| JOURNAL HOME | CME HOME | THIS MONTH | PAST ISSUES | ETOC | COLLECTIONS |
| AUTHORS | REVIEWERS | EDITORIAL BOARD | FEEDBACK | RSS | HELP |
 
|
|
|
||
|
|
Anesth Analg 2002;95:1263-1268 © 2002 International Anesthesia Research Society
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 |
Abstract |
|---|
 Top Abstract IntroductionMethodsResultsDiscussionReferences |
|---|
Using two electrode voltage clamps, we investigated the effects of lidocaine on one type of glutamate transporter, EAAT3, and the role of protein kinase C (PKC) and phosphatidylinositol 3-kinase (PI3K) in mediating the lidocaine effects. EAAT3 was expressed in Xenopus oocytes, and membrane currents were recorded after the application of L-glutamate (30 µM). Lidocaine increased glutamate-induced inward currents significantly at 2 concentrations (100 µM and 1 mM), but not at other concentrations. Lidocaine (100 µM) significantly increased the Vmax, but not the Km, of EAAT3 for glutamate compared with control. The action sites of lidocaine on EAAT3 seem to be intracellular, because only intracellularly injected QX314 (permanently charged lidocaine analog) increased the response. The combination of phorbol-12-myrisate-13-acetate, an activator of PKC, and lidocaine did not further increase the responses compared with phorbol-12-myrisate-13-acetate or lidocaine alone, although each of these three groups showed significantly bigger responses than controls. Three PKC inhibitors (staurosporine, calphostin C, and chelerythrine) did not affect the basal EAAT3 activity but abolished lidocaine-enhanced EAAT3 activity. Wortmannin (a specific PI3K inhibitor) inhibited EAAT3 basal activity and lidocaine-enhanced EAAT3 activity. Our results suggest that lidocaine enhances EAAT3 activity at certain concentrations and that PKC and PI3K may mediate these lidocaine effects.
IMPLICATIONS: By using the Xenopus oocyte expression system, we investigated the effects of lidocaine on a glutamate transporter (EAAT3). Our findings suggest that lidocaine enhances EAAT3 activity at certain concentrations and that protein kinase C and phosphatidylinositol 3-kinase may mediate these lidocaine effects.
|
Introduction |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
Local anesthetics (LAs) are widely used in clinical practice. Although LAs block sodium channels, they also affect many other ion channels (1) or intracellular signaling pathways (2,3). Thus, LAs exert diverse influences on the central nervous system. At large concentrations, they alter consciousness and ultimately lead to seizures. These neurotoxic effects of LAs may not be explained solely by their effects on sodium channels (4); the effects of LAs on excitatory (5) or inhibitory (6) neurotransmission may also contribute.
Glutamate transporters play an important role in removing extracellular glutamate in the central nervous system. Glutamate is a major excitatory amino acid neurotransmitter. Dysfunction of glutamate transporters causes extracellular glutamate accumulation, resulting in glutamate-mediated neuronal injury, which has been implicated in the pathophysiology of ischemic brain damage and other neurodegenerative disorders, such as amyotrophic lateral sclerosis (7,8). Five glutamate transporters have been characterized: excitatory amino acid transporters 1–5 (EAAT1–5). EAAT1 and EAAT2 are glial; EAAT3 and EAAT4 are neuronal; and EAAT5 is distributed in the retina. Although the physiological functions of each type of glutamate transporter are not known completely, there is some emerging evidence that dysfunction of EAAT3 can be linked to seizures. Researchers, using antisense oligonucleotides, demonstrated that animals with a decreased level of EAAT3 had epileptiform fits (9).
In this study, by using the Xenopus oocyte expression system, we investigated the effects of lidocaine, a very commonly used LA, on EAAT3 activity. We also investigated the involvement of protein kinase C (PKC) and phosphatidylinositol 3-kinase (PI3K), two important modulating kinases in intracellular signaling, in the lidocaine effects on EAAT3.
|
Methods |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
The study protocol was approved by the Institutional Animal Care and Use Committee at the University of Virginia. Isolation and microinjection of Xenopus oocytes were performed as described by Do et al. (10). The EAAT3 complementary DNA (cDNA) construct was provided by Dr. M. A. Hediger (Brigham and Women’s Hospital, Harvard Institutes of Medicine, Boston, MA). The cDNA was subcloned in a commercial vector (BluescriptSKm). The plasmid DNA was linearized with a restriction enzyme (NotI), and messenger RNA (mRNA) was synthesized in vitro with a commercially available kit (Ambion, Austin, TX). The resulting mRNA was quantified spectrophotometrically and diluted in sterile water. This mRNA was used for the cytoplasmic injection of oocytes in a concentration of 30 ng/30 nL by using an automated microinjector (Nanoject; Drummond Scientific Co., Broomall, PA). This was followed by incubation of the oocytes at 16°C for 3 or 4 days before the current recording.
