Anesth Analg 1999;89:957
© 1999 International Anesthesia Research Society
NEUROSURGICAL ANESTHESIA
The Effect of Intravenous or Subarachnoid Lidocaine on Glutamate Accumulation During Transient Forebrain Ischemia in Rats
Hiromichi Terada, MD*,
Sukejuro Ohta, MD
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Toshiaki Nishikawa, MD*,
Takahide Mizunuma, MD*,
Yoichi Iwasaki, MD*, and
Yoko Masaki, PhD*
*Department of Anesthesiology, Akita University School of Medicine; and
Division of Anesthesiology, Akita Medical Center, Akita, Japan
Address correspondence and reprint requests to H. Terada, Department of Anesthesiology, Akita University School of Medicine, 1-1-1 Hondo, Akita City, Akita 010-8543, Japan. Address e-mail to hirotera{at}hi-ho.ne.jp
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Abstract
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We studied whether IV or subarachnoid (SA) lidocaine would influence the increase in extracellular glutamate concentration in the hippocampal CA1 and the cerebral cortex during transient forebrain ischemia in rats by using the dialysis electrode method. Fifty-four Sprague-Dawley rats were assigned to one of six treatment groups: IV lidocaine 5 mg/kg, IV lidocaine 10 mg/kg, IV 0.9% saline 0.5 mL/kg, SA lidocaine 5 mg/kg, SA lidocaine 10 mg/kg, and SA 0.9% saline 0.5 mL/kg (n = 9 in each group). Transient forebrain ischemia was induced by hemorrhagic hypotension and carotid artery occlusion, 15 min after administration of lidocaine or saline. The maximal values of glutamate concentration and the areas under glutamate concentration curves in the CA1 were significantly less in the IV lidocaine 10 mg/kg group than the IV saline group, whereas those in the CA1 and the cortex were significantly less in the SA lidocaine 5 and 10 mg/kg groups than the SA saline group. The accumulation of glutamate in the CA1 or the cortex during transient forebrain ischemia was attenuated by IV or SA lidocaine. We conclude that the neuroprotective effect of lidocaine against transient cerebral ischemia involves the suppression of the increase in extracellular glutamate concentration.
Implications: IV or subarachnoid lidocaine was demonstrated to suppress glutamate accumulation in the hippocampus and the cortex during transient forebrain ischemia in rats by using the dialysis electrode method. Lidocaine can have a neuroprotective effect through the suppression of the increase in extracellular glutamate concentration.
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Introduction
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Transient forebrain ischemia causes delayed neuronal death in the vulnerable regions, such as the hippocampal CA1, cortex, and striatum, 2 to 3 days after ischemia (1). Lidocaine has membrane-stabilizing effects on neurons and inhibits oxygen and glucose consumption in the brain when a large dose is administered IV (2). In several reports, the effect of IV lidocaine on neuronal damage by transient cerebral ischemia has been evaluated with cortical somatosensory evoked responses (3) and/or histopathologic observation (4–7). A small dose of lidocaine, which did not produce seizure activity in an electroencephalogram (EEG), reduced the extent of ischemic injury in the hippocampus (7).
Because the accumulation of glutamate, an excitatory neurotransmitter, during ischemia may trigger neuronal injury (8,9), there is a possibility that the neuroprotection against cerebral ischemia by lidocaine is mediated by the reduction of extracellular glutamate accumulation. There has been only one study in which the influence of lidocaine on the extracellular glutamate change in the hippocampal CA1 during the periischemic period was analyzed by a microdialysis–high-performance liquid chromatography procedure when lidocaine was administered through the microdialysis probe by replacing the perfusion fluid (6). No studies have investigated the effect of IV lidocaine or subarachnoid (SA) lidocaine, as a clue to therapeutic application, on the accumulation of extracellular glutamate during transient forebrain ischemia in rats. Moreover, the influence of lidocaine on the kinetics of extracellular glutamate in the neocortex has not been clarified.
In most studies (6,8,10,11), in vivo glutamate concentration has usually been measured by a microdialysis–high-performance liquid chromatography procedure. This conventional microdialysis method is necessary to perfuse constant perfusate and collect dialysate through the probe every few minutes and then analyze it. In contrast, a new method for measurement of in vivo extracellular glutamate concentration, the dialysis electrode method (12–14), requires neither perfusate nor dialysate, and the concentration dynamics can be analyzed continuously.
