Antinociceptive Effect of the Essential Oil from Croton conduplicatus Kunth (Euphorbiaceae).

Medicinal plants have been widely used in the treatment of chronic pain. In this study, we describe the antinociceptive effect of the essential oil from Croton conduplicatus (the EO 25, 50, and 100 mg/kg, i.p.), a medicinal plant native to Brazil. Antinociceptive activity was investigated by measuring the nociception induced by acetic acid, formalin, hot plate and carrageenan. A docking study was performed with the major constituents of the EO (E-caryophyllene, caryophyllene oxide, and camphor). The EO reduced nociceptive behavior at all doses tested in the acetic acid-induced nociception test (p < 0.05). The same was observed in both phases (neurogenic and inflammatory) of the formalin test. When the hot-plate test was conducted, the EO (50 mg/kg) extended the latency time after 60 min of treatment. The EO also reduced leukocyte migration at all doses, suggesting that its antinociceptive effect involves both central and peripheral mechanisms. Pretreatment with glibenclamide and atropine reversed the antinociceptive effect of the EO on the formalin test, suggesting the involvement of KATP channels and muscarinic receptors. The docking study revealed a satisfactory interaction profile between the major components of the EO and the different muscarinic receptor subtypes (M2, M3, and M4). These results corroborate the medicinal use of C. conduplicatus in folk medicine.

[Discovery of potential ATP-sensitive potassium channel openers with potential hypotensive activity from Chinese herbs based on molecular simulation].

In this research, a combined method of ligand-based pharmacophore (LBP), structure-based pharmacophore (SBP), and molecular docking was applied for virtual screening potential ATP-sensitive potassium channel (KATP) openers from Chinese herbs. LBP models were generated by 3D-QSAR pharmacophore(hypogen) program, based on the training set composed of 48 KATP agonists. The best LBP model consisted of one hydrogen-bond acceptor, one hydrogen-bond donor, one hydrophobic feature, one aromatic ring and five excluded volumes. Besides, the correlation coefficient of training set and test set, N, and CAI value of the model were 0.876 4, 0.705 8, 3.304, and 2.616 respectively. Meanwhile, SBP models were also generated based on a 3D structure of KATP (PMID: PM0079770). The best SBP model consisted of six hydrogen-bond acceptors, eight hydrogen-bond donors, seven hydrophobic features and eighteen excluded volumes. The corresponding N and CAI value were 2.200 and 2.017. Then, the best LBP model and SBP model were applied to identify potential KATP openers from Traditional Chinese Medicine Database(TCMD), respectively. 349 hits were obtained after analyzed by drug-likeness rules. Moreover, 12 compounds with high docking scores were reserved after molecular docking evaluation. Interestingly, part of the results had been verified as hypotensive active ingredients by literatures. Therefore, this study uncovers a specific target effect contained in TCMD, and provides candidates for new KATP openers' research.

Measuring and evaluating the role of ATP-sensitive K+ channels in cardiac muscle.

Since ion channels move electrical charge during their activity, they have traditionally been studied using electrophysiological approaches. This was sometimes combined with mathematical models, for example with the description of the ionic mechanisms underlying the initiation and propagation of action potentials in the squid giant axon by Hodgkin and Huxley. The methods for studying ion channels also have strong roots in protein chemistry (limited proteolysis, the use of antibodies, etc.). The advent of the molecular cloning and the identification of genes coding for specific ion channel subunits in the late 1980s introduced a multitude of new techniques with which to study ion channels and the field has been rapidly expanding ever since (e.g. antibody development against specific peptide sequences, mutagenesis, the use of gene targeting in animal models, determination of their protein structures) and new methods are still in development. This review focuses on techniques commonly employed to examine ion channel function in an electrophysiological laboratory. The focus is on the K(ATP) channel, but many of the techniques described are also used to study other ion channels.

ATP-sensitive potassium channel-mediated lactate effect on orexin neurons: implications for brain energetics during arousal.

Active neurons have a high demand for energy substrate, which is thought to be mainly supplied as lactate by astrocytes. Heavy lactate dependence of neuronal activity suggests that there may be a mechanism that detects and controls lactate levels and/or gates brain activation accordingly. Here, we demonstrate that orexin neurons can behave as such lactate sensors. Using acute brain slice preparations and patch-clamp techniques, we show that the monocarboxylate transporter blocker alpha-cyano-4-hydroxycinnamate (4-CIN) inhibits the spontaneous activity of orexin neurons despite the presence of extracellular glucose. Furthermore, fluoroacetate, a glial toxin, inhibits orexin neurons in the presence of glucose but not lactate. Thus, orexin neurons specifically use astrocyte-derived lactate. The effect of lactate on firing activity is concentration dependent, an essential characteristic of lactate sensors. Furthermore, lactate disinhibits and sensitizes these neurons for subsequent excitation. 4-CIN has no effect on the activity of some arcuate neurons, indicating that lactate dependency is not universal. Orexin neurons show an indirect concentration-dependent sensitivity to glucose below 1 mm, responding by hyperpolarization, which is mediated by ATP-sensitive potassium channels composed of Kir6.1 and SUR1 subunits. In conclusion, our study suggests that lactate is a critical energy substrate and a regulator of the orexin system. Together with the known effects of orexins in inducing arousal, food intake, and hepatic glucose production, as well as lactate release from astrocytes in response to neuronal activity, our study suggests that orexin neurons play an integral part in balancing brain activity and energy supply.