Experiments were performed at room temperature (approximately 21°C–23°C). A single defolliculated oocyte was placed in a recording chamber (0.5-mL volume) and perfused with 3 mL/min of Tyrode’s solution (containing, in mM: NaCl 150, KCl 5, CaCl2 2, MgSO4 1, dextrose 10, and HEPES 10; pH was adjusted to 7.5). Microelectrodes were pulled in one stage from 10-µL capillary glass (Drummond Scientific Co.) on a micropipette puller (Model 700C; David Kopf Instruments, Tujunga, CA). Tips were broken at a diameter of approximately 10 µm. These microelectrodes had a resistance of 1–3 M
when they were filled with 3 M KCl. The oocytes were voltage-clamped by using a two-microelectrode oocyte voltage-clamp amplifier (OC725-A; Warner Corp., New Haven, CT) connected to a data acquisition and analysis system running on a personal computer. The acquisition system consisted of a DAS-8A/D conversion board (Keithley-Metrabyte, Taunton, MA), and analyses were performed with OoClamp software (11). All measurements were performed at a holding potential of -70 mV. Oocytes that did not show a stable holding current <1 µA were excluded from analysis. L-Glutamate was diluted in Tyrode’s solution and superfused over the oocyte for 20 s (3 mL/min). L-Glutamate-induced inward currents were sampled at 125 Hz for 1 min: 5 s of baseline, 20 s of agonist application, and 35 s of washing with Tyrode’s solution. Responses were quantified by integrating the current trace and reported as microcoulombs, which reflected the amount of transported glutamate. Each experiment was performed with oocytes from at least three different frogs.
Lidocaine was dissolved in distilled water and diluted in Tyrode’s solution to appropriate final concentrations (1 µM to 10 mM). In the control group, oocytes were perfused with Tyrode’s solution for 4 min before the responses were measured. In the lidocaine-treated group, oocytes were perfused with Tyrode’s solution for the first minute, followed by Tyrode’s solution with lidocaine for the next 3 min before the response measurement. To determine the effects of lidocaine on the Km and Vmax of EAAT3 for glutamate, serial concentrations of L-glutamate (3, 10, 30, 100, and 300 µM) were used. In other experiments, 30 µM L-glutamate was used to induce the glutamate transporter currents.
To delineate the action sites of lidocaine on EAAT3 activity, QX314 (a permanently charged lidocaine analog) was used. QX314 (100 µM) was applied either externally, by superfusing oocytes with the drug, or intracellularly, by injecting 50 nL of 150 mM KCl containing 100 µM QX314 into oocytes.
To study the effects of PKC activation on EAAT3 activity, oocytes were preincubated with phorbol-12-myrisate-13-acetate (PMA; 100 nM) for 10 min before recording. In addition, PMA-treated oocytes were exposed to lidocaine in the same way as described previously. To study the effects of PKC inhibitors on EAAT3 activity, oocytes were preincubated with PKC inhibitors: staurosporine (1 µM for 1 h), chelerythrine (50 µM for 1 h), or calphostin C (3 µM for 2 h). Two concentrations (1 or 10 µM) of wortmannin (a PI3K inhibitor) were incubated with oocytes (1 h) to investigate the role of PI3K in regulating EAAT3 activity.
Lidocaine and QX314 were gifts from Astra Pharmaceuticals (Westborough, MA). Molecular biology reagents were obtained from Promega (Madison, WI), and other chemicals were obtained from Sigma (St. Louis, MO) unless specified in the text.
