Vasorelaxing action of rutaecarpine: effects of rutaecarpine on calcium channel activities in vascular endothelial and smooth muscle cells. (33/3151)

Rutaecarpine (Rut) has been shown to induce hypotension and vasorelaxation. In vitro studies indicated that the vasorelaxant effect of Rut was largely endothelium-dependent. We previously reported that Rut increased intracellular Ca2+ concentrations ([Ca2+]i) in cultured rat endothelial cells (ECs) and decreased [Ca2+]i in cultured rat vascular smooth muscle (VSMCs) cells. The present results showed that the hypotensive effect of Rut (10-100 microgram/kg i.v.) was significantly blocked by the nitric oxide synthase inhibitor Nomega-nitro-L-arginine. In aortic rings, Rut (0. 1-3.0 microM)-induced vasorelaxation was inhibited by Nomega-nitro-L-arginine and hydroquinone but not by antagonists of the various K+ channels, 4-aminopyridine, apamin, charybdotoxin, or glibenclamide. Rut (0.1 and 1.0 microM) inhibited the norepinephrine-induced contraction generated by Ca2+ influx and at 1.0 microM increased cyclic GMP (cGMP) production in endothelium-intact rings and to a lesser extent in endothelium-denuded rings. In whole-cell patch-clamp recording, nonvoltage-dependent Ca2+ channels were recorded in ECs and Rut (0.1, 1.0 microM) elicited an opening of such channels. However, in VSMCs, Rut (10.0 microM) inhibited significantly the L-type voltage-dependent Ca2+ channels. In ECs cells, Rut (1.0, 10.0 microM) increased nitric oxide release in a Ca2+-dependent manner. Taken together, the results suggested that Rut lowered blood pressure by mainly activating the endothelial Ca2+-nitric oxide-cGMP pathway to reduce smooth muscle tone. Although the contribution seemed to be minor in nature, inhibition of contractile response in VSMCs, as evidenced by inhibition of Ca2+ currents, was also involved. Potassium channels, on the other hand, had no apparent roles.  (+info)

Increased nicotinic receptors in brains from smokers: membrane binding and autoradiography studies. (34/3151)

Chronic administration of nicotine increases the density of neuronal cholinergic nicotinic receptors in cells and in rodent brain, and similar increases have been reported in brains from human smokers. To further examine this phenomenon, we measured nicotinic receptor binding sites in brain regions from matched populations of smokers and nonsmokers. We first measured binding of [3H](+/-)epibatidine ([3H]EB) and [3H]cytisine in homogenate preparations from samples of prefrontal and temporal cerebral cortex. Binding of each radioligand was significantly higher (250-300%) in both cortical regions from brains of smokers. Frozen sections from each of the cerebral cortical regions and the hippocampus were used for autoradiographic analysis of [3H]EB binding. In cerebral cortex, binding was most dense in layer VI in the prefrontal cortex and layers IV and VI in the temporal cortex. Densitometric analysis of [3H]EB binding sites revealed marked increases of 300 to 400% of control in all cortical regions examined from smokers' brains. Binding in the hippocampal formation was heterogeneously distributed, with dense areas of binding sites seen in the parasubiculum, subiculum, and molecular layer of the dentate gyrus, and the lacunosum-moleculare layer of the CA1/2. Binding of [3H]EB was significantly higher in all six regions of the hippocampus examined from brains of smokers compared with nonsmokers. These increases ranged from 160% of control in parasubiculum to 290% in the molecular layer of the dentate gyrus. The increase in nicotinic receptors in the cerebral cortex and hippocampus of smokers may modify the central nervous system effects of nicotine and contribute to an altered response of smokers to nicotine.  (+info)

Effects of anti-rheumatic herbal medicines on cellular adhesion molecules. (35/3151)

