Anesthetic choice of halothane versus propofol: impact on experimental perioperative stroke.

BACKGROUND AND PURPOSE: It is not known whether preischemic exposure to anesthetic agents affects the amount of damage from transient focal ischemia that occurs after cessation of the anesthetic. We compared the effect of prior exposure to halothane or propofol on infarction size after transient middle cerebral artery occlusion (MCAO) induced in the awakening animal to test the hypothesis that anesthetic type and exposure duration would independently affect the amount of brain injury. METHODS: Male Wistar rats (weight, 200 to 300 g) were anesthetized briefly with halothane for placement of hemodynamic instrumentation. Twenty-four hours later, rats were treated with either a short (approximately 1 hour) or long (8 hours) duration of inhaled halothane (1% to 2%) or intravenous propofol (10 mg/kg bolus, 30 mg/kg per hour infusion). Each cohort (n=8 per group) was then subjected to 2-hour MCAO by the intraluminal suture technique. All anesthesia was discontinued once MCAO was achieved. Infarct volume was measured at 22 hours of reperfusion. In a second cohort, regional cerebral blood flow (CBF) was measured ([(14)C]iodoantipyrine autoradiography) at end-occlusion in short-duration halothane (n=5) or short-duration propofol (n=5) anesthesia groups and in corresponding surgical shams (n=3 each). RESULTS: Pericranial temperature, PaO(2), PaCO(2), and blood pressure were controlled and not different among groups before or during occlusion. MCAO resulted in a similar immediate reduction in laser-Doppler flow signal after discontinuation of anesthesia in the awakening animals. Infarct volume was smaller in rats exposed to short-duration halothane in cortex (87.5+/-16.6 mm(3)) (mean+/-SEM) and caudoputamen (38.3+/-13.7 mm(3)) compared with rats exposed to short-duration propofol (cortex, 177.5+/-16.9 mm(3); caudoputamen, 47.8+/-2.9 mm(3)). Infarct volume was not different in long-duration halothane versus long-duration propofol treatment. Absolute cortical or caudoputamen intraischemic CBF was not different between short-duration halothane or short-duration propofol treatment. CONCLUSIONS: These data demonstrate that short-duration halothane exposure before MCAO in the awakening animal attenuates infarction volume compared with propofol. This protection by halothane is not mediated through preservation of intraischemic CBF. Longer durations of halothane exposure may activate secondary injury pathways, which negate the protective effects of short-term halothane preischemic treatment.

Neuroprotective effect of sigma(1)-receptor ligand 4-phenyl-1-(4-phenylbutyl) piperidine (PPBP) is linked to reduced neuronal nitric oxide production.

BACKGROUND AND PURPOSE: The potent final sigma(1)-receptor ligand 4-phenyl-1-(4-phenylbutyl) piperidine (PPBP) provides neuroprotection in experimental stroke. We tested the hypothesis that PPBP attenuates striatal tissue damage after middle cerebral artery occlusion (MCAO) by a mechanism involving reduction of ischemia-evoked nitric oxide (NO) production. Furthermore, we determined whether the agent fails to protect ischemic brain when neuronal nitric oxide synthase (nNOS) is genetically deleted or pharmacologically inhibited (selective nNOS inhibitor, 7-nitroindazole [7-NI]). METHODS: Halothane-anesthetized adult male Wistar rats were subjected to 2 hours of MCAO by the intraluminal filament occlusion technique. All physiological variables were controlled during the ischemic insult. In vivo striatal NO production was estimated via microdialysis by quantification of local, labeled citrulline recovery after labeled arginine infusion. In a second series of experiments, nNOS null mutants (nNOSKOs) and the genetically matched wild-type (WT) strain were treated with 90 minutes of MCAO. Brains were harvested at 22 hours of reperfusion for measurement of infarction volume by triphenyltetrazolium chloride histology. RESULTS: PPBP attenuated infarction volume at 22 hours of reperfusion in cerebral cortex and striatum and markedly attenuated NO production in ischemic and nonischemic striatum during occlusion and early reperfusion. Treatment with 7-NI mimicked the effects of PPBP. In WT mice, infarction volume was robustly decreased by both PPBP and 7-NI, but the efficacy of PPBP was not altered by pharmacological nNOS inhibition in combined therapy. In contrast, PPBP did not decrease infarction volume in nNOSKO mice. CONCLUSIONS: These data suggest that the mechanism of neuroprotection of PPBP in vivo is through attenuation of nNOS activity and ischemia-evoked NO production. Neuroprotective effects of PPBP are lost when nNOS is not present or is inhibited; therefore, PPBP likely acts upstream from NO generation and its subsequent neurotoxicity.

Administration of selective endothelin receptor type A antagonist Ro 61-1790 does not improve outcome in focal cerebral ischemia in cat.

