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(Stroke. 1997;28:609-616.)
© 1997 American Heart Association, Inc.

Articles

Intravenous Basic Fibroblast Growth Factor Decreases Brain Injury Resulting From Focal Ischemia in Cats

Ameil Bethel, MD; Jeffrey R. Kirsch, MD; Raymond C. Koehler, PhD; Seth P. Finklestein, MD; Richard J. Traystman, PhD

From the Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins Medical Institutions, Baltimore, Md, and Department of Neurology, Massachusetts General Hospital, Boston, Mass (S.P.F.).

Correspondence to Richard J. Traystman, PhD, Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins Medical Institutions, 600 N Wolfe St, Blalock 1408, Baltimore, MD 21287. E-mail rjtrayst{at}gwgate1.jhmi.jhu.edu.

	Abstract

Top Abstract Introduction Materials and Methods Results Discussion References

 
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 µg/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 µg/kg per hour, 22±5%; bFGF 50 µg/kg per hour, 26±7%; bFGF 255 µg/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 µg/kg per hour, 29±8%; bFGF 50 µg/kg per hour, 21±7%; bFGF 250 µg/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.

Key Words: cerebral blood flow • growth factors • middle cerebral artery occlusion • neuroprotection • somatosensory evoked potentials • cats

	Introduction

Top Abstract Introduction Materials and Methods Results Discussion References

 
Immunoreactivity for bFGF increases in reactive astrocytes at the site of focal brain wounds¹ and in response to cerebral ischemia.² In addition, bFGF is a neurotrophic factor that supports survival of neurons in the central nervous system.³ In neuronal cell culture bFGF prevents neuronal death caused by hypoxia in a dose-dependent manner.⁴

The therapeutic efficacy of bFGF in vivo has been demonstrated by a number of laboratories through central administration of bFGF in rodent models of ischemia. For example, intracisternal administration of bFGF, starting 1 day after MCA occlusion in rats, decreased the degree of retrograde degeneration of thalamic neurons.⁵ Likewise, continuous intraventricular infusion of bFGF, starting 3 days before permanent MCA occlusion in rats, decreased infarct volume mea- sured 24 hours after initiation of ischemia.⁶ On the contrary, when intraventricular infusion of bFGF did not begin until 2 days after the onset of MCA occlusion in rats, there was no therapeutic benefit. In gerbils, central administration of bFGF^{7 8} or aFGF⁹ decreased brain injury associated with transient forebrain ischemia.

The potential therapeutic effect of systemically administered bFGF has only recently been evaluated. For example, in neonatal rats, pretreatment with bFGF by intraperitoneal administration was associated with decreased neuronal injury resulting from intrastriatal injection of NMDA or a transient hypoxic-ischemic insult.¹⁰ More recently, intravenous infusion of bFGF, beginning at the onset of reperfusion from transient focal ischemia¹¹ or within 5¹² or 30¹³ minutes after the onset of permanent ischemia in rats, attenuated brain injury. The present study was designed to evaluate the potential acute therapeutic effect of intravenous bFGF in a large animal model of permanent focal cerebral ischemia and determine whether any beneficial effect of systemically administered bFGF may be related to an acute alteration in distribution of CBF. CBF response to bFGF was also evaluated in a cohort of nonischemic cats to establish whether there was a dose range in which bFGF produced vascular effects independent of intervening ischemia and to determine how these doses may compare with the dose range required for cerebral protection.

	Materials and Methods

Top Abstract Introduction Materials and Methods Results Discussion References

 
The study was conducted in accordance with National Institutes of Health guidelines for the use of experimental animals, and the protocols were approved by the Institutional Animal Care and Use Committee.

Male cats were anesthetized with halothane in oxygen. They were orally intubated and mechanically ventilated to maintain PaCO₂ at approximately 35 to 40 mm Hg. Anesthesia was maintained with halothane (1.0% to 1.5%) in oxygen-enriched air (FiO₂, 0.35 to 0.40). The concentration of anesthetic was not altered during the experimental protocol. The skeletal muscle relaxant pancuronium bromide (0.2 mg/kg IV) was administered as a single dose to prevent movement during electrocautery and muscle artifact during evoked potential monitoring.