In the current experiment, we used this new method to measure changes in glutamate concentration with two dialysis electrodes stereotaxically inserted into both the hippocampal CA1 and the neocortex in a rat model of transient forebrain ischemia and evaluated the influence of IV or SA administration of lidocaine before ischemia on the extent of the extracellular glutamate accumulation.
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Methods
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The protocol of this study was approved by our institutional animal use committee. Fifty-four male Sprague-Dawley rats (310–480 g) were used. Rats were anesthetized with 3.0% isoflurane in 70% N2O and O2, tracheotomized, then ventilated with a rodent ventilator to maintain normocapnia (PaCO2 = 37.2 ± 5.4 mm Hg, mean ± SD) and normoxia (PaO2 = 130 ± 32 mm Hg) with 1% isoflurane in 70% N2O and O2 during preparation. The tail artery was cannulated to measure arterial blood pressure and to sample arterial blood. The tail venous catheter was placed to administer vecuronium IV at a rate of 1 mg/h. The right jugular vein was cannulated for withdrawal of blood to induce hypotension and ischemia. Both common carotid arteries were isolated carefully, and nylon strings were passed around the arteries. The skull was fixed to a stereotaxic apparatus, the head skin was incised, and the skull’s surface was exposed.
Rats were divided into two groups; IV (n = 27) and SA (n = 27) administration groups. For the rats of the SA administration group, a hole was drilled on the posterior end of the interparietal bone for placement of a thin catheter in the cisterna magna (15) for administration of lidocaine or 0.9% saline. A polyethylene tube, connected to a 1-mL Hamilton syringe filled with lidocaine or saline, was inserted through this hole to the cisterna magna to the depth of 6 mm and fixed by an adhesive, Alone Alpha® (Toa Gosei, Tokyo, Japan). For the rats in the IV administration group, a syringe filled with lidocaine or saline was connected via an extension tube to the jugular vein cannula.
To insert two dialysis electrodes into the hippocampal CA1 and the cortex, two holes were drilled according to the coordinates 3.8 mm caudal, 2.0 mm right from bregma and the coordinates 3.8 mm caudal, 6.0 mm left from bregma, respectively (16). The dura was incised carefully with a 26-guage needle without injuring the underlying cortex. Electrodes attached to micromanipulators were then inserted into the hippocampal CA1 and the cortex, 2.5 mm and 1.8 mm below the dura, respectively. Rectal temperature was maintained between 37.0°C and 38.0°C with a thermostatically controlled heating pad. Brain temperature was monitored with a thermal probe placed on the anterior skull surface and maintained within normothermia (37.6°C ± 0.5°C) using a heating lamp. An EEG was recorded with two electrodes inserted on the periosteum through bilateral temporal muscles and one reference electrode. Anesthesia was maintained with 0.5% isoflurane in 70% N2O and O2 until the end of the experiment. Heparin 30 IU was administered IV to prevent blood coagulation. We took an equilibration period of more than 90 min to stabilize physiologic variables. The measured values through the microdialysis electrodes at this time were taken as baseline level (zero point), and recording of the values was started from that time.
Rats in the IV and SA administration groups were further divided into three subgroups according to the administration doses of lidocaine: l% lidocaine 0.5 mL/kg (5 mg/kg), 2% lidocaine 0.5 mL/kg (10 mg/kg), and 0.9% saline 0.5 mL/kg (n = 9 in each subgroup). After the period of stabilization, lidocaine or saline was administered for 5 min through the jugular vein (in the IV administration groups) or into the cisterna magna (in the SA administration groups). Fifteen minutes later, transient forebrain ischemia was induced through bilateral carotid artery occlusion by pulling down the strings around the arteries, along with hemorrhagic hypotension of mean arterial pressure below 50 mm Hg by the withdrawal of blood from the catheter of the jugular vein (7). The start of ischemia was defined as the time when an isoelectric EEG was confirmed. At the end of 10-min ischemia, the strings around the arteries were removed, and the blood was retransfused. Reperfusion was maintained for at least 30 min. Recording of voltage derived from the electrodes was continued throughout the ischemic and reperfusion periods. In the SA lidocaine 10 mg/kg group, the measurement of glutamate concentration was performed only in the hippocampal CA1. Arterial blood gas analyses and blood glucose measurements were performed before ischemia.
After the experimental protocol, rats were killed with acute air embolization, and the brain was removed and cut into coronal sections to confirm the locations of the electrodes and the catheter used for injection of lidocaine or saline. The values of voltage recorded during the experiment were converted into the concentration values using a linear regression equation calculated from plots of glutamate concentrations against voltage recorded in vitro.