The authors examined the effect of selective endothelin (ET) receptor type A (ET(A)) antagonism on histological and functional recovery in cat at 24 hours after reversible middle cerebral artery occlusion (MCAO). A novel and specific ET(A) antagonist, Ro 61-1790 [5-methylpyridine-2-sulfonic acid-6-(2-hydroxyethoxy)-5-(2-methoxyphenoxy)-2-(2-1H-tetrazol-5-y l-pyridin-4-yl)-pyrimidin-4-ylamide sodium salt (1:2)] (Roche, Basel, Switzerland), was used at doses that produced steady-state plasma concentrations and abolished ET-induced pial arteriolar vasoconstriction. In a cranial window preparation, 8 nmol/L ET constricted pial arterioles by 33 +/- 18% (mean +/- SD), but this response was ablated by intravenous Ro 61-1790 treatment (10-mg/kg bolus, 4-mg/kg/h infusion). In additional animal cohorts, halothane-anesthetized cats were treated with 90 minutes of MCAO and 24 hours of reperfusion. Animals received Ro 61-1790 infusion beginning at the onset of reperfusion and continuing for 6 or 24 hours (n = 41). Control cats were treated with 0.9% saline by intravenous infusion throughout reperfusion. There was no difference in injury volume or neurologic evaluation score in saline-treated cats (n = 11; caudate 24 +/- 28%, cortical injury 7.5 +/- 5% of ipsilateral structure; score 52 +/- 8) versus the results in cats treated with Ro 61-1790 for either 24 hours (n = 6; caudate 22 +/- 23%, cortex 6 +/- 5%, injury volume of ipsilateral structure; score 55 +/- 3) or 6 hours (n = 11; caudate 33 +/- 30%, cortex 12 +/- 14%, injury volume of ipsilateral structure; score 50 +/- 10). Mortality was greatest in the 24-hour drug treatment group. These data suggest that blockade of ET(A) receptor activity is not beneficial to tissue or functional outcomes from experimental stroke in cat.

Oxotremorine-induced cerebral hyperemia does not predict infarction volume in spontaneously hypertensive or stroke-prone rats.

OBJECTIVES: We tested the following hypotheses: a) spontaneously hypertensive stroke-prone rats (SHR-SP) have more brain injury than spontaneously hypertensive rats (SHR) and normotensive controls (Wistar-Kyoto rats [WKY]) when exposed to transient focal ischemia; b) infarction size is not correlated with baseline blood pressure; and c) infarction size is inversely related to the cerebral hyperemic response to oxotremorine, a muscarinic agonist that increases cerebral blood flow (CBF) by stimulating endothelial nitric oxide synthase. DESIGN: In vivo study. SETTING: Animal laboratory in a university teaching hospital. SUBJECTS: Adult age-matched male WKY, SHR, and SHR-SP. INTERVENTIONS: Rats were instrumented under halothane anesthesia. Transient focal cerebral ischemia was produced for 2 hrs with the intravascular suture technique. Cerebral perfusion, estimated with laser Doppler flowmetry (LD-CBF), in response to intravenous oxotremorine, was measured in one cohort of rats to estimate endothelial nitric oxide synthase function. Infarction volume was measured at 22 hrs of reperfusion with 2,3,5-triphenyltetrazolium chloride staining. MEASUREMENTS AND MAIN RESULTS: Infarction volume in the striatum of SHR-SP (42+/-4 mm3) was greater than in SHR (29+/-6 mm3) or WKY (1+/-1 mm3) (n = 9 rats/strain). Resting (unanesthetized) mean arterial blood pressure was similar in SHR-SP (177+/-5 mm Hg) and SHR (170+/-5 mm Hg) despite a greater infarction volume in SHR-SP (n = 4) compared with SHR (n = 5). The percentage increase in LD-CBF signal in response to oxotremorine was similar for both groups (SHR, 64%+/-22% [n = 10]; SHR-SP, 69%+/-22% [n = 8]). However, in this cohort, cortical infarction volume was less in SHR (30%+/-4% of ipsilateral cortex) than in SHR-SP (49%+/-2% of ipsilateral cortex). CONCLUSIONS: Although SHR-SP have greater infarction volume than SHR, the mechanism of injury does not appear to be related to a difference in unanesthetized baseline mean arterial blood pressure or to an alteration in endothelium-produced nitric oxide.

Antioxidant LY231617 enhances electrophysiologic recovery after global cerebral ischemia in dogs.

OBJECTIVE: The potent antioxidant LY231617 (2,6-bis(1,1-dimethylethyl)-4-[[(1-ethyl)amino]methyl]phenol hydrochloride) is cytoprotective in models of focal and global cerebral ischemia. We tested the hypothesis that administration of LY231617, before the insult, would improve recovery of cerebral electrical activity and metabolic function after transient global cerebral ischemia by improving cerebral blood flow (CBF) during the reperfusion period. DESIGN: Randomized, controlled, prospective study. SETTING: Research laboratory at a university teaching hospital. SUBJECTS: Twenty-four male beagle dogs. INTERVENTIONS: All experiments were performed under pentobarbital anesthesia and controlled conditions of normoxia, normocarbia, and normothermia. Twelve control dogs received 20 mL/kg saline (vehicle) bolus into the right atrium and 0.01 mL/kg/min i.v., beginning 20 mins before 13 mins of global cerebral ischemia (by aortic occlusion). The dogs in the drug-treated group received LY231617 as a 10-mg/kg bolus 20 mins before ischemia and 5 mg/kg/hr throughout reperfusion (n = 12). CBF was measured using radiolabeled microspheres. MEASUREMENTS AND MAIN RESULTS: Total CBF, cerebral oxygen consumption, and somatosensory evoked potentials (SEP) were measured during 240 mins of reperfusion. CBF was similar in both vehicle- and LY231617-treated animals at baseline and throughout the experimental period. In all animals, SEP became isoelectric between 60 and 100 secs after cross-clamping of the ascending aorta. SEP amplitude recovery was significantly higher in drug-treated animals compared with controls (73%+/-15% vs. 39%+/-14% [mean+/-SEM] from baseline at 120 mins [p<.05] and 86%+/-12% vs. 49%+/-14% from baseline at 240 mins [p< .05]). CONCLUSIONS: LY231617 improves recovery of cerebral electrical function after complete transient global ischemia via mechanisms unrelated to cerebral circulatory effects.