Responses are reported as mean ± SEM. Because variability in response between batches of oocytes is common because of the different expression level of EAAT3 proteins, responses were at times normalized to the same-day controls for each batch. Differences among groups were analyzed with either Student’s t-test or analysis of variance, followed by Student-Newman-Keuls correction. P < 0.05 was considered significant.
|
Results |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
Whereas uninjected oocytes showed no response to L-glutamate (data not shown), oocytes injected with EAAT3 mRNA showed inward currents after application of L-glutamate (Fig. 1). We have shown that the response was concentration dependent and that the 50% effective concentration of EAAT3 for L-glutamate was 27.2 µM (12). Thus, 30 µM of L-glutamate was used for other studies.
|
Five concentrations of lidocaine were tested (1 µM, 10 µM, 100 µM, 1 mM, and 10 mM). Oocytes expressing EAAT3 showed significantly increased transporter current only at 100 µM and 1 mM of lidocaine (Fig. 1). Because of the bell-shaped dose-response curve, we tested a larger concentration (100 mM) to see whether significant inhibition could be achieved. However, we could not obtain reliable results because the resting currents of the oocytes became unstable 1 or 2 min after superfusion with 100 mM lidocaine. Of the two concentrations of lidocaine that enhance EAAT3 activity, 100 µM lidocaine was chosen to be used for further experiments. In addition to enhancing the responses induced by 30 µM L-glutamate, 100 µM lidocaine also significantly increased the responses induced by 100 or 300 µM L-glutamate (Fig. 2). Further analysis of the data (GraphPad Prism, Version 2.0; GraphPad, San Diego, CA) demonstrated that lidocaine significantly increased Vmax from 2.2 ± 0.2 µC for controls to 4.4 ± 0.5 µC for the lidocaine-treated group (n = 18; P < 0.05), corresponding to a twofold increase. However, lidocaine did not cause a significant change in Km (51.8 ± 14.2 µM for controls versus 73.8 ± 24.3 µM for the lidocaine group; n = 18; P > 0.05).
|
Oocytes superfused with 100 µM QX314 did not change glutamate-induced inward current compared with controls (0.7 ± 0.1 µC for the control group; 0.6 ± 0.1 µC for the QX314 group; n = 9 in each group; P > 0.05). However, QX314 administered by intracellular injection increased the response significantly (0.6 ± 0.1 µC for the control group; 0.9 ± 0.1 µC for the QX314 group; n = 12–14; P < 0.05)
Oocytes pretreated with PMA (100 nM for 10 min) showed greater EAAT3 activity than that of controls. This was in accordance with our previous study (12). To determine whether there is an interaction between the effects of PMA and lidocaine (100 µM) on EAAT3 activity, PMA (100 nM)-treated oocytes were exposed to lidocaine, and the responses were compared. Oocytes exposed to PMA, lidocaine, or both showed a significant increase in EAAT3 activity compared with control. However, there was no statistical difference among the PMA, lidocaine, or PMA plus lidocaine groups (Fig. 3). Therefore, it appears that there is no additive or synergistic interaction between PMA and lidocaine effects on EAAT3 activity, suggesting that these two agents might increase the EAAT3 activity through the same pathway.
|
Preincubation of the oocytes with staurosporine (1 µM) for 1 h did not affect EAAT3 activity compared with controls (Fig. 4). However, staurosporine abolished the lidocaine-enhanced EAAT3 activity. Similarly, two other PKC inhibitors (calphostin C at 3 µM for 2 h or chelerythrine at 50 µM for 1 h) did not inhibit the basal EAAT3 activity but abolished the lidocaine-enhanced EAAT3 activity.
|
Wortmannin at 10 µM for 1 h significantly decreased the basal and lidocaine-enhanced EAAT3 activity (Fig. 5). We then decreased the wortmannin concentration to 1 µM. Pretreatment of the oocytes with 1 µM wortmannin (1 h) also significantly decreased the basal EAAT3 activity, and the enhancement of EAAT3 activity by lidocaine was abolished by wortmannin at this smaller concentration as well (Fig. 5). In both experiments, lidocaine alone enhanced EAAT3 activity significantly by approximately 40% (37% in the 10 µM group; 46% in the 1 µM group). Although the EAAT3 activity in the combination of lidocaine and wortmannin was about 17% (19% in the 10 µM group; 14% in the 1 µM group) more than that in the presence of wortmannin alone, the activity under these two different conditions was not statistically significantly different.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
EAATs are sodium co-transporters. They transport one negatively charged glutamate molecule and two or three Na+ ions into the cell. At least one net positive charge enters the cell per glutamate transported. Thus, the transport of glutamate is electrogenic, and the size of the glutamate-induced current reflects the amount of transported glutamate. Therefore, we can measure the glutamate-induced currents to quantify EAAT activity, which has been widely used in the literature (12–14). Our results demonstrated a bell-shaped dose-response curve of lidocaine on EAAT3 activity. Concentrations (0.1 and 1 mM) in the middle of the concentration range enhanced EAAT3 activity, whereas the other tested concentrations did not have significant effects on EAAT3 activity. In addition, our kinetic study showed that 100 µM lidocaine increased the Vmax, but not the Km, of glutamate uptake, suggesting that lidocaine increases the available number or turnover rate of EAAT3 proteins in the cell membrane rather than affecting the affinity of EAAT3 to glutamate.
