Enhancement in cognitive function recovery by granulocyte-colony stimulating factor in a rodent model of traumatic brain injury.

Traumatic brain injury (TBI) is characterized by neuronal damage and commonly, secondary cell death, leading to functional and neurological dysfunction. Despite the recent focus of TBI research on developing therapies, affective therapeutic strategies targeting neuronal death associated with TBI remain underexplored. This study explored the efficacy of granulocyte-colony stimulating factor (G-CSF) as an intervention for improving cognitive deficits commonly associated with TBI. Although G-CSF has been studied with histological techniques, to date, its effects on functional outcome remain unknown. To this end, we used a closed head injury (CHI) model in Wistar rats that were randomly assigned to one of four groups (untreated TBI, G-CSF treated TBI, G-CSF treated Control, Control). The treatment groups were administered subcutaneous injections of G-CSF 30 min (120 µg/kg) and 12 h (60 µg/kg) post-trauma. The Morris Water Maze test was used to measure any treatment-associated changes in cognitive deficits observed in TBI animals at days 2-6 post-injury. Our findings demonstrate a significant improvement in cognitive performance in the G-CSF treated TBI animals within a week of injury, compared to untreated TBI, indicative of immediate and beneficial effect of G-CSF on cognitive performance post CHI. Our model suggests that early G-CSF exposure may be a promising therapeutic approach in recovery of cognitive deficits due to TBI.

Multi-modal approach for investigating brain and behavior changes in an animal model of traumatic brain injury.

Use of novel approaches in imaging modalities is needed for enhancing diagnostic and therapeutic outcomes of persons with a traumatic brain injury (TBI). This study explored the feasibility of using functional magnetic resonance imaging (fMRI) in conjunction with behavioral measures to target dynamic changes in specific neural circuitries in an animal model of TBI. Wistar rats were randomly assigned to one of two groups (traumatic brain injury/sham operation). TBI rats were subjected to the closed head injury (CHI) model. Any observable motor deficits and cognitive deficits associated with the injury were measured using beam walk and Morris water maze tests, respectively. fMRI was performed to assess the underlying post-traumatic cerebral anatomy and function in acute (24 hours after the injury) and chronic (7 and 21 days after the injury) phases. Beam walk test results detected no significant differences in motor deficits between groups. The Morris water maze test indicated that cognitive deficits persisted for the first week after injury and, to a large extent, resolved thereafter. Resting state functional connectivity (rsFC) analysis detected initially diminished connectivity between cortical areas involved in cognition for the TBI group; however, the connectivity patterns normalized at 1 week and remained so at the 3 weeks post-injury time point. Taken together, we have demonstrated an objective in vivo marker for mapping functional brain changes correlated with injury-associated cognitive behavior deficits and offer an animal model for testing potential therapeutic interventions options.

Visualization of clot lysis in a rat embolic stroke model: application to comparative lytic efficacy.

BACKGROUND AND PURPOSE: The purpose of this study was to develop a novel MRI method for imaging clot lysis in a rat embolic stroke model and to compare tissue plasminogen activator (tPA)-based clot lysis with and without recombinant Annexin-2 (rA2). METHODS: In experiment 1 we used in vitro optimization of clot visualization using multiple MRI contrast agents in concentrations ranging from 5 to 50 µL in 250 µL blood. In experiment 2, we used in vivo characterization of the time course of clot lysis using the clot developed in the previous experiment. Diffusion, perfusion, angiography, and T1-weighted MRI for clot imaging were conducted before and during treatment with vehicle (n=6), tPA (n=8), or rA2 plus tPA (n=8) at multiple time points. Brains were removed for ex vivo clot localization. RESULTS: Clots created with 25 µL Magnevist were the most stable and provided the highest contrast-to-noise ratio. In the vehicle group, clot length as assessed by T1-weighted imaging correlated with histology (r=0.93). Clot length and cerebral blood flow-derived ischemic lesion volume were significantly smaller than vehicle at 15 minutes after treatment initiation in the rA2 plus tPA group, whereas in the tPA group no significant reduction from vehicle was observed until 30 minutes after treatment initiation. The rA2 plus tPA group had a significantly shorter clot length than the tPA group at 60 and 90 minutes after treatment initiation and significantly smaller cerebral blood flow deficit than the tPA group at 90 minutes after treatment initiation. CONCLUSIONS: We introduce a novel MRI-based clot imaging method for in vivo monitoring of clot lysis. Lytic efficacy of tPA was enhanced by rA2.