We used the microdialysis biosensor system (EES-800; Eicom, Kyoto, Japan) for continuous measurement of in vivo extracellular glutamate concentration. The dialysis electrode (model 20–10-1–1, Sycopel International, London, UK) consists of three electrodes for the detection of electric potential and inlet and outlet tubes for the perfusion of L-glutamate oxidase and is covered by the semi-permeable membrane (1 mm in length and 250 µm in diameter). The microdialysis electrode has been demonstrated to have fast time response to glutamate and linearity to glutamate concentrations (12–14). Before the experiment, dialysis electrodes were connected to electrochemical detectors (EPS-800, Eicom) and electropolymerized with O-phenylenediamine in phosphate-buffered saline bubbled with nitrogen. The electrodes were perfused with L-glutamate oxidase (Yamasa, Tokyo, Japan) at a flow rate of 0.2 µL/min throughout the measurements. Glutamate permeates into the electrode through the membrane and is oxidized by L-glutamate oxidase to produce hydrogen peroxide, which is detected on the platinum electrode. Potentials derived from the electrodes were recorded using an amplifier-AD converter into the recording and analyzing application (Chart version 3.8.8; ADInstruments, Castle Hill, NSW, Australia) on a Macintosh SE computer (Apple Computer, Inc., Cupertino, CA). Before implantation of the electrodes, dialysis electrodes were calibrated in vitro with L-glutamate (Wako-junyaku, Tokyo, Japan) solution at each concentration of 20, 40, and 60 µM. All electrodes responded to the glutamate solution in a linear fashion, and plots of the concentration versus voltage were made for later calculation.
All values are expressed as mean ± SD. Analysis of variance or Kruskal-Wallis test was used to compare the difference in physiologic data, peak values of glutamate concentration, and areas under the glutamate concentration curves among the three subgroups of each IV or SA administration group, as needed. If significant, Bonferroni posttest was performed. A P < 0.05 was considered to be statistically significant.
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Results
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Animals’ body weight, PaO2, PaCO2, pHa, base excess, blood glucose level, and rectal temperature just before the induction of ischemia were similar among groups (Table 1). The doses of SA lidocaine induced an increase in the EEG slower waves to a greater extent than IV lidocaine. Lidocaine caused neither seizure activity nor isoelectricity at any dose.
The extracellular glutamate concentration increased rapidly from the beginning of the ischemia, reached the peak level at the end of ischemia, and rapidly returned to basal level during reperfusion (Fig. 1). Peak values of glutamate concentration and areas under the glutamate concentration curves in the IV administration groups and the SA administration groups are summarized in Tables 2 and 3, respectively. Among the IV administration groups, peak values and areas under concentration curves in the hippocampal CA1, but not in the cerebral cortex, were significantly less in the lidocaine 10 mg/kg group compared with the saline group (P < 0.05). Those in the lidocaine 5 mg/kg group were similar to the saline or lidocaine 10 mg/kg group either in the hippocampal CA1 or the cerebral cortex. Among the SA administration groups, those in the lidocaine 5 mg/kg and 10 mg/kg groups were significantly less compared with the saline group (P < 0.05) in both hippocampal CA1 and the cerebral cortex. However, no difference was noted in any variables between the lidocaine 5 mg/kg and 10 mg/kg groups.
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Figure 1. Typical tracings of glutamate concentration in the hippocampal CA1 (A), and arterial blood pressure (B) of a rat in the subarachnoid lidocaine 10 mg/kg group before and during 10-min forebrain ischemia, and during reperfusion. Arterial blood pressure was maintained below 50 mm Hg by acute withdrawal of blood and the occlusion of bilateral carotid arteries. The extracellular glutamate concentration increased rapidly from the beginning of the ischemia, lasted during ischemia, reached the peak level at the end of ischemia, and rapidly returned to basal level during reperfusion. The area under glutamate concentration curve is that between the beginning and the end of ischemia (the hatched area).
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Table 2. Peak Values and Areas Under the Curves of Extracellular Glutamate Concentration in the IV Administration Groups During Transient Forebrain Ischemia Measured by the Dialysis Electrode Method
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Table 3. Peak Values and Areas Under the Curves of Extracellular Glutamate Concentration in the Subarachnoid Administration Groups During Transient Forebrain Ischemia Measured by the Dialysis Electrode Method
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Discussion
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We measured extracellular glutamate concentration continuously by dialysis electrodes and found that IV or SA administration of lidocaine attenuated the increase in glutamate concentration in the hippocampal CA1 and the cerebral cortex during ischemia.