sigma(1)-receptor ligand 4-phenyl-1-(4-phenylbutyl)-piperidine affords neuroprotection from focal ischemia with prolonged reperfusion.

BACKGROUND AND PURPOSE: We previously showed that the intravenous administration of the potent final sigma(1)-receptor ligand 4-phenyl-1-(4-phenylbutyl)-piperidine (PPBP) provides neuroprotection against transient focal cerebral ischemia and that the protection depends on treatment duration. We tested the hypothesis that PPBP would provide neuroprotection in a model of transient focal ischemia and 7 days of reperfusion in the rat as assessed with neurobehavioral outcome and infarction volume. METHODS: Under the controlled conditions of normoxia, normocarbia, and normothermia, halothane-anesthetized male Wistar rats were subjected to 2 hours of middle cerebral artery occlusion (MCAO) with the intraluminal suture occlusion technique. We used laser Doppler flowmetry to assess MCAO. At 60 minutes after the onset of ischemia, rats were randomly assigned to 1 of 4 treatment groups in a blinded fashion and received a continuous intravenous infusion of control saline or 0.1, 1, or 10 micromol. kg(-1). h(-1) PPBP for 24 hours. Neurobehavioral evaluation was performed at baseline (3 to 4 days before MCAO) and at 3 and 7 days of reperfusion. Infarction volume was assessed with triphenyltetrazolium chloride staining on day 7 of reperfusion in all rats. RESULTS: Triphenyltetrazolium chloride-determined infarction volume of ipsilateral cortex was smaller in rats treated with 10 micromol. kg(-1). h(-1) PPBP (n=15, 68+/-12 mm(3), 18+/-3% of contralateral structure, P<0.05) (mean+/-SEM) compared with corresponding rats treated with saline (n=15, 114+/-11 mm(3), 31+/-3% of contralateral structure). PPBP did not provide significant neuroprotection in the caudoputamen complex. Although MCAO was associated with several alterations in behavior, the treatment with PPBP had no effect on behavioral outcomes. CONCLUSIONS: The data demonstrate that the potent final sigma(1)-receptor ligand PPBP decreases cortical infarction volume without altering neurobehavior after transient focal ischemia and prolonged reperfusion in the rat.

Effect of AR-R 17477, a potent neuronal nitric oxide synthase inhibitor, on infarction volume resulting from permanent focal ischemia in rats.

OBJECTIVE: We tested whether AR-R 17477, a selective inhibitor of neuronal nitric oxide synthase, reduces brain injury in rats subjected to permanent focal ischemia. DESIGN: Randomized within cohort; nonblinded study. SETTING: University basic science laboratory. SUBJECTS: Halothane-anesthetized male Wistar rats (n = 53). INTERVENTIONS: Rats were treated with either intravenous saline (diluent) or AR-R 17477 (1 or 3 mg/kg) 30 mins before or 60 mins after the onset of permanent focal cerebral ischemia. Infarction volume was determined at 18 or 48 hrs of ischemia. MEASUREMENTS AND MAIN RESULTS: Pretreatment with 1 mg/kg AR-R 17477 was associated with a decreased infarct volume (2,3,5-triphenyltetrazolium chloride staining) in the striatum (saline, 81+/-7 mm3; AR-R 17477, 55+/-3 mm3) but not in the cortex at 18 hrs of occlusion (saline, 302+/-29 mm3; AR-R 17477, 237+/-36 mm3). However, this therapeutic effect of AR-R 17477 was no longer evident if the rats were allowed to survive for 48 hrs before analysis of infarction volume. In fact, in this separate cohort of animals, three of eight AR-R 17477-treated and five of eight saline-treated rats died before completing 48 hrs of ischemia. Efficacy of AR-R 17477 was completely absent (even at 18 hrs of ischemia) when drug treatment was delayed until 1 hr after the onset of ischemia. Infarction volume at 18 hrs of ischemia was similar between rats treated with saline, 1 mg/kg (cortex, 229+/-43 mm3; striatum, 67+/-8 mm3) or 3 mg/kg AR-R 17477 (cortex, 284+/-34 mm3; striatum, 75+/-5 mm3). In addition, only one of eight rats treated with 3 mg/kg AR-R 17477 at 1 hr of ischemia survived 48 hrs of occlusion, compared with three of eight rats treated with saline. CONCLUSIONS: Neuronally generated nitric oxide is a mediator of brain injury during permanent focal ischemia in rats. However, severity of the ischemic insult appears to limit the therapeutic efficacy of the specific neuronal nitric oxide synthase inhibitor, AR-R 17477.