Emerging drugs for acute ischemic stroke.

Stroke is no longer an untreatable condition, and its management is changing rapidly as new developments appear for acute treatments. The objective of this article is to provide a concise introduction to the pathophysiology and existing treatments for stroke, as well as discussing current research goals and interventions under evaluation, along with potential development issues. It will end with the authors' interpretations of the presented material and their opinions about where the field is going, or should go, in the coming years. The material herein is derived from current literature and expert opinion. Overall, the most important findings are that future advances in stroke treatment will probably include combination therapies that will be administered in specialized stroke care units to maximize patient outcome.

Animal models of focal brain ischemia.

Stroke is a leading cause of disability and death in many countries. Understanding the pathophysiology of ischemic injury and developing therapies is an important endeavor that requires much additional research. Animal stroke models provide an important mechanism for these activities. A large number of stroke models have been developed and are currently used in laboratories around the world. These models are overviewed as are approaches for measuring infarct size and functional outcome.

Differential recovery of behavioral status and brain function assessed with functional magnetic resonance imaging after mild traumatic brain injury in the rat.

OBJECTIVE: The relationship between cerebral integrity, recovery of brain function, and neurologic status after mild traumatic brain injury is incompletely characterized. DESIGN: Prospective and randomized study in rodents. SETTING: University laboratory. SUBJECTS: Male Wistar rats (290-310 g). INTERVENTIONS: In rats, quantitative diffusion weighted imaging (DWI), perfusion weighted imaging (PWI), T2-weighted imaging (T2WI), and functional magnetic resonance imaging (fMRI) were performed up to 21 days after weight-induced, closed-head, mild traumatic brain injury (MTBI, n = 6) or sham operation (n = 6). Pixel-by-pixel analysis and region of interest analysis were used to evaluate structural (apparent diffusion coefficient [ADC] and basal cerebral blood flow [bCBF]) and functional magnetic resonance signal changes within the brain, respectively. Quantitative fMRI signal changes were correlated with behavioral measures. MEASUREMENTS AND MAIN RESULTS: Despite normal appearing DWI and T2WI findings following MTBI, persistent hypoperfusion developed that was not associated with cytotoxic edema. In contrast, the ADC was significantly increased by approximately 5% at 1 and 7 days post-MTBI. Post-MTBI fMRI responses to hypercapnia and forepaw stimulation were significantly impaired and showed a differential recovery rate between and within investigated region of interests. Significant dysfunction in forepaw placement test persisted up to day 1 and correlated significantly with fMRI signal changes in the primary somatosensory and motor cortices. CONCLUSIONS: MTBI produced distinct changes on multimodal MRI and behavioral variables acutely and chronically. Following MTBI, fMRI and ADC-bCBF pixel-by-pixel analysis identified subtle structural and functional alterations in the brain that appeared completely normal on conventional DWI and T2WI after concussion injury. The former techniques may therefore provide great potential for understanding mild traumatic brain injury, identifying mechanisms underlying recovery, and investigating specific interventions to enhance functional outcome.

Spectacular shrinking deficit: insights from multimodal magnetic resonance imaging after embolic middle cerebral artery occlusion in Sprague-Dawley rats.

Almost no data is available on the serial changes in the brain after spectacular shrinking deficit (SSD) that may help understand this relatively rare clinical phenomenon. Quantitative diffusion-(DWI), perfusion-(PWI), T(1)-(T1WI), T(2)-weighted (T2WI), and functional magnetic resonance imaging (fMRI) were performed before, during, and up to 7 days after embolic middle cerebral artery occlusion (eMCAO) in male Sprague-Dawley rats (n=9). Region of interest (ROI) analysis was used to evaluate structural and functional MR signal changes within three ROIs defined by the apparent diffusion coefficient (ADC), cerebral blood flow (CBF) signatures, and final tissue viability. DWI, PWI, and T2WI lesion volumes were calculated using previously established viability thresholds and final infarct volumes ascertained with 2,3,5-triphenyltetrazolium chloride (TTC) staining. Serial MRI demonstrated spontaneous reperfusion of initially hypoperfused MCA regions accompanied by substantial reduction of initial ADC and CBF lesions and gradual recovery of neurological outcome. Recovery rates of CBF/ADC abnormalities differed among ROIs. Functional magnetic resonance imaging showed persistent tissue dysfunction after the recovery of the CBF/ADC lesions. This study may facilitate our understanding of the pathophysiological mechanisms by which early, spontaneous reperfusion affects tissue fate and neurological function.