Both femoral veins were catheterized for infusion of lactated Ringer's solution and drugs. Catheters placed in the descending aorta through a femoral artery were used for blood pressure measurement, for arterial blood gas sampling, and for withdrawal of reference blood samples during injection of radiolabeled microspheres. After left thoracotomy, a catheter was inserted into the left atrium for injection of radiolabeled microspheres. The cat was turned prone and its head positioned in a stereotaxic frame approximately 4 cm higher than its heart. A thermistor placed in the right temporal epidural space was used to estimate brain temperature. Epidural temperature was maintained at 38.0±0.5°C with the use of a warming blanket and a heating lamp.

Arterial blood pressure was continuously monitored. Arterial pH, PaCO₂, and PaO₂ were measured with a self-calibrating electrode system (Radiometer ABL 3). Hemoglobin and arterial oxygen content were measured with a hemoximeter (Radiometer, model OSM3). Blood glucose was measured with a glucose analyzer (model 2300A, Yellow Springs Instruments). A multichannel signal averager (model CA-1000, Nicolet Biomedical Instruments) was used to measure the SEP with foreleg stimulation, as previously described.^{14 15} The amplitude to the peak of the first major negative wave was measured from the peak of the preceding positive wave.

Regional CBF was measured with radiolabeled microspheres (15.5±0.5 µm diameter; Du Pont–NEN Products) by the reference withdrawal method.¹⁶ Five of six radioactive isotopes (¹⁵³Gd, ^114mIn, ¹¹³Sn, ¹⁰³Ru, ⁹⁵Nb, or ⁴⁶Sc) were injected in random sequence into each animal. Approximately 1.5x10⁶ microspheres were injected into the left atrium over a 20-second period, followed by a 5-mL saline flush. Reference blood samples were withdrawn from the aorta at 1.9 mL/min beginning 30 seconds before the injection and continuing for 90 seconds after the saline flush.

Recombinant human bFGF was obtained as a lyophilized citrate/sucrose formulation (Scios Nova Inc). After reconstitution with sterile water, the stock solution of 2 mg/mL was stored at -80°C until the day of each experiment. Stock solution was then diluted into vehicle containing 0.9% NaCl and 100 µg/mL bovine serum albumin (Boeringer-Mannheim) (pH 7.4). The final concentration was adjusted so that the infusion rate was at 1 mL/kg per hour for each drug dose.

Two individual protocols were conducted. The first protocol (nonischemic protocol) was designed to determine the dose range for the cerebrovascular effects of bFGF during intravenous administration. The second protocol (ischemia protocol) was designed to determine whether there was a dose-response relationship for the effect of bFGF on brain injury after permanent focal cerebral ischemia at doses lower than the range found to produce cerebrovascular effects in the nonis-chemic protocol.

In the nonischemic protocol, baseline measurements were obtained 20 minutes after surgical preparation. In the placebo group (sham dose-escalation protocol), all measurements were made after 1 hour of intravenous infusion of diluent at three points in time to mimic the protocol for the low-dose and high-dose groups. In the low-dose group (n=4), all measurements were repeated after 1 hour of intravenous infusion of 5, 50, and 250 µg/kg per hour bFGF in a dose-escalation fashion. In the high-dose group (n=4), all measurements were repeated after 1 hour of intravenous infusion of 500, 750, and 1000 µg/kg per hour bFGF in a dose-escalation fashion. In two additional animals, baseline measurements were made 20 minutes after surgical preparation and then after 1 hour of infusion into the left atrium at a dose of 500, 750, and 1000 µg/kg per hour bFGF in a dose-escalation fashion. Infusion into the left atrium was used in an attempt to accentuate the concentration of bFGF presented to the brain. Data from the cats with infusion into the left atrium were combined with the data from cats receiving the same dose-escalation protocol through the intravenous route because there were no differences between groups.