Neuroprotection from focal ischemia by 4-phenyl-1-(4-phenylbutyl) piperidine (PPBP) is dependent on treatment duration in rats.

UNLABELLED: The IV administration of the potent sigma1-receptor ligand 4-phenyl-1-(4-phenylbutyl)piperidine (PPBP) provides neuroprotection against focal cerebral ischemia. We tested the hypothesis that prolonged, continuous administration of PPBP would provide further neuroprotection in a rat model of transient focal ischemia and reperfusion. Under controlled conditions of normoxia, normocarbia, and normothermia, halothane-anesthetized male Wistar rats were subjected to 2 h of middle cerebral artery occlusion by the intraluminal occlusion technique. Sixty minutes after the onset of ischemia, rats were randomly assigned to six treatment groups to receive a continuous IV infusion of PPBP (1 micromol . kg(-1). h(-1) for 1, 2, 3, or 4 days or saline for 1 or 4 days. The infarction volume was assessed by triphenyltetrazolium chloride (TFC) staining on Day 4 after ischemia in all rats. The TTC-determined infarction volume of the ipsilateral cerebral cortex was smaller in rats treated with PPBP for 1 day (42+/-13 mm3; 10%+/-3% of ipsilateral hemisphere; P < 0.05) (mean+/-SEM) compared with that in corresponding 1-day control rats (124+/-22 mm; 29%+/-5% of ipsilateral hemisphere; P < 0.05) or 4-day control rats (112+/-10 mm; 26%+/-2% of ipsilateral hemisphere; P < 0.05). Cortical infarction volumes in 2-, 3-, and 4-day PPBP-treated rats were not different compared with 1- and 4-day saline-treated controls. These data demonstrate that the sigma1(-receptor ligand PPBP attenuates ischemic injury when administration is initiated 60 min after the onset of focal ischemia but that prolonged continuous treatment with PPBP beyond 24 h provides no neuroprotection. IMPLICATIONS: sigma-Ligands decrease infarction size in various animal models when given after the onset of stroke. Prolonged treatment with a potent sigma-ligand is associated with loss of therapeutic efficacy for this compound.

Potent sigma1-receptor ligand 4-phenyl-1-(4-phenylbutyl) piperidine modulates basal and N-methyl-D-aspartate-evoked nitric oxide production in vivo.

BACKGROUND AND PURPOSE: final sigma-Receptor ligands ameliorate ischemic neuronal injury and modulate neuronal responses to N-methyl-D-aspartate (NMDA) receptor stimulation. Because NMDA-evoked synthesis of nitric oxide (NO) may play an important role in excitotoxic-mediated injury, we tested the hypothesis that final sigma-receptor ligands attenuate basal and NMDA-evoked NO production in the striatum in vivo. METHODS: Microdialysis probes were placed bilaterally into the striatum of halothane-anesthetized adult Wistar rats. Rats were divided into 7 treatment groups and perfused with artificial cerebrospinal fluid (aCSF) containing 3 micromol/L [14C]L-arginine for 2 to 3 hours followed by NMDA in various combinations with the following drugs: L-nitroarginine (L-NNA); the final sigma1-receptor ligand 4-phenyl-1-(4-phenylbutyl) piperidine (PPBP); the selective final sigma1-receptor antagonist 1-(cyclopropylmethyl)-4-(2'-oxoethyl) piperidine hydrobromide (DuP 734); and the noncompetitive NMDA receptor blocker MK-801 in aCSF. Right-left differences between [14C]L-citrulline in the effluent from rats treated with different drug combinations were assumed to reflect differences in NO production. RESULTS: After a 3-hour loading period with [14C]L-arginine, addition of 1 mmol/L NMDA increased [14C]L-citrulline recovery compared with aCSF alone. This NMDA-evoked increase was inhibited by 1 mmol/L of L-NNA and PPBP. Perfusion of 1 mmol/L of the final sigma1-receptor antagonist DuP 734 with 1 mmol/L PPBP augmented NMDA-evoked [14C]L-citrulline recovery compared with perfusion with PPBP and NMDA. MK-801 attenuated the basal as well as NMDA-evoked [14C]L-citrulline recovery. PPBP did not cause any further attenuation in the basal and NMDA-evoked [14C]L-citrulline recovery in the presence of MK-801. CONCLUSIONS: These data indicate that a final sigma1-receptor ligand attenuates basal as well as NMDA-evoked NO production. Because the attenuated NO production was reversed by DuP 734, PPBP appears to act as an agonist at the final sigma1-receptor. Attenuated NO production by final sigma1-receptor agonists provides one possible mechanism for focal ischemic neuroprotection.

The effect of the prone position on pulmonary mechanics is frame-dependent.