Normobaric hyperoxia delays perfusion/diffusion mismatch evolution, reduces infarct volume, and differentially affects neuronal cell death pathways after suture middle cerebral artery occlusion in rats.

Normobaric hyperoxia (NBO) has been shown to extend the reperfusion window after focal cerebral ischemia. Employing diffusion (DWI)- and perfusion (PWI)-weighted magnetic resonance imaging (MRI), the effect of NBO (100% started at 30 mins after middle cerebral artery occlusion (MCAO)) on the spatiotemporal evolution of ischemia during and after permanent (pMCAO) and transient suture middle cerebral artery occlusion (tMCAO) was investigated (experiment 3). In two additional experiments, time window (experiment 1) and cell death pathways (experiment 2) were investigated in the pMCAO model. In experiment 1, NBO treatment reduced infarct volume at 24 h after pMCAO by 10% when administered for 3 h (P>0.05) and by 44% when administered for 6 h (P<0.05). In experiment 2, NBO acutely (390 mins, P<0.05) reduced in situ end labeling (ISEL) positivity in the ipsilesional penumbra but increased contralesional necrotic as well as caspase-3-mediated apoptotic cell death. In experiment 3, CBF characteristics and CBF-derived lesion volumes did not differ between treated and untreated animals, whereas the apparent diffusion coefficient (ADC)-derived lesion volume essentially stopped progressing during NBO treatment, resulting in a persistent PWI/DWI mismatch that could be salvaged by delayed (3 h) reperfusion. In conclusion, NBO (1) acutely preserved the perfusion/diffusion mismatch without altering CBF, (2) significantly extended the time window for reperfusion, (3) induced lasting neuroprotection in permanent ischemia, and (4) although capable of reducing cell death in hypoperfused tissue it also induced cell death in otherwise unaffected areas. Our data suggest that NBO may represent a promising strategy for acute stroke treatment.

Long-term changes of functional MRI-based brain function, behavioral status, and histopathology after transient focal cerebral ischemia in rats.

BACKGROUND AND PURPOSE: The relation between recovery of brain function and neurological status after clinical and experimental cerebral ischemia is incompletely characterized. We assessed the evolution of ischemic injury, behavioral status, and brain activity at acute to chronic periods after transient middle cerebral artery occlusion (tMCAO) in rats. METHODS: Male Sprague-Dawley rats were subjected to 20-minute tMCAO (n=10) or sham operation (n=10). Sensorimotor behavioral testing and multimodal (diffusion, perfusion, T2, and functional) MRI, as well as postmortem hematoxylin-eosin staining, were performed before and up to 21 days after tMCAO. MRI and histological parameters were evaluated in 5 regions of interest within the sensorimotor network. Diffusion, perfusion, and T2 lesion volumes were calculated according to previously established viability thresholds. RESULTS: Diffusion and perfusion lesions were present during occlusion but disappeared completely and permanently within 30 minutes after reperfusion, with no T2 lesions seen. Functional MRI and behavioral deficits did not normalize until 1 and 21 days after tMCAO, respectively. Histology demonstrated selective neuronal cell death at 7 and 21 days after reperfusion. CONCLUSIONS: Twenty-minute tMCAO produced distinct changes on multimodal MRI, histology, and behavioral parameters acutely and chronically. Normal findings on MRI after transient ischemia may not indicate normal tissue status, as behavioral and histological anomalies remain. Behavioral dysfunction persisting long after the recovery of MRI parameters may relate to the subtle neuronal damage seen on histology. Together, these results may help explain unremitting neurological deficits in stroke or transient ischemic attack patients with normal MRI findings.

Neuroprotective effect of hyperbaric oxygen therapy monitored by MR-imaging after embolic stroke in rats.