OBJECTIVE: To test the hypothesis whether herbal medicines ameliorate inflammatory diseases via the modulation of cellular adhesion molecules (CAMs). METHODS: Human neutrophils, synovial fibroblasts, and endothelial cells were incubated with different concentrations of Tripterygium Wilfordii Hook-f (TWH-f) or Tetrandrine in the presence or absence of interleukin 1 (IL1). The amount of soluble E-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cellular adhesion molecule-1 (VCAM-1) secreted by cells were determined by ELISA. The cell surface expression of these three CAMs was detected by flow cytometry. RESULTS: TWH-f at high concentration (50 ng/ml) has a significant (p<0.05) inhibitory effect on both the secretion and the expression of the cellular adhesion molecules. However, Tetrandrine did not demonstrate the same effects. CONCLUSIONS: The cellular adhesion molecules of the endothelium and leucocytes may constitute excellent targets for the development of new anti-inflammation medicines. These results indicate that TWH could be a potential therapeutic agent in the treatment of inflammatory diseases.  (+info)

Role of protein kinase C in mitochondrial KATP channel-mediated protection against Ca2+ overload injury in rat myocardium. (36/3151)

Growing evidence exists that ATP-sensitive mitochondrial potassium channels (MitoKATP channel) are a major contributor to the cardiac protection against ischemia. Given the importance of mitochondria in the cardiac cell, we tested whether the potent and specific opener of the MitoKATP channel diazoxide attenuates the lethal injury associated with Ca2+overload. The specific aims of this study were to test whether protection by diazoxide is mediated by MitoKATP channels; whether diazoxide mimics the effects of Ca2+ preconditioning; and whether diazoxide reduces Ca2+ paradox (PD) injury via protein kinase C (PKC) signaling pathways. Langendorff-perfused rat hearts were subjected to the Ca2+ PD (10 minutes of Ca2+ depletion followed by 10 minutes of Ca2+ repletion). The effects of the MitoKATP channel and other interventions on functional, biochemical, and pathological changes in hearts subjected to Ca2+ PD were assessed. In hearts treated with 80 micromol/L diazoxide, left ventricular end-diastolic pressure and coronary flow were significantly preserved after Ca2+ PD; peak lactate dehydrogenase release was also significantly decreased, although ATP content was less depleted. The cellular structures were well preserved, including mitochondria and intercalated disks in diazoxide-treated hearts compared with nontreated Ca2+ PD hearts. The salutary effects of diazoxide on the Ca2+ PD injury were similar to those in hearts that underwent Ca2+ preconditioning or pretreatment with phorbol 12-myristate 13-acetate before Ca2+ PD. The addition of sodium 5-hydroxydecanoate, a specific MitoKATP channel inhibitor, or chelerythrine chloride, a PKC inhibitor, during diazoxide pretreatment completely abolished the beneficial effects of diazoxide on the Ca2+ PD. Blockade of Ca2+ entry during diazoxide treatment by inhibiting L-type Ca2+ channel with verapamil or nifedipine also completely reversed the beneficial effects of diazoxide on the Ca2+ PD. PKC-delta was translocated to the mitochondria, intercalated disks, and nuclei of myocytes in diazoxide-pretreated hearts, and PKC-alpha and PKC-epsilon were translocated to sarcolemma and intercalated disks, respectively. This study suggests that the effect of the MitoKATP channel is mediated by PKC-mediated signaling pathway.  (+info)

Transmembrane domain I contributes to the permeation pathway for serotonin and ions in the serotonin transporter. (37/3151)

Mutation of a conserved Asp (D98) in the rat serotonin (5HT) transporter (rSERT) to Glu (D98E) led to decreased 5HT transport capacity, diminished coupling to extracellular Na+ and Cl-, and a selective loss of antagonist potencies (cocaine, imipramine, and citalopram but not paroxetine or mazindol) with no change in 5HT Km value. D98E, which extends the acidic side chain by one carbon, affected the rank-order potency of substrate analogs for inhibition of 5HT transport, selectively increasing the potency of two analogs with shorter alkylamine side chains, gramine, and dihydroxybenzylamine. D98E also increased the efficacy of gramine relative to 5HT for inducing substrate-activated currents in Xenopus laevis oocytes, but these currents were noticeably dependent on extracellular medium acidification. I-V profiles for substrate-independent and -dependent currents indicated that the mutation selectively impacts ion permeation coupled to 5HT occupancy. The ability of the D98E mutant to modulate selective aspects of substrate recognition, to perturb ion dependence as well as modify substrate-induced currents, suggests that transmembrane domain I plays a critical role in defining the permeation pathway of biogenic amine transporters.  (+info)