UNLABELLED: By compressing the abdomen and restricting chest wall movement, the prone position compromises pulmonary compliance. For spine surgery, placing the anesthetized patient into the prone position increases the risk of improper ventilation. In this study, we tested the hypothesis that the compromise in pulmonary compliance is related to the patient's body habitus and the surgical frame used to support the patient while in the prone position. Seventy-seven adult patients were divided into three groups according to body mass index: normal (n = 36) < or = 27 kg/m2, heavy (n = 21) 28-31 kg/m2, and obese (n = 20) > or = 32 kg/m2. Patients were placed in the prone position supported by chest rolls, a Wilson frame, or the Jackson spinal surgery table (Jackson table) according to the surgeon's preferences. Peak airway pressure (at the proximal endotracheal tube), pleural pressure (esophageal balloon), and mean arterial pressure were recorded in the supine position and prone position within 15 min of the turn. Dynamic mean (+/- SD) pulmonary compliance (mL/cm H2O) decreased when turning from the supine to the prone position in all three body mass groups when using chest rolls (normal 37+/-5 to 29+/-6; heavy 43+/-2 to 34+/-4; obese 42+/-8 to 32+/-6) or the Wilson frame (normal 39+/-6 to 32+/-7; heavy 43+/-16 to 34+/-10; obese 36+/-11 to 28+/-9). The dynamic pulmonary compliance was not altered in patients positioned on the Jackson table. Regardless of body habitus, using the Jackson table for prone positioning was not associated with a significant alteration in pulmonary or hemodynamic variables. We conclude that moving patients from the supine to the prone position during anesthesia results in a decrease in pulmonary compliance that is frame-dependent but that is not affected by body habitus. IMPLICATIONS: We hypothesized that compromise in pulmonary compliance in the prone position is related to the patient's body mass index and the surgical frame used. In this study, we demonstrated that prone positioning during anesthesia results in a decrease in pulmonary compliance that is frame-dependent but that is not affected by body mass index.

Intravenous basic fibroblast growth factor does not ameliorate brain injury resulting from transient focal ischemia in cats.

This study sought to test the hypothesis that intravenous basic fibroblast growth factor (bFGF) inhibits the development of brain injury during transient focal ischemia. Halothane-anesthetized cats (n=39) underwent left middle cerebral artery occlusion for 60 minutes. After the onset of reperfusion, wounds were closed and the cats were allowed to emerge from anesthesia. Experimental cats were treated with intravenous bFGF at a dose of either 2 or 5 microg/kg per hour, beginning 45 minutes after initiation of ischemia and continuing until 24 hours of reperfusion, when neurologic function and infarction volume were evaluated. The cats in the control group received diluent. Three of thirteen cats treated with bFGF 2 microg/kg/hour and six of sixteen cats treated with bFGF 5 microg/kg/hour died during the 24 hour reperfusion period. There was no difference in injury volume or neurologic evaluation score in the control group (n=10; hemisphere injury, 1301+/-306 mm3, mean+/-SE; score 53+/-3), and cats treated with either 2 microg/kg/hour (n=10; hemisphere injury, 1170+/-292 mm3; score 50+/-3) or 5 microg/kg/hour bFGF (n=10; hemisphere injury, 1343+/-374 mm3; score 50+/-2). The data collected do not support the hypothesis that intravenous bFGF is neuroprotective in a cat model of transient focal ischemia.

Neurodegeneration in excitotoxicity, global cerebral ischemia, and target deprivation: A perspective on the contributions of apoptosis and necrosis.

In the human brain and spinal cord, neurons degenerate after acute insults (e.g., stroke, cardiac arrest, trauma) and during progressive, adult-onset diseases [e.g., amyotrophic lateral sclerosis, Alzheimer's disease]. Glutamate receptor-mediated excitotoxicity has been implicated in all of these neurological conditions. Nevertheless, effective approaches to prevent or limit neuronal damage in these disorders remain elusive, primarily because of an incomplete understanding of the mechanisms of neuronal death in in vivo settings. Therefore, animal models of neurodegeneration are crucial for improving our understanding of the mechanisms of neuronal death. In this review, we evaluate experimental data on the general characteristics of cell death and, in particular, neuronal death in the central nervous system (CNS) following injury. We focus on the ongoing controversy of the contributions of apoptosis and necrosis in neurodegeneration and summarize new data from this laboratory on the classification of neuronal death using a variety of animal models of neurodegeneration in the immature or adult brain following excitotoxic injury, global cerebral ischemia, and axotomy/target deprivation. In these different models of brain injury, we determined whether the process of neuronal death has uniformly similar morphological characteristics or whether the features of neurodegeneration induced by different insults are distinct. We classified neurodegeneration in each of these models with respect to whether it resembles apoptosis, necrosis, or an intermediate form of cell death falling along an apoptosis-necrosis continuum. We found that N-methyl-D-aspartate (NMDA) receptor- and non-NMDA receptor-mediated excitotoxic injury results in neurodegeneration along an apoptosis-necrosis continuum, in which neuronal death (appearing as apoptotic, necrotic, or intermediate between the two extremes) is influenced by the degree of brain maturity and the subtype of glutamate receptor that is stimulated. Global cerebral ischemia produces neuronal death that has commonalities with excitotoxicity and target deprivation. Degeneration of selectively vulnerable populations of neurons after ischemia is morphologically nonapoptotic and is indistinguishable from NMDA receptor-mediated excitotoxic death of mature neurons. However, prominent apoptotic cell death occurs following global ischemia in neuronal groups that are interconnected with selectively vulnerable populations of neurons and also in nonneuronal cells. This apoptotic neuronal death is similar to some forms of retrograde neuronal apoptosis that occur following target deprivation. We conclude that cell death in the CNS following injury can coexist as apoptosis, necrosis, and hybrid forms along an apoptosis-necrosis continuum. These different forms of cell death have varying contributions to the neuropathology resulting from excitotoxicity, cerebral ischemia, and target deprivation/axotomy. Degeneration of different populations of cells (neurons and nonneuronal cells) may be mediated by distinct or common causal mechanisms that can temporally overlap and perhaps differ mechanistically in the rate of progression of cell death.