In the ischemia protocol, the left MCA was exposed by a transorbital approach with the use of microsurgical techniques. Baseline measurements of all variables were obtained before excision of the dura. To produce focal ischemia, the left MCA was occluded near its origin from the intracranial carotid artery with the use of a microvascular clip for 240 minutes.^{14 17} Cats that did not achieve at least 75% reduction in SEP amplitude at 30 minutes of MCA occlusion were excluded from the protocol before randomization to a drug treatment group (n=8). At 60 minutes of ischemia, cats were assigned randomly to receive either diluent or bFGF at a dose of 5, 50, or 250 µg/kg per hour. In all cats diluent or drug was administered at a rate of 1 mL/kg per hour until 240 minutes of MCA occlusion. Investigators were blinded to treatment group until all data were analyzed. Repeated measurements of all variables were made at 30, 90, 150, and 240 minutes of left MCA occlusion. Cats that did not demonstrate adequate ischemia of the caudate nucleus ipsilateral to the occlusion (whole caudate nucleus blood flow 80 mL/min per 100 g; n=10) or ipsilateral inferior temporal cortex (blood flow 70 mL/min per 100 g; n=11) at 30 minutes after MCA occlusion (before drug administration) were excluded from further study.

At the end of each protocol, cats were killed with intravenous potassium chloride. In cats exposed to ischemia, the brain was removed and cut immediately into 12 uniform coronal sections 3 mm thick to estimate brain injury with the 2,3,5-triphenyltetrazolium chloride (Sigma Chemical Co) technique,^{18 19} as previously described.^{15 20} After injury volume was estimated, the slices of brain were placed in 10% buffered formalin for 1 to 2 days before they were sectioned for regional CBF measurement. Ipsilateral and contralateral temporal and parietal lobes of the middle four slices were sectioned into inferior temporal, temporoparietal, and parietal cortex; ipsilateral and contralateral caudate nucleus, brain stem, and cerebellum were also analyzed. The arterial microsphere reference samples and weighed tissue specimens were counted in a multichannel autogamma scintillation spectroscopy system, and blood flow was calculated by the reference sample technique.¹⁶

Values are expressed as mean±SEM. Statistical comparison to assess changes in measured physiological variables and CBF within groups was performed by repeated measures ANOVA. Comparison of physiological variables, blood flow, and injury volume among groups was achieved with one-way ANOVA. Post hoc analysis was performed with the Newman-Keuls test. ANCOVA was used to determine the effect of drug treatment on regional injury volume. Regional CBF in inferior temporal ischemic cortex at 30 minutes of ischemia (before drug administration) was used as a covariant for cortical injury. Caudate nucleus blood flow was used as a covariant for caudate injury. Statistical differences were considered significant at P<.05.

	Results

Top Abstract Introduction Materials and Methods Results Discussion References

 
In nonischemic cats there was no difference among groups in any physiological variable. MABP and SEP amplitude were similar among groups over the time course of the experiments (Fig 1). CBF was similar among groups under baseline conditions and was not affected by drug treatment in the cohort studied over the dose range used in the ischemia protocol (5, 50, and 250 µg/kg per hour). Cortical blood flow was higher in cats receiving 1000 µg/kg per hour (136±10 mL/min per 100 g) than in cats receiving placebo at the same point in the time sequence (79±12 mL/min per 100 g). However, there was no difference among groups in blood flow to brain stem. Based on these preliminary data, we chose to evaluate only the three lowest doses during ischemia to reduce the likelihood of an effect of bFGF on intrais-chemic CBF.

View larger version (53K): [in this window] [in a new window]   Figure 1. MABP, CBF to cerebrum, and SEP amplitude in nonischemic cats treated with placebo or bFGF under a dose-escalation protocol. Doses of bFGF administered were low-dose (5, 50, and 250 µg/kg per hour) or high-dose (500, 750, and 1000 µg/kg per hour) by intravenous infusion after baseline measurements were obtained. Placebo group acted as a sham dose-escalation group and only received diluent at each time interval. Values are mean±SEM.

There were no significant differences in baseline values of any physiological variables among the four experimental groups subjected to ischemia. Likewise, arterial blood gas values and hemoglobin and glucose concentrations were similar among groups throughout ische-mia. Although treatment with bFGF at a dose of 250 µg/kg per hour was associated with a reduction in MABP at 240 minutes of ischemia compared with the baseline value (118±5 to 102±6 mm Hg), there was no difference among groups at this time point (range, 101±7 to 107±7 mm Hg at 240 minutes of ischemia). Brain temperature was controlled at approximately 38°C in all groups.