A small dose of IV lidocaine induces slow-wave EEG activity predominantly and reduces cerebral metabolism, whereas a large dose of IV lidocaine induces seizure activity and increases cerebral metabolism (17,18). Moreover, much larger doses of IV lidocaine, which induced isoelectricity in an EEG, reduce cerebral oxygen consumption (2). Similarly, SA administration of mepivacaine in the doses that induce lower amplitude in EEG waves also decreases cerebral oxygen consumption during incomplete ischemia in dogs (19). The doses of IV lidocaine in the present experiment induced a slight increase in EEG slower waves, and SA lidocaine increased in slower waves in the EEG to a greater extent than IV lidocaine but produced neither seizure activity nor isoelectricity. Because lidocaine pretreatment in seizure-inducing doses would produce no neuroprotective effect (5,17,18), the IV or SA lidocaine 5–10 mg/kg in the present study was likely to be within the preferable doses for neuroprotection. Because lidocaine can infiltrate tissues with high affinity, SA injection via the cisterna magna may have transported lidocaine into the neocortex to a greater extent than IV injection, despite a negligible blood-brain barrier for lidocaine (20). This assumption may account for the suppression of glutamate accumulation in the neocortex during ischemia only by SA administration. Both small and large doses of SA lidocaine were effective for suppression of glutamate concentration in the hippocampal CA1, whereas only an IV large dose of lidocaine could produce the same effect, only in the hippocampal CA1 but not in the neocortex. Sutherland et al. (7) also demonstrated the reduction in the extent of ischemic injury in the hippocampus but not in the neocortex by IV lidocaine. It remains unclear why the effect of IV-administered lidocaine is more on the hippocampus than on the neocortex. Otherwise, IV lidocaine suppressed the glutamate concentration in a dose-dependent manner, but SA lidocaine did not. The reason for these differences is not clear, but one possibility is that the concentration threshold manifesting the neuroprotective effect might be different between the two vulnerable regions.
Our measurement technique for glutamate concentration, the dialysis electrode method, has many advantages over the conventional microdialysis method (12–14). This technique does not need constant infusion of perfusate through a probe or collection of dialysate, so it is unlikely to alter the microenvironment around the probe. Also, in this technique, the response time to changes in the concentration is shorter than 15 seconds, and almost continuous monitoring is possible. However, this method possesses a drawback, only one substance can be measured with one electrode, and the simultaneous measurement of two or more substances may be difficult. By using this method, we confirmed that the extracellular glutamate concentration increased rapidly from the beginning of ischemia, reached the peak level at the end of ischemia, and rapidly returned to basal level during reperfusion. This pattern of glutamate response we observed was considerably different from that derived from the conventional microdialysis method (6,8,10,11). Our pattern was similar to that reported in a four-vessel occlusion model using the electrode dialysis method by Asai et al. (14). Obrenovitch and Richards (21) reported the extracellular glutamate increase in a biphasic manner, which was composed of the first phase as a small peak lasting for less than three minutes, probably by the exocytotic release, and the second phase lasting until the end of transient ischemia. We did not recognize such a short peak in our model. In addition, we did not observe the delay in increase of extracellular glutamate after the beginning of ischemia after lidocaine administration, as reported previously (6,11). These differences may be caused mainly by the difference of responsiveness between the conventional microdialysis and the dialysis electrode method and the different induction method of ischemia.
In the present study, we did not mention the histologic protective effect of lidocaine and the relationship with the glutamate suppression. Histopathologic investigation is in progress and clinical use of lidocaine for neuroprotection requires further research.
In conclusion, the current experiment demonstrated that the pretreatment with IV or SA lidocaine attenuated the extracellular accumulation of glutamate in the hippocampal CA1 and the cortex during transient forebrain ischemia in rats. The neuroprotective effect of lidocaine against transient cerebral ischemia possibly involves the suppression of the increase in extracellular glutamate concentration.
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Acknowledgments
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The authors thank Mr. Yoshitsugu Tobe for his expert experimental assistance.
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Footnotes
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This work was attributed to and supported by the Department of Anesthesiology, Akita University School of Medicine, and supported in part by a Grant-in-Aid for Scientific Research 07457347 from the Ministry of Education, Science, and Culture, Japan.
