beta,gamma-MeATP was blocked by alpha,beta-MeATP-induced desensitization of P2x-purinoceptors. ATP-induced contraction was blocked by external calcium-free, but not by nicardipine, a L-type calcium channel blocker. Indomethacin, a nonselective cyclooxygenase inhibitor, did not block ATP-induced contraction. The results suggest that: (1) ATP- and analogues-induced contraction is mediated by P2y-purinoceptor, whereas alpha,beta-MeATP-induced relaxation by P2x-purinoceptor in guinea-pig gastric antral circular smooth muscle. (2) ATP-induced contraction is dependent on extracellular calcium, but Ca2+ entry is not mediated by L-type calcium channel. (3) Prostaglandins are not involved in ATP- and analogue-induced contraction of gastric circular smooth muscle in guinea-pigs, and alpha,beta-MeATP-induced relaxation is related to membrane hyperpolarization.

Effect of actin microfilament on potassium current in guinea pig gastric myocytes.

AIM: To investigate the effect of actin microfilament on potassium current and hyposmotic membrane stretch-induced increase of potassium current in gastric antral circular myocytes of guinea pig. METHODS: Whole-cell patch clamp technique was used to record potassium current in isolated gastric myocyes. RESULTS: When the membrane potential was clamped at -60 mV, an actin microfilament disruptor, cytochanlasin-B(Cyt-B, 20 micromol/L in pipette) increased calcium-activated potassium current (I(K(Ca))) and delayed rectifier potassium current (I(K(V))) to 138.4+/-14.3% and 142.1+/-13.1% respectively at +60 mV. In the same condition, an actin microfilament stabilizer phalloidin (20 micromol/L in pipette) inhibited I(K(Ca)) and I(K(V)) to 74.2+/-7.1% and 75.4+/-9.9% respectively. At the holding potential of -60 mV, hyposmotic membrane stretch increased I(K(Ca)) and I(K(V)) by 50.6+/-9.7% and 24.9+/-3.3% at +60 mV respectively. In the presence of cytochalasin-B and phalloidin (20 micromol/L, in the pipette) condition, hyposmotic membrane stretch also increased I(K(Ca)) by 44.5+/-7.9% and 55.7+/-9.8% at +60 mV respectively. In the same condition, cytochalasin-B and phalloidin also increased I(K(V)) by 23.0+/-5.5% and 30.3+/-4.5% respectively. However, Cyt-B and phalloidin did not affect the amplitude of hyposmotic membrane stretch-induced increase of I(K(Ca)) and I(K(V)). CONCLUSION: Actin microfilaments regulate the activities of potassium channels, but they are not involved in the process of hyposmotic membrane stretch-induced increase of potassium currents in gastric antral circular myocytes of guinea pig.

Role of calcium-activated potassium currents in CNP-induced relaxation of gastric antral circular smooth muscle in guinea pigs.

AIM: To investigate ion channel mechanism in CNP-induced relaxation of gastric circular smooth muscle in guinea pigs. METHODS: Spontaneous contraction of gastric smooth muscle was recorded by a four -channel physiograph. The whole cell patch-clamp technique was used to record calcium-activated potassium currents and membrane potential in the gastric myocytes isolated by collagenase. RESULTS: C-type natriuretic peptide (CNP) markedly inhibited the spontaneous contraction in a dose-dependent manner in gastric circular smooth muscle in guinea pigs. Ly83583, an inhibitor of guanylate cyclase, weakened CNP-induced inhibition on spontaneous contraction but Zaparinast, an inhibitor of cGMP sensitive phosphoesterase, potentiated CNP-induced inhibition in gastric circular smooth muscles. The inhibitory effects of CNP on spontaneous contraction were blocked by tetrathylammonium (TEA), a nonselective potassium channel blocker. CNP hyperpolarized membrane potential from -60.0 mV+/-2.0 mV to -68.3 mV+/-3.0 mV in a single gastric myocyte. CNP increased calcium-activated potassium currents (I(K(ca))) in a dose-dependent manner in gastric circular myocytes. CNP also increased the spontaneously transient outward currents (STOCs). Ly83583 partly blocked CNP-induced increase of calcium-activated potassium currents, but Zaparinast potented the effect. CONCLUSION: CNP inhibits spontaneous contraction, and potassium channel may be involved in the process in gastric circular smooth muscle of guinea pigs. CNP-induced increase of I(K(ca)) is mediated by a cGMP dependent pathway.