Lidocaine can cause seizures and was one of the most common causes of drug-induced seizures in patients in the late 1970s and early 1980s (15,16). However, lidocaine has both proconvulsant and anticonvulsant activity, depending on its blood concentration. At plasma concentrations between 0.5 and 5 µg/mL (1.8–18 µM), lidocaine suppresses partial or secondarily generalized seizures (17). At plasma concentrations from more than 8–9 µg/mL (30–33 µM), lidocaine can be a proconvulsant (18). In this study, lidocaine enhanced the activity of EAAT3 at 100 µM and 1 mM concentrations. The possible relationship between EAAT3 activity and seizure development suggests that the enhancement of EAAT3 activity by lidocaine could be a mechanism for lidocaine’s anticonvulsant effects. However, the concentrations of lidocaine to increase EAAT3 activity in this study (0.1–1 mM) are larger than those that are recognized to be anticonvulsant in the plasma (1.8–18 µM). This concentration discrepancy can be explained by two possibilities: 1) the effects of lidocaine on EAAT3 activity are not an important component for the anticonvulsant property of lidocaine, or 2) although EAAT3 is indeed involved in the anticonvulsant action of lidocaine, our experimental model created the concentration discrepancy. In this regard, some limitations should be considered when interpreting our findings with a Xenopus oocyte expression system. Xenopus oocytes are clearly different from native human cells, and our experiments were performed at room temperature (oocytes will not survive at 37°C) with rat EAAT3. These differences may have resulted in a difference in concentrations for lidocaine to achieve anticonvulsant action (found in humans) and EAAT3 activity enhancement (found in our study). In light of the biphasic effects of lidocaine on seizure development (proconvulsant and anticonvulsant activity), we attempted to use a very large concentration of lidocaine (100 mM) to test whether lidocaine also has biphasic effects on EAAT3 activity. We could not get reliable data from the oocytes exposed to 100 mM lidocaine because of the unstable conditions of the oocytes. The reason for this instability is not known; however, Kanai et al. (19) reported that exposing the rat myelinated nerve to 80 mM lidocaine for longer than 30 minutes caused membrane damage. It is conceivable that lidocaine at 100 mM might have caused membrane damage to Xenopus oocytes in this study.
To investigate the mechanisms of lidocaine enhancement of EAAT3 activity, we used QX314. QX314 is a permanently charged lidocaine analog that cannot pass through the plasma membrane. Our data demonstrated that intracellularly, but not extracellularly, applied QX314 significantly increased EAAT3 activity. These results indicate that the action sites of lidocaine on EAAT3 seem to be intracellular.
We then investigated the role of PKC and PI3K in the lidocaine effects on EAAT3. Both PKC and PI3K are intracellular signaling enzymes and have been implicated in the regulation of EAAT3 activity (12,20,21). Our results strongly suggest that PKC is involved in the lidocaine enhancement of EAAT3 activity: EAAT3 activity in the presence of lidocaine plus PMA was at a similar level as that in the presence of lidocaine or PMA alone (Fig. 3), and all three PKC inhibitors at the concentrations that did not affect the basal EAAT3 activity abolished the lidocaine-enhanced EAAT3 activity (Fig. 4). Interestingly, although PMA at 100 nM always increased the activity of rat EAAT3 expressed in oocytes in our study and in another study (12), a recent article (14) provided opposite results, also with the oocyte expression model. The reason for this discrepancy is not known. However, our results are consistent with the idea that the activation of PKC enhances EAAT3 activity, an observation supported by many studies (20,22,23).