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References
|
|---|
-
Kirino T. Delayed neuronal death in the gerbil hippocampus following ischemia. Brain Res 1982;239:57–69.[ISI][Medline]
-
Astrup J, Sørensen PM, Sørensen HR. Inhibition of cerebral oxygen and glucose consumption in the dog by hypothermia, pentobarbital, and lidocaine. Anesthesiology 1981;55:263–8.[ISI][Medline]
-
Evans DE, Kobrine AI, LeGrys DC, Bradley ME. Protective effect of lidocaine in acute cerebral ischemia induced by air embolism. J Neurosurg 1984;60:257–63.[ISI][Medline]
-
Smith ML, Auer RN, Siesjö BK. The density and distribution of ischemic brain injury in the rat following 2–10 min of forebrain ischemia. Acta Neuropathol 1984;64:319–32.[Medline]
-
Warner DS, Godersky JC, Smith ML. Failure of pre-ischemic lidocaine administration to ameliorate global ischemic brain damage in the rat. Anesthesiology 1988;68:73–8.[ISI][Medline]
-
Fujitani T, Adachi N, Miyazaki H, et al. Lidocaine protects hippocampal neurons against ischemic damage by preventing increase of extracellular excitatory amino acids: a microdialysis study in Mongolian gerbils. Neurosci Lett 1994;179:91–4.[ISI][Medline]
-
Sutherland G, Ong BY, Louw D, Sima AAF. Effect of lidocaine on forebrain ischemia in rats. Stroke 1989;20:119–22.[Abstract/Free Full Text]
-
Benveniste H, Drejer J, Schousboe A, Diemer NH. Elevation of the extracellular concentrations of glutamate and aspartate in rat hippocampus during transient cerebral ischemia monitored by intracerebral microdialysis. J Neurochem 1984;43:1369–74.[ISI][Medline]
-
Choi DW. Glutamate neurotoxicity and diseases of the nervous system. Neuron 1988;1:623–634.[ISI][Medline]
-
Kwon JY, Bacher A, Zornow MH. Riluzole does not attenuate increases in hippocampal glutamate concentrations in a rabbit model of repeated transient global cerebral ischemia. Anesth Analg 1998;86:128–33.[Abstract]
-
Patel PM, Drummond JC, Cole DJ, Goskowicz RL. Isoflurane reduces ischemia-induced glutamate release in rats subjected to forebrain ischemia. Anesthesiology 1995;82:996–1003.[ISI][Medline]
-
Albery WJ, Bontelle MG, Galley PT. The dialysis electrode: a new method for in vivo monitoring. J Chem Soc Chem Commun 1992;12:900–1.
-
Walker MC, Galley PT, Errington ML, et al. Ascorbate and glutamate release in the rat hippocampus after perforant path stimulation: a "dialysis electrode" study. Neurochem 1995;65:725–31.
-
Asai S, Iribe Y, Kohno T, Ishikawa K. Real time monitoring of biphasic glutamate release using dialysis electrode in rat acute brain ischemia. Neuroreport 1996;7:1092–6.[ISI][Medline]
-
Takemoto Y. An improved method for using cisternal cerebrospinal fluid in conscious rats for application in the measurement of catecholamines. Jpn J Physiol 1991;41:665–9.[ISI][Medline]
-
Paxinos G, Watson C. The rat brain in stereotaxic coordinates. Sydney:Academic Press, 1982.
-
Sakabe T, Maekawa T, Ishikawa T, Takeshita H. The effects of lidocaine on canine cerebral metabolism and circulation related to the electroencephalogram. Anesthesiology 1974;40:433–41.[ISI][Medline]
-
Ingvar M, Shapiro HN. Selective metabolic activation of the hippocampus during lidocaine-induced pre-seizure activity. Anesthesiology 1981;54:33–7.[ISI][Medline]
-
Ohta S. Cerebral protective, metabolic, and vascular effects of total spinal block. Masui (Jpn J Anesth) 1985;35:729–40.
-
Usubiaga JE, Moya F, Wikinski JA, et al. Relationship between the passage of local anesthetics across the blood-brain barrier and their effects on the central nervous system. Br J Anaesth 1967;39:943–7.[Abstract/Free Full Text]
-
Obrenovitch TP, Richards DA. Extracellular neurotransmitter changes in cerebral ischaemia. Cerebrovasc Brain Metab Rev 1995;7:1–54.[ISI][Medline]
Accepted for publication May 28, 1999.
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Abstract
Introduction