The effect of needle gauge and lidocaine pH on pain during intradermal injection.

UNLABELLED: Local anesthetics can produce pain during skin infiltration. We designed a randomized, prospective trial to determine whether needle gauge and/or solution pH affect pain during the intradermal infiltration of lidocaine. After approval by our institution's human studies review board, 40 healthy adult volunteers gave their consent to participate in this study. All of the volunteers randomly received four intradermal injections. Each volunteer was blinded as to the content of the intradermal injections and to which needle size was used for each injection. Each volunteer randomly received a 0.25-mL intradermal injection of the following four solutions: 1) lidocaine 2% administered through a 25-gauge needle (lido-25); 2) lidocaine 2% mixed with sodium bicarbonate (4 mL of 2% lidocaine plus 1 mL of sodium bicarbonate, pH 7.26) administered through a 25-gauge needle (lido-bicarb-25); 3) lidocaine 2% administered through a 30-gauge needle (lido-30); and 4) lidocaine 2% mixed with sodium bicarbonate (4 mL of 2% lidocaine plus 1 mL of sodium bicarbonate) administered through a 30-gauge needle (lido-bicarb-30). In each patient, the injection site was in the same region for each of the four injections. The skin wheal was tested for appropriate anesthesia using a 19-gauge needle on the skin wheal. A visual analog pain score was recorded after each intradermal injection. The pain scores were significantly higher in the lido-25 (3.2 +/- 0.2) group than in the lido-30 (2.5 +/- 0.3), lido-bicarb-25 (1.9 +/- 0.2), and lido-bicarb-30 (1.3 +/- 0.2) groups. The lido-bicarb-30 injection was also rated as less painful than the lido-30 injection. We found no differences between the lidobicarb-25 and the lido-bicarb-30 injections. Complete analgesia for the 19-gauge needle pain stimulus was achieved in all patients for each injection. We conclude that, overall, the pain intensity of an intradermal injection of 2% lidocaine is low. The addition of sodium bicarbonate to 2% lidocaine decreases the pain associated with an intradermal skin wheal, and although the use of a 30-gauge needle decreases the pain of injection, the addition of sodium bicarbonate seems to have a greater overall effect than needle size. IMPLICATIONS: Forty volunteers randomly received four intradermal injections consisting of 2% lidocaine with or without sodium bicarbonate via a 25- or 30-gauge needle. The addition of bicarbonate had a greater overall effect than needle size in decreasing the pain associated with the intradermal injection of lidocaine.

Neither L-arginine nor L-NAME affects neurological outcome after global ischemia in cats.

BACKGROUND AND PURPOSE: We attempted to determine whether N-nitro-L-arginine methyl ester (L-NAME) would improve neurological outcome and whether L-arginine (L-ARG) would worsen neurological outcome after transient global ischemia. METHODS: Halothane-anesthetized cats (n = 6 for each group) were treated with intravenous saline, L-NAME (5 mg/kg or 10 mg/kg), or L-arginine (300 mg/kg) 30 minutes before 10 minutes of ischemia (temporary ligation of the left subclavian and brachiocephalic arteries with hemorrhagic hypotension to 50 mm Hg). At 30 minutes of reperfusion, cats in the L-ARG group were administered an additional 300 mg/kg dose of intravenous L-arginine. RESULTS: Time (mean +/- SE) to isoelectric electroencephalography was similar among groups (saline, 26 +/- 11 seconds; L-NAME-5, 15 +/- 4 seconds; L-NAME-10, 36 +/- 27 seconds; and L-ARG, 22 +/- 7 seconds). At 72 hours, reperfusion pathological injury was severe and neurological deficit score (mean, range) was similar among groups (saline, 38[11 to 70]; L-NAME-5, 52 [40 to 73]; L-NAME-10, 47 [23 to 70]; and L-ARG, 40 [0 to 79]). CONCLUSIONS: Nitric oxide is not important in the mechanism of brain injury after global ischemia in cats.

Postischemic brain injury is affected stereospecifically by pentazocine in rats.