PI3K is the key enzyme involved in the synthesis of 3-phosphoinositides, which have roles in the regulation of membrane trafficking, cell survival, maintenance of intact cytoskeleton, and PKC activity (24). The addition of some phosphoinositides has been demonstrated to activate the 
, 
, and 
isoforms of PKC. It was reported that a product of PI3K might recruit and localize substrates at the plasma membrane, thereby facilitating their phosphorylation by PKC (24). Our findings suggest that PI3K is also involved in lidocaine effects on EAAT3 activity. Although lidocaine (100 µM) increased the response significantly, by approximately 40%, in the absence of wortmannin, a PI3K inhibitor, it failed to increase the response in the presence of wortmannin.
In conclusion, our results demonstrated that lidocaine at certain concentrations enhances EAAT3 activity. The action sites of these lidocaine effects are intracellular. PKC and PI3K seem to be involved in mediating these lidocaine effects.
|
Acknowledgments |
|---|
This study was supported by departmental funds and a New Investigator Award from the Foundation for Anesthesia Education and Research/Baxter Healthcare Corporation (ZZ).
The authors thank Carl Lynch III, MD, PhD, Professor and Chair, Department of Anesthesiology, University of Virginia, for his support. We also thank Mattias A. Hediger, PhD, Associate Professor, Laboratory of Molecule and Cellular Physiology, Brigham and Women’s Hospital, for giving us the rat EAAT3 cDNA construct, and Marcel E. Durieux, MD, PhD, Professor and Chair, Department of Anesthesiology, University Hospital Maastricht, Maastricht, The Netherlands, for providing OoClamp software.
|
Footnotes |
|---|
Presented in part at the International Anesthesia Research Society Clinical and Scientific Congress, San Diego, CA, March 16–20, 2002.
|
References |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
- Butterworth JF IV, Strichartz GR. Molecular mechanisms of local anesthesia: a review. Anesthesiology 1990; 72: 711–34.[Web of Science][Medline]
- Sullivan LM, Honemann CW, Arledge JA, Durieux ME. Synergistic inhibition of lysophosphatidic acid signaling by charged and uncharged local anesthetics. Anesth Analg 1999; 88: 1117–24.
[Abstract/Free Full Text] - Hollmann MW, Fischer LG, Byford AM, Durieux ME. Local anesthetic inhibition of m1 muscarinic acetylcholine signaling. Anesthesiology 2000; 93: 497–509.[Web of Science][Medline]
- Sakura S, Bollen AW, Ciriales R, Drasner K. Local anesthetic neurotoxicity does not result from blockade of voltage-gated sodium channels. Anesth Analg 1995; 81: 338–46.[Abstract]
- McFarlane C, Warner DS, Dexter F, Todd MM. Glutamatergic antagonism: effects on lidocaine-induced seizures in the rat. Anesth Analg 1994; 79: 701–5.
[Abstract/Free Full Text] - Ikeda M, Dohi T, Tsujimoto A. Inhibition of gamma-aminobutyric acid release from synaptosomes by local anesthetics. Anesthesiology 1983; 58: 495–9.[Web of Science][Medline]
- Rothstein JD, Van Kammen M, Levey AI, et al. Selective loss of glial glutamate transporter GLT-1 in amyotrophic lateral sclerosis. Ann Neurol 1995; 38: 73–84.[Web of Science][Medline]
- Tanaka K, Watase K, Manabe T, et al. Epilepsy and exacerbation of brain injury in mice lacking the glutamate transporter GLT-1. Science 1997; 276: 1699–702.
[Abstract/Free Full Text] - Danbolt NC, Chaudhry FA, Dehnes Y, et al. Properties and localization of glutamate transporters. Prog Brain Res 1998; 116: 23–43.[Web of Science][Medline]
- Do SH, Kamatchi GL, Durieux ME. The effects of isoflurane on native and chimeric muscarinic acetylcholine receptors: the role of protein kinase C. Anesth Analg 2001; 93: 375–81.