The potential neuroprotective effects of hyperbaric oxygen (HBO) were tested in an embolic model of focal cerebral ischemia with partially spontaneous reperfusion. Rats (n = 10) were subjected to embolic middle cerebral artery occlusion (MCAO) and diffusion weighted MRI (DWI) was performed at baseline, 1, 3, and 6 h after MCAO to determine the ADC viability threshold yielding the lesion volumes that best approximated the 2,3,5-triphenyltetrazolium chloride (TTC) infarct volumes at 24 h (experiment 1). For assessment of neuroprotective effects, rats were treated with 100% oxygen at 2.5 atmospheres absolute (ATA, n = 15) or normobaric room air (n = 15) for 60 min beginning 180 min after MCAO (experiment 2). DWI-, perfusion (PWI)- and T2-weighted MRI (T2WI) started within 0.5 h after MCAO and was continued 5 h, 24 h (PWI and T2WI only), and 168 h (T2WI only). Infarct volume was calculated based on TTC-staining at 24 h (experiment 1) or 168 h (experiment 2) post-MCAO. ADC-lesion evolution was maximal between 3 and 6 h. In experiment 2, the relative regional cerebral blood volume (rCBV) of both groups showed similar incomplete spontaneous reperfusion in the ischemic core. HBO reduced infarct volume to 145.3 +/- 39.6 mm3 vs. 202.5 +/- 58.3 mm3 (control, P = 0.029). As shown by MRI and TTC, HBO treatment demonstrated significant neuroprotection at 5 h after embolic focal cerebral ischemia that lasted for 168 h.

Differential recovery of multimodal MRI and behavior after transient focal cerebral ischemia in rats.

The association between recovery of brain function and behavior after transient cerebral ischemia in animals and humans is incompletely characterized. Quantitative diffusion- (DWI), perfusion- (PWI), T(2)-weighted (T(2)WI), and functional magnetic resonance imaging (fMRI) were performed before, during, and up to 1 day after 20-mins transient middle cerebral artery occlusion (tMCAO; n=6) or sham operation (n=6) in male Sprague-Dawley rats. Viability thresholds were employed to calculate diffusion, perfusion, and T(2) lesion volumes. Region of interest analysis was used to evaluate structural and functional MR signal changes within the sensorimotor network, which were then related to corresponding behavioral measures. Post-mortem 2,3,5-triphenyltetrazolium chloride (TTC) staining was performed 24 h after ischemia. Transient middle cerebral artery occlusion produced lesions on DWI and PWI, which fully recovered by 30 mins after reperfusion. Ipsilesional fMRI responses to hypercapnia and forepaw stimulation were significantly impaired after ischemia and did not fully normalize until 3 and 24 h after tMCAO, respectively. No abnormalities were observed on imaging or TTC at 24 h despite significant behavioral dysfunctions including contralesional forelimb impairment and ipsilesional neglect. No MRI, behavioral, or TTC anomalies were observed in sham-operated rats. There were no significant correlations between MRI parameters, behavior, and TTC in either group. Together, these results suggest that normal findings on diffusion, perfusion, and T(2) imaging shortly after transient ischemia may not indicate normal tissue status as indicated by fMRI and behavior, which may help explain the persistence of neurologic deficits in patients with normal conventional MRI after cerebral ischemia.

Hemodynamic and metabolic changes induced by cocaine in anesthetized rat observed with multimodal functional MRI.

RATIONALE: Physiological changes (such as heart rate and respiration rate) associated with strong pharmacological stimuli could change the blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) mapping signals, independent of neural activity. OBJECTIVES: This study investigates whether the physiological changes per se associated with systemic cocaine administration (1 mg/kg) contaminate the BOLD fMRI signals by measuring BOLD and cerebral blood flow (CBF) fMRI and estimating the cerebral metabolic rate of oxygen (CMRO(2)) changes. MATERIALS AND METHODS: BOLD and CBF fMRI was performed, and changes in CMRO(2) were estimated using the BOLD biophysical model. RESULTS: After systemic cocaine administration, blood pressure, heart rate, and respiration rate increased, fMRI signals remained elevated after physiological parameters had returned to baseline. Cocaine induced changes in the BOLD signal within regions of the reward pathway that were heterogeneous and ranged from -1.2 to 5.4%, and negative changes in BOLD were observed along the cortical surface. Changes in CBF and estimated CMRO(2) were heterogeneous and positive throughout the brain, ranging from 14 to 150% and 10 to 55%, respectively. CONCLUSIONS: This study demonstrates a valuable tool to investigate the physiological and biophysical basis of drug action on the central nervous system, offering the means to distinguish the physiological from neural sources of the BOLD fMRI signal.

Comparison of ischemic lesion evolution in embolic versus mechanical middle cerebral artery occlusion in Sprague Dawley rats using diffusion and perfusion imaging.