We tested whether rats treated with the sigma1-receptor ligand, (+)-pentazocine, during transient focal ischemia would have a smaller volume of postischemic brain infarction than rats treated with the nonspecific opioid-receptor ligand (-)-pentazocine. Rats underwent focal cerebral ischemia using the filament occlusion technique for 2 h, followed by 22 h of reperfusion. Rats received (+) or (-)-pentazocine (n = 9 each group) at a dose of 2 mg x kg(-1) x h(-1) by continuous intravenous infusion from 1 h of ischemia to 22 h of reperfusion. Triphenyltetrazolium-determined infarction volume of ipsilateral striatum ([+]-pentazocine, 19 +/- 4 mm3, mean +/- SEM; [-]-pentazocine, 44 +/- 5 mm3) and cerebral cortex ([+]-pentazocine, 26 +/- 12 mm3; [-]-pentazocine, 134 +/- 29 mm3) was smaller in rats treated with (+) compared with (-)-pentazocine. Infarction volume in rats treated with (-)-pentazocine was also very similar to the infarction volume in saline-treated control rats from our previous study (striatum 44 +/- 4 mm3; hemisphere 136 +/- 27 mm3). These data indicate that sigma1-receptors may play an important role in the mechanism of injury both in cortex and striatum after 2 h of transient focal ischemia in rat.

Comparative analysis of brain protection by N-methyl-D-aspartate receptor antagonists after transient focal ischemia in cats.

OBJECTIVE: We tested the hypothesis that the administration of the competitive N-methyl-D-aspartate (NMDA) receptor antagonist 2R,4R,5S-(2-amino-4,5-(1,2-cyclohexyl)-7-phosphonoheptanoic acid) (NPC 17742) or cis-4-(phosphonomethyl) piperidine-2-carboxylic acid (CGS 19755) or the noncompetitive NMDA receptor antagonist dizocilpine (MK-801), at the appropriate doses, would all have efficacy in decreasing early postischemic brain injury in a feline model of transient focal ischemia. DESIGN: Prospective, randomized, controlled animal trial. SETTING: University research laboratory. SUBJECTS: Forty mixed-breed cats. INTERVENTIONS: Halothane-anesthetized cats underwent 90 mins of left middle cerebral artery occlusion plus 4 hrs of reperfusion. At 75 mins of ischemia, control cats received intravenous saline (n = 10). Experimental cats (n = 10 in each group) were treated with NPC 17742 (5 mg/kg bolus and 2.5 mg/kg/hr throughout reperfusion), MK-801 (5 mg/kg intravenous bolus), or CGS 19755 (40 mg/kg intravenous bolus) in a randomized fashion. MEASUREMENTS AND MAIN RESULTS: Microsphere-determined blood flow to the ipsilateral inferior temporal cortex and caudate nucleus decreased to the same extent during ischemia, and recovered to the same extent during early reperfusion, in the four groups. Triphenyltetrazolium-determined injury volume of the ipsilateral caudate nucleus in cats treated with NPC 17742 (105 +/- 25 [SEM] mm3), MK-801 (97 +/- 22 mm3), and CGS 19755 (97 +/- 13 mm3) was less than in control cats (198 +/- 21 mm3). Hemisphere injury volumes with NPC 17742 (1209 +/- 405 mm3) and MK-801 (1338 +/- 395 mm3) were less than that value in controls (2193 +/- 372 mm3), whereas injury volume with CGS 19755 (1553 +/- 519 mm3) treatment did not attain significance (p < .09). CONCLUSIONS: NMDA receptor activation during reperfusion may contribute to the progression of injury in ischemic border regions after 90 mins of transient focal ischemia in the cat. At the doses chosen, there appear to be no major differences in therapeutic efficacy for competitive and noncompetitive NMDA receptor antagonists.

Intravenous basic fibroblast growth factor decreases brain injury resulting from focal ischemia in cats.

BACKGROUND AND PURPOSE: We tested the hypothesis that intravenous administration of basic fibroblast growth factor (bFGF) during 4 hours of permanent focal ischemia would affect acute brain injury. METHODS: Halothane-anesthetized cats underwent left middle cerebral artery (MCA) occlusion for 4 hours. Control cats received diluent (n = 14). Experimental cats were treated with bFGF at a rate of 5 (n = 13), 50 (n = 13), or 250 microg/kg per hour (n = 9) intravenously beginning 60 minutes after initiation of ischemia and continuing until the end of the protocol. RESULTS: As measured by the microsphere method, blood flow to ipsilateral caudate nucleus and ipsilateral inferior temporal cortex was decreased similarly during ischemia, before drug administration, in all groups. Likewise, there was no difference in blood flow to ipsilateral caudate nucleus or inferior temporal cortex as a result of bFGF administration during MCA occlusion. Triphenyltetrazolium-determined injury volume of the ipsilateral cerebral cortex (control, 40+/-7%; bFGF 5 microg/kg per hour, 22+/-5%; bFGF 50 microg/kg per hour, 26+/-7%; bFGF 255 microg/kg per hour, 23+/-6% of ipsilateral cerebral cortex; mean+/-SEM) was less in cats treated with bFGF. There was no difference among groups in injury volume to caudate nucleus (control, 29+/-8%; bFGF 5 microg/kg per hour, 29+/-8%; bFGF 50 microg/kg per hour, 21+/-7%; bFGF 250 microg/kg per hour, 32+/-7% of ipsilateral caudate nucleus). Somatosensory evoked potential amplitude decreased similarly (to <20% of baseline amplitude in all groups) during MCA occlusion and was not altered by bFGF administration. CONCLUSIONS; These data indicate that systemic administration of bFGF ameliorates acute injury in the cerebral cortex without increasing blood flow during focal ischemia in cats. Because bFGF afforded protection when administered after the onset of ischemia, bFGF may provide its beneficial effect by limiting progression of injury in ischemic border regions.