Values of blood flow to brain regions ipsilateral to MCA occlusion and to the posterior fossa are given in the Table. Baseline blood flow was similar among groups, except in ipsilateral temporoparietal and parietal cortex, where it was higher in cats that subsequently were treated with bFGF at 250 µg/kg per hour. Reduction in cortical CBF during left MCA occlusion was graded. The greatest reduction occurred in ipsilateral inferior temporal cortex, and the smallest reduction was seen in parietal cortex. By chance, within each region, there was also some variability in the degree of blood flow reduction among groups. This variation was most evident in the ipsilateral temporoparietal cortex. For example, even before drug administration (30 minutes of ischemia) CBF was higher in the bFGF 250 µg/kg per hour group than in the control group. On the contrary, CBF to the ipsilateral inferior temporal cortex and caudate nucleus was similarly reduced in all groups during MCA occlusion.

View this table: [in this window] [in a new window]   Table 1. CBF to Ipsilateral Cortical Regions, Caudate Nucleus, and Posterior Fossa During Baseline and During 240 Minutes of Left MCA Occlusion in Cats Treated With Diluent (Control) or bFGF at 60 Minutes of Occlusion

Baseline amplitude (Fig 2) and latency (control, 12.0±0.1 ms; bFGF 5 µg/kg per hour, 12.1±0.2 ms; bFGF 50 µg/kg per hour, 12.6±0.1 ms; bFGF 250 µg/kg per hour, 12.0±0.03 ms) of the primary cortical SEP were not different among groups. Ipsilateral SEP amplitude decreased similarly in all groups during left MCA occlusion (control, 3±1% of baseline; bFGF 5 µg/kg per hour, 10±3% of baseline; bFGF 50 µg/kg per hour, 7±2% of baseline; bFGF 250 µg/kg per hour, 15±4% of baseline). Ipsilateral SEP amplitude did not recover throughout the period of left MCA occlusion. Contralateral SEP amplitude was not affected by MCA occlusion. All cats had normal latency of the wave measured over the second cervical vertebra throughout the protocol.

View larger version (16K): [in this window] [in a new window]   Figure 2. Amplitude of the primary SEP in cats exposed to 240-minute MCA occlusion. In each group drug infusion (placebo or bFGF) occurred between 60 and 240 minutes of MCA occlusion. bFGF was infused at 5 µg/kg per hour in the bFGF-5 group, 50 µg/kg per hour in the bFGF-50 group, and 250 µg/kg per hour in the bFGF-250 group. There was no difference among groups in degree of SEP amplitude reduction over the duration of the protocol.

Ipsilateral cerebral hemispheric injury volume was greater in the control group than in the bFGF 5 µg/kg per hour group (Fig 3). Higher doses of bFGF were not associated with any further reduction in hemispheric injury. Unlike the effect of bFGF in cerebral cortex, bFGF treatment did not reduce injury volume in caudate nucleus (Fig 3).

View larger version (44K): [in this window] [in a new window]   Figure 3. Injury volume of ipsilateral caudate nucleus and cerebral cortex in cats exposed to 240 minutes of left MCA occlusion. Values are expressed as percentage of ipsilateral volume with injury. In each group drug infusion (placebo or bFGF) occurred between 60 and 240 minutes of MCA occlusion. bFGF was infused at 5, 50, and 250 µg/kg per hour. *P<.05 versus placebo group.

	Discussion

Top Abstract Introduction Materials and Methods Results Discussion References

 
Intravenous administration of bFGF substantially reduced brain injury in cortex of cats exposed to 4 hours of MCA occlusion, even though continuous infusion did not start until 1 hour after the onset of ischemia. The effect of bFGF on brain injury was not correlated with alteration in SEP amplitude. Moreover, the mechanism by which bFGF minimizes brain injury during 4 hours of MCA occlusion is not related to a more favorable distribution of CBF. In cats not exposed to ischemia, a dose 200 times greater than the therapeutic dose was required to cause an increase in CBF.

bFGF is a neurotrophic factor that supports survival of neurons in the central nervous system.³ Binding and biological responsiveness to bFGF occurs through one of three FGF receptor families in brain: FGFR-1, FGFR-2, and FGFR-3.²¹ Although the regional brain distribution of these receptors has been evaluated,²¹ the functional significance of this distribution is less clearly understood.