BACKGROUND AND PURPOSE: Differences among models in the temporal evolution of ischemia after middle cerebral artery occlusion (MCAO) in rats may considerably influence the results of experimental stroke research. Using diffusion and perfusion imaging, we compared the spatiotemporal evolution of ischemia in Sprague Dawley rats after permanent suture MCAO (sMCAO; n=8) and embolic MCAO (eMCAO; n=8). METHODS: Serial measurements of quantitative cerebral blood flow (CBF) and the apparent diffusion coefficient (ADC) were performed up to 180 minutes after MCAO. ADC and CBF values within 5 different brain regions were analyzed. ADC and CBF lesion volumes were calculated by using previously established viability thresholds and correlated with infarct volume defined by 2,3,5-triphenyltetrazolium chloride staining 24 hours after MCAO. RESULTS: Compared with sMCAO animals, the threshold-derived CBF lesion volume was significantly larger in eMCAO at all time points (P<0.01), remained relatively constant over time, and was highly correlated with the 2,3,5-triphenyltetrazolium chloride-defined infarct size. The ADC lesion volume did not differ between models at any time point. A diffusion/perfusion mismatch was present significantly longer in eMCAO animals (P<0.05), and these rats demonstrated larger absolute mismatch volumes that were statistically significant at 30, 60, and 90 minutes (P<0.05). In both models, CBF and ADC declines were highly correlated. CONCLUSIONS: This study demonstrated substantial differences in acute ischemic lesion evolution between the eMCAO and sMCAO models.

A new model of thromboembolic stroke in the posterior circulation of the rat.

The prognosis of vertebrobasilar occlusion is grave and therapeutic options are limited. The aim of the present study was to develop a new model of embolic hindbrain ischemia in the rat that closely resembles the clinical situation and that can be used to study pathophysiology and treatment options. After thoracotomy in 20 male Wistar rats, 15 animals received an injection of in vitro prepared autologous blood clots into the left vertebral artery. Five animals without clot injection served as controls. Neurological deficits were assessed in all animals 2 h after embolism. After 2 h, five animals were sacrificed to measure cerebral blood flow (CBF) by iodo-antipyridine autoradiography, and to calculate early cerebellar swelling by comparison of both hemispheres in brain slices. In these animals, autoradiography revealed ipsilesional brain swelling and significantly reduced blood flow values relative to the contralateral (unaffected) structures. Immunohistology showed the typical pattern of focal cerebral ischemia in the brain stem and/or cerebellum in 7 of 10 animals allowed to recover to 24 h. Hence, successful thromboembolism was achieved in 12 of 15 animals (80%). With this novel model, the pathophysiology and potential treatments of posterior circulation stroke can be investigated.

The proteasome inhibitor VELCADE reduces infarction in rat models of focal cerebral ischemia.

The potential neuroprotective effects of VELCADE were investigated in two different models of focal cerebral ischemia. For time-window assessment, male Wistar-Kyoto rats were treated with 0.2 mg/kg VELCADE at 1, 2, or 3 h after the induction of permanent middle cerebral artery occlusion (MCAO) using the suture occlusion method (experiment 1). To evaluate effects in a different model, male Sprague-Dawley rats received 0.2 mg/kg VELCADE after embolic MCAO (experiment 2). Infarct volume was calculated based on TTC-staining 24 h postischemia and whole blood proteasome activity was fluorometrically determined in both experiments at baseline, 1 and 24 h post-MCAO. In experiment 1, a dose of 0.2 mg/kg inhibited proteasome activity by 77% and infarct volume was reduced to 175.7+/-59.9 mm3 and 205.9+/-83.9 mm3 (1 and 2 h group, respectively; p<0.05) compared to 306.5+/-48.5 mm3 (control). Treatment at 3 h was not neuroprotective (293.0+/-40.1 mm3). After embolic MCAO, infarct volume was 167.5+/-90.7 mm3 (treatment group) and 398.9+/-141.3 mm3 (control; p=0.002). In conclusion, VELCADE treatment inhibited whole blood proteasome activity and achieved significant neuroprotection in two rat models of focal cerebral ischemia at various time points poststroke.

Impaired spatial learning in a novel rat model of mild cerebral concussion injury.