Intraventricular dexmedetomidine decreases cerebral blood flow during normoxia and hypoxia in dogs.

We tested the hypothesis that a centrally administered alpha 2-receptor agonist could alter the cerebrovascular response to hypoxia, without evidence of systemic absorption of the drug. Beagle dogs were anesthetized with 1.4% isoflurane and exposed to hypoxic hypoxia (Pao2 approximately 22 mm Hg) before and after ventricular-cisternal perfusion with mock cerebrospinal fluid (CSF group, n = 5) or dexmedetomidine (100 micrograms/mL; total dose 300 micrograms; DEX group, n = 6). Cerebral perfusion pressure, Paco2 and arterial oxygen content were controlled and regional cerebral blood flow (CBF; microspheres) and global cerebral metabolic rate for oxygen consumption (CMRO2) were measured. In another group (n = 5), drug distribution under the experimental conditions was assessed by 3H-clonidine administered by ventricular-cisternal perfusion. In the mock CSF group, flow to the cerebral hemispheres increased during hypoxia under baseline conditions and after CSF infusion: 66 +/- 8 to 170 +/- 15 mL.min-1.100 g-1 (265% +/- 24% of baseline value), 83 +/- 9 to 154 +/- 14 mL.min-1.100 g-1 (201% +/- 54% of post-CSF infusion value). DEX decreased normoxic flow in the cerebral hemispheres from 76 +/- 6 to 44 +/- 4 ml.min-1.100 g-1 with decreases in other regions of similar magnitude. After DEX, the absolute flow in all regions during hypoxia was 52%-55% of that prior to DEX (P < 0.05). However, because DEX also decreased normoxic CBF, the percent increase in flow during hypoxia was similar before and after DEX. CMRO2 was not affected by hypoxia prior to DEX. However, after DEX, hypoxia caused a marked reduction in cerebral oxygen delivery (5.2 +/- 1.0 vs 13.7 +/- 2.3 ml.min-1.100 g-1 for the CSF group) and CMRO2 (2.5 +/- 0.6 vs 3.9 +/- 0.6 ml.min-1.100 g-1). Regional accumulation of intraventricularly administered 3H-clonidine was greatest in periventricular brain structures (e.g., caudate nucleus, dorsal brainstem), and the concentration in the cerebral cortex was approximately 1% of the concentration in the ipsilateral caudate nucleus. We conclude that centrally administered DEX reduces CBF during normoxia and prevents adequate oxygen delivery during hypoxia. The mechanism of DEX-induced CBF reduction is not metabolically mediated, since CMRO2 is maintained at control values during normoxia despite the significant blood flow reduction. We believe that the reduction in CMRO2 during hypoxia in DEX-treated dogs is the result of a reduction of oxygen delivery rather than the underlying mechanism for the observed reduction in CBF during hypoxia.

PPBP [4-phenyl-1-(4-phenylbutyl) piperidine] decreases brain injury after transient focal ischemia in rats.

BACKGROUND AND PURPOSE: We tested the hypothesis that intravenous administration of the potent sigma-receptor ligand 4-phenyl-1-(4-phenylbutyl) piperidine (PPBP) during transient focal ischemia would decrease postischemic brain infarction volume in rats. METHODS: Rats underwent intravascular focal ischemia for 2 hours followed by 22 hours of reperfusion. Halothane anesthesia was used only during initiation and cessation of ischemia. Rats received saline (n = 10) or 1 mumol/kg per hour PPBP (n = 10) by continuous intravenous infusion starting 1 hour after the initiation of ischemia and continuing through 22 hours of reperfusion. RESULTS: There was no difference between groups in blood pressure, arterial blood gas values, and body temperature. Triphenyltetrazolium-determined infarction volume of ipsilateral cerebral cortex (saline, 39 +/- 6%; PPBP, 21 +/- 7% of ipsilateral hemisphere; mean +/- SEM) and striatum (saline, 68 +/- 6%; PPBP, 33 +/- 8% of ipsilateral striatum) was smaller in rats treated with PPBP than in rats treated with saline. CONCLUSIONS: These data indicate that sigma-receptors may play an important role in the mechanism of injury both in cortex and striatum after 2 hours of transient focal ischemia in rats. Because PPBP afforded protection when administered at the end of ischemia and during reperfusion, sigma-receptors may influence the progression of injury in ischemic border regions.