A potential role for bFGF in the mechanism of brain injury is suggested by the finding that bFGF immunoreactivity occurs in models of brain injury.^{1 2} In a model of rose bengal–induced focal cerebral ischemia, an increase in bFGF mRNA expression began to occur in some regions as early as 4 hours after the onset of ischemia.²² In addition, the upregulation in bFGF gene expression was due to an upregulation in glial bFGF expression in most of the regions studied. Similarly, astrocytes demonstrate marked immunoreactivity for bFGF in areas of brain injury in stoke-prone spontaneously hypertensive rats.²³ Coincident with an increase in bFGF gene expression is also an increase in FGF receptor gene expression after focal ischemia.²⁴ It has been speculated that the stimulus for the increase in FGF receptor gene expression may be due to an action of a blood-borne macromolecule distributing to the peri-infarcted brain tissue.²⁴ Together these data suggest that bFGF may modulate brain injury after focal ischemia.

Several laboratories have evaluated the neuroprotective efficacy of FGF in vivo in rodent models of cerebral ischemia. Our demonstration of therapeutic benefit of bFGF in mixed-breed cats allows us to conclude that efficacy is not species dependent. In general, in rodents, bFGF has been demonstrated to have therapeutic efficacy in the setting of focal cerebral ischemia. In transgenic mice that express bovine bFGF there is less brain injury in response to a complex hypoxic-ischemic cerebral insult than a group of nontransgenic mice.²⁵ In gerbils, intraventricular pretreatment with bFGF⁷ or aFGF⁹ was associated with less ischemia-induced injury in hippocampus compared with concurrently tested controls. Consistent with an important role for bFGF in the mechanism of brain injury, Wen et al⁸ have demonstrated that ventricular administration of platelet factor 4, a putative bFGF receptor antagonist, or bFGF-neutralizing antibody exerts a neurotoxic effect in the setting of transient cerebral ischemia in gerbils. In rats, brain injury in response to focal ischemia is reduced when bFGF is administered into the cerebral spinal fluid space beginning either before ischemia⁶ or up to 1 day after occlusion.⁵ However, neurological injury was not reduced in rats that had intraventricular bFGF treatment beginning 2 days after the onset of MCA occlusion.²⁶

bFGF is a 154–amino acid, 18-kDa polypeptide that would not be expected to easily cross the blood-brain barrier. Therefore, if the therapeutic efficacy of bFGF depended on access of the compound to neurons or glia, systemic administration would be expected to have limited efficacy. Nonetheless, neonatal rats treated by intraperitoneal administration of bFGF before transient hypoxia-cerebral ischemia had less brain injury than control rats exposed to the same hypoxic-ischemic insult.¹⁰ In addition, in adult rats intravenous infusion of bFGF starting at the time of reperfusion from 2 hours of focal cerebral ischemia is associated with substantial reduction in brain injury.²⁷

Our study demonstrates that the therapeutic role of bFGF is not limited to rodents. In addition, in cats therapeutic efficacy is achieved despite intravenous administration that did not commence until 1 hour after the onset of ischemia. Efficacy by intravenous administration does not exclude a central site of action for this polypeptide because it is possible that the drug reaches the brain through a disrupted blood-brain barrier in the area of ischemia or by slow continuous central absorption.²⁸ Lack of a dose-response relationship in our study may suggest that the site of action for bFGF may be saturated even at the lowest dose used in the present study (5 µg/kg per hour). Saturation of receptors may subsequently prevent receptor dimerization and signaling.