The aim of the present study was to develop a model of mild traumatic brain injury in the rat that mimics human concussive brain injury suitable to study pathophysiology and potential treatments. 34 male Wistar rats received a closed head trauma (TBI) and 30 animals served as controls (CON). Immediately following trauma, animals lost their muscle tone and righting reflex response, recovering from the latter within 11.4 +/- 8.2 min. Corneal reflex and whisker responses returned within 4.5 +/- 3.0 min and 6.1 +/- 2.9 min, respectively. The impact resulted in a short transient decrease of pO2 (P < 0.001), increase in mean arterial blood pressure (P = 0.026), and a reduction of heart rate (P < 0.01). Serial MRI did not show any abnormalities across the entire cerebrum on diffusion, T1, T2, and T2*-weighted images at all investigated time points. TBI animals needed significantly longer to locate the hidden platform in a Morris water maze and spent less time in the training quadrant than controls. TBI led to a significant neuronal loss in frontal cortex (P < 0.001), as well as hippocampal CA3 (P = 0.017) and CA1 (P = 0.002) at 9 days after the trauma; however, cytoskeletal architecture was preserved as indicated by normal betaAPP- and MAP-2 staining. We present a unique, noninvasive rat model of mild closed head trauma with characteristics of human concussion injury, including brief loss of consciousness, cognitive impairment, and minor brain injury.

Effects of hypoxia, hyperoxia, and hypercapnia on baseline and stimulus-evoked BOLD, CBF, and CMRO2 in spontaneously breathing animals.

Functional magnetic resonance imaging (fMRI) was used to investigate the effects of inspired hypoxic, hyperoxic, and hypercapnic gases on baseline and stimulus-evoked changes in blood oxygenation level-dependent (BOLD) signals, cerebral blood flow (CBF), and the cerebral metabolic rate of oxygen (CMRO2) in spontaneously breathing rats under isoflurane anesthesia. Each animal was subjected to a baseline period of six inspired gas conditions (9% O2, 12% O2, 21% O2, 100% O2, 5% CO2, and 10% CO2) followed by a superimposed period of forepaw stimulation. Significant stimulus-evoked fMRI responses were found in the primary somatosensory cortices. Relative fMRI responses to forepaw stimulation varied across gas conditions and were dependent on baseline physiology, whereas absolute fMRI responses were similar across moderate gas conditions (12% O2, 21% O2 100% O2, and 5% CO2) and were relatively independent of baseline physiology. Consistent with data obtained using well-established techniques, baseline and stimulus-evoked CMRO2 were invariant across moderate physiological perturbations thereby supporting a CMRO2-fMRI technique for non-invasive CMRO2 measurement. However, under 9% O2 and 10% CO2, stimulus-evoked CBF and BOLD were substantially reduced and the CMRO2 formalism appeared invalid, likely due to attenuated neurovascular coupling and/or a failure of the model under extreme physiological perturbations. These findings demonstrate that absolute fMRI measurements help distinguish neural from non-neural contributions to the fMRI signals and may lend a more accurate measure of brain activity during states of altered basal physiology. Moreover, since numerous pharmacologic agents, pathophysiological states, and psychiatric conditions alter baseline physiology independent of neural activity, these results have implications for neuroimaging studies using relative fMRI changes to map brain activity.

Imaging oxygen consumption in forepaw somatosensory stimulation in rats under isoflurane anesthesia.

The cerebral metabolic rate of oxygen (CMRO2) was dynamically evaluated on a pixel-by-pixel basis in isoflurane-anesthetized and spontaneously breathing rats following graded electrical somatosensory forepaw stimulations (4, 6, and 8 mA). In contrast to alpha-chloralose, which is the most widely used anesthetic in forepaw-stimulation fMRI studies of rats under mechanical ventilation, isoflurane (1.1-1.2%) provided a stable anesthesia level over a prolonged period, without the need to adjust the ventilation volume/rate or sample blood gases. Combined cerebral blood flow signals (CBF) and blood oxygenation level-dependent (BOLD) fMRI signals were simultaneously measured with the use of a multislice continuous arterial spin labeling (CASL) technique (two-coil setup). CMRO2 was calculated using the biophysical BOLD model of Ogawa et al. (Proc Natl Acad Sci USA 1992;89:5951-5955). The stimulus-evoked BOLD percent changes at 4, 6, and 8 A were, respectively, 0.5% +/- 0.2%, 1.4% +/- 0.3%, and 2.0% +/- 0.3% (mean +/- SD, N = 6). The CBF percent changes were 23% +/- 6%, 58% +/- 9%, and 87% +/- 14%. The CMRO2 percent changes were 14% +/- 4%, 24% +/- 6%, and 43% +/- 11%. BOLD, CBF, and CMRO2 activations were localized to the forepaw somatosensory cortices without evidence of plateau for oxygen consumption, indicative of partial coupling of CBF and CMRO2. This study describes a useful forepaw-stimulation model for fMRI, and demonstrate that CMRO2 changes can be dynamically imaged on a pixel-by-pixel basis in a single setting with high spatiotemporal resolution.