[Abstract/Free Full Text] - Durieux ME. Ooclamp: an IBM-compatible software system for electrophysiologic receptor studies in Xenopus oocytes. Comput Methods Programs Biomed 1993; 41: 101–5.[Web of Science][Medline]
- Do SH, Kamatchi GL, Washington JM, Zuo Z. Effects of volatile anesthetics on glutamate transporter, excitatory amino acid transporter type 3: the role of protein kinase C. Anesthesiology 2002; 96: 1492–7.[Web of Science][Medline]
- Kanai Y, Hediger MA. Primary structure and functional characterization of a high-affinity glutamate transporter. Nature 1992; 360: 467–71.[Medline]
- Trotti D, Peng JB, Dunlop J, Hediger MA. Inhibition of the glutamate transporter EAAC1 expressed in Xenopus oocytes by phorbol esters. Brain Res 2001; 914: 196–203.[Web of Science][Medline]
- Pfeifer HJ, Greenblatt DJ, Koch-Weser J. Clinical use and toxicity of intravenous lidocaine: a report from the Boston collaborative drug surveillance program. Am Heart J 1976; 92: 168–73.[Web of Science][Medline]
- Messing RO, Closson RG, Simon RP. Drug-induced seizures: a 10-year experience. Neurology 1984; 34: 1582–6.
[Abstract/Free Full Text] - Lemmen LJ, Klassen M, Duiser B. Intravenous lidocaine in the treatment of convulsions. JAMA 1978; 239: 2025.
[Abstract/Free Full Text] - Garcia PA, Alldredge BK. Drug-induced seizures. Neurol Clin 1994; 12: 85–99.[Web of Science][Medline]
- Kanai Y, Katsuki H, Takasaki M. Lidocaine disrupts axonal membrane of rat sciatic nerve in vitro. Anesth Analg 2000; 91: 944–8.
[Abstract/Free Full Text] - Casado M, Bendahan A, Zafra F, et al. Phosphorylation and modulation of brain glutamate transporters by protein kinase C. J Biol Chem 1993; 268: 27313–7.
[Abstract/Free Full Text] - Sims KD, Straff DJ, Robinson MB. Platelet-derived growth factor rapidly increases activity and cell surface expression of the EAAC1 subtype of glutamate transporter through activation of phosphatidylinositol 3-kinase. J Biol Chem 2000; 275: 5228–37.
[Abstract/Free Full Text] - Dowd LA, Robinson MB. Rapid stimulation of EAAC1-mediated Na+-dependent L-glutamate transport activity in C6 glioma cells by phorbol ester. J Neurochem 1996; 67: 508–16.[Web of Science][Medline]
- Davis KE, Straff DJ, Weinstein EA, et al. Multiple signaling pathways regulate cell surface expression and activity of the excitatory amino acid carrier 1 subtype of glu transporter in C6 glioma. J Neurosci 1998; 18: 2475–85.
[Abstract/Free Full Text] - Toker A, Cantley LC. Signalling through the lipid products of phosphoinositide-3-OH kinase. Nature 1997; 387: 673–6.[Medline]
This article has been cited by other articles:
|
|
 |
|
  M. Mertl, H. Daniel, and G. Kottra Substrate-induced changes in the density of peptide transporter PEPT1 expressed in Xenopus oocytes Am J Physiol Cell Physiol, November 1, 2008; 295(5): C1332 - C1343. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. Hahnenkamp, M. E. Durieux, A. Hahnenkamp, S. K. Schauerte, C. W. Hoenemann, V. Vegh, G. Theilmeier, and M. W. Hollmann Local anaesthetics inhibit signalling of human NMDA receptors recombinantly expressed in Xenopus laevis oocytes: role of protein kinase C Br. J. Anaesth., January 1, 2006; 96(1): 77 - 87. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Z. Zuo and H. Fang Glutamate transporter type 3 attenuates the activation of N-methy-D-aspartate receptors co-expressed in Xenopus oocytes J. Exp. Biol., June 1, 2005; 208(11): 2063 - 2070. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. Hahnenkamp, M. E. Durieux, H. van Aken, S. Berning, T. J. Heyse, C. W. Honemann, and B. Linck Modulation of Xenopus laevis Ca-Activated Cl Currents by Protein Kinase C and Protein Phosphatases: Implications for Studies of Anesthetic Mechanisms Anesth. Analg., August 1, 2004; 99(2): 416 - 422. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. Thomas, W. Zhang, K. Wu, A.-B. Wimmer, B. Gut, G. Wendt-Nordahl, S. Kathofer, V. A.W. Kreye, H. A. Katus, W. Schoels, et al. Regulation of HERG potassium channel activation by protein kinase C independent of direct phosphorylation of the channel protein Cardiovasc Res, July 1, 2003; 59(1): 14 - 26. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