At very high doses (1000 µg/kg per hour), bFGF prevented the decrease in CBF to cerebrum that normally occurs over time during inhalational anesthesia.²⁹ This is consistent with the finding of pial vessel dilation during topical application of bFGF^{11 30} and an increased flow in a brain region just outside an area of focal ischemia after intracarotid administration of bFGF.¹² However, in our study the dose of bFGF associated with an increase in CBF was not associated with an alteration in MABP. The difference between our study and that of Cuevas et al,³¹ which demonstrated a reduction in MABP during bFGF administration, is that in our study bFGF was administered by continuous intravenous infusion rather than by bolus injection, as was used by Cuevas et al. This lack of an effect of bFGF on MABP in our study argues against the possibility that bFGF is working to increase CBF, at high doses, through a mechanism involving diffuse release or production of nitric oxide. In addition, because the dose of bFGF found to be therapeutic in our model of focal ischemia did not increase CBF in the nonischemic cats or cause a redistribution of CBF in cats exposed to MCA occlusion, we conclude that the protective effects of bFGF are unrelated to any effects on regional CBF.

For microsphere analysis of blood flow, we sectioned coronal slices into inferior, lateral, and superior portions of cortex to ensure an adequate number of microspheres. It is possible that subtle differences among groups in blood flow in border regions were not detected when this amount of tissue was pooled together. However, the microsphere techniques permitted repeated measurements, and we found no significant increase in intraischemic CBF on a paired basis after bFGF administration. A focal increase in CBF only in border regions would have had to be confined to a relatively small region to be undetectable statistically on a paired basis. Consistent with this possibility is the finding of an increase in transitional zone blood flow resulting from bFGF administration in rats.¹²

The therapeutic efficacy of bFGF in the cat model of 4-hour MCA occlusion may be related to an interaction with NMDA receptor signal transduction. In the in vitro setting, bFGF raises the threshold for glutamate toxicity, antagonizes the outgrowth-inhibiting action of glutamate, and reduces glutamate-induced increases in intracellular calcium levels.³² These protective actions in regard to bFGF glutamate neurotoxicity have been attributed to an interaction of bFGF with the NMDA receptor transduction pathway because it reduced glutamate- and quinolinic acid–induced neurotoxicity but had little effect on kainic acid–induced neurotoxicity in vitro.³³ The mechanism for protection by bFGF on glutamate-induced neurodegeneration also appears to be dependent on its ability to initiate synthesis of some protein moiety within the neuron.³² Consistent with the hypothesis that bFGF is protective during ischemia by counteracting an effect of NMDA receptor stimulation is the finding that bFGF³⁴ also protects neurons exposed to iron-induced degeneration, an injury that is also prevented by NMDA receptor antagonists. In addition, systemic administration of bFGF dramatically reduces neuronal injury associated with intrastriatal injection of NMDA.¹⁰

Removal of growth factors in neuronal cell culture can induce programmed cell death. In the setting of focal ischemia in border regions where there may be loss of endogenous growth factor production, ischemia-induced calcium increases may accelerate cell death. It is possible that stimulation of bFGF receptors prevents this accumulation. Longer survival studies are required to determine whether bFGF prevents or merely delays cell death in ischemic border regions.

In conclusion, intravenous bFGF minimizes brain injury in cats exposed to 4 hours of MCA occlusion, even when administration is delayed until 1 hour after the onset of ischemia. The effect of bFGF on brain injury is not correlated with alteration in SEP amplitude. The mechanism by which bFGF minimizes brain injury during 4 hours of MCA occlusion is not related to a more favorable distribution of CBF. If the efficacy of bFGF in the setting of focal cerebral ischemia is related to an effect on the NMDA receptor, subsequent studies should determine whether it offers any additional protection when it is combined with currently available competitive NMDA receptor antagonists. Like bFGF, competitive NMDA receptor antagonists have significant efficacy for brain protection during MCA occlusion in cats.³⁵

	Selected Abbreviations and Acronyms

 

CBF = cerebral blood flow FGF = fibroblast growth factor aFGF = acidic FGF bFGF = basic FGF MABP = mean arterial blood pressure MCA = middle cerebral artery NMDA = N-methyl-D-aspartate SEP = somatosensory evoked potential

	Acknowledgments

 
This study was supported in part by US Public Health Service, National Institutes of Health grant NS20020. Dr Traystman's laboratory received bFGF and financial support from Scios Nova Inc, Mountain View, Calif. Dr Finklestein has applied for patent rights for the use of bFGF in the treatment of stroke. The authors thank Ying Wu and Denise Ott for excellent technical assistance and Candy Berryman for excellent secretarial assistance.

Received July 10, 1996; revision received October 2, 1996; accepted October 25, 1996.

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