Effects of huperzine A on nucleus basalis magnocellularis lesion-induced spatial working memory deficit. (38/3151)

AIM: To study the effects of huperzine A on nucleus basalis magnocellularis (NBM) lesion-induced spatial working memory impairment. METHODS: A delayed-non-match-to-sample radial arm maze task was used to study spatial working memory. The choline acetyltransferase (ChAT) activity was determined by the conversion of [3H]acetyl-CoA to [3H]ACh. RESULTS: Unilateral NBM lesion by kainic acid 0.02 mumol impaired rat's ability to perform this working memory task as evidenced by fewer correct choices after different delay intervals and more total errors to complete the task. This behavioral impairment associated with a decrease in the activity of ChAT by about 40% in the ipsilateral cerebral cortex. Huperzine A (0.2 mg.kg-1 i.p. 30 min before testing) ameliorated this spatial working memory impairment. Physostigmine (0.2-0.3 mg.kg-1 i.p. 20 min before testing) also attenuated the NBM lesion-induced memory deficit. CONCLUSION: The integrity of NBM is critical for spatial working memory processing, and this working memory impairment induced by NBM lesion can be ameliorated by huperzine A and physostigmine.  (+info)

Effects of N-methyl berbamine on delayed outward potassium current in isolated rat hepatocytes. (39/3151)

AIM: To study the effects of N-methyl berbamine (NMB) on the delayed outward potassium currents (Ik) in isolated rat hepatocytes. METHODS: With patch-clamp techniques and whole-cell recording method, holding potential -50 mV, command potential +30 to +140 mV, duration 900 ms. RESULTS: NMB reduced Ik in a concentration-dependent manner. When the concentrations of NMB were 20, 50, 400 nmol.L-1 and 50 mumol.L-1, the amplitude values of Ik were decreased to 3.6 +/- 0.4 (P > 0.05), 2.1 +/- 1.6 (P > 0.05), 3.7 +/- 1.6 (P < 0.05), 2.3 +/- 1.3 nA (P < 0.01) from 4.4 +/- 1.0 (n = 4), 2.5 +/- 1.8 (n = 4), 5.8 +/- 2.1 (n = 5), 4.6 +/- 1.3 (n = 6) nA of control, respectively. The inhibitory rates were 10%, 15%, 37%, and 51%, respectively. CONCLUSION: NMB was a K+ channel inhibitor.  (+info)

Anticholinesterase effects of huperzine A, E2020, and tacrine in rats. (40/3151)

AIM: To compare the anticholinesterase effects of huperzine A (Hup A), E2020, and tacrine in rats. METHODS: Spectrophotometry was used to determine AChE activity in brain and BuChE activity in serum. RESULTS: Following intragastric gavage, Hup A, E2020, and tacrine all produced dose-dependent inhibitions of brain AChE. Oral Hup A exhibited a higher inhibition than E2020 and tacrine. Tacrine was more effective in inhibiting serum BuChE correlated with severe peripheral adverse effects. The BuChE activity was less affected by Hup A and E2020. After a single oral dose of Hup A, a relatively steady state of AChE inhibition produced, which was longer than that after E2020 and tacrine. No change in the cholinesterase inhibition was seen for the 3 drugs following repeated i.g. medications. CONCLUSION: Hup A i.g. exhibited a higher efficacy, a longer duration of action, and a more selective inhibition on AChE than E2020 and tacrine.  (+info)