Functional MRI at 4.7 Tesla of the Rat Brain during Electric Stimulation of Forepaw, Hindpaw, or Tail in Single- and Multislice Experiments

Spenger, Christian; Josephson, Anna; Klason, Tomas; Hoehn, Mathias; Schwindt, Wolfram; Ingvar, Martin; Olson, Lar̀s

doi:10.1006/exnr.2000.7524

Cited by 57 publications

(52 citation statements)

References 33 publications

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“…Thus, although smaller magnitude activations were sometimes present outside the somatosensory pathway, they were unlikely the result of pain. Of note, in an fMRI study performed at 4.7 T, Spenger et al (2000) also report highly variable activations outside the somatosensory pathway (with no changes in MABP and HR) during forepaw stimulation in rats under α-chloralose anesthesia previously optimized to eliminate pain response to electrical stimulation. Second, isoflurane also depresses cerebrovascular reactivity to CO 2 relative to awake conditions (Sicard et al, 2003) which may explain the stronger hypercapnic challenges required to derive M. In animal studies, 5% and 10% CO 2 challenges are commonly used with other anesthetics (Luo et al, 2003;Wu et al, 2002), and the former is frequently used in human studies (Davis et al, 1998;Hoge et al, 1999).…”

Section: Potential Drawbacks Of the Isoflurane-anesthetized Forepaw-smentioning

confidence: 92%

“…First, isoflurane suppresses neural activity which could explain the higher stimulation current needed relative to that used under α-chloralose (1.5-2.0 mA; Duong et al, 2000;Silva et al, 1999) which could potentially cause pain-induced changes in MABP and HR, as well as activation outside the somatosensory pathway. However, the applied current was previously optimized to elicit robust fMRI responses without producing sustained changes in MABP and HR which is interpreted as an absence of painful stimuli (Spenger et al, 2000). This anesthesia protocol used herein was also found to eliminate conscious response to noxious stimuli (tail pinching; Liu et al, 2004).…”

Section: Potential Drawbacks Of the Isoflurane-anesthetized Forepaw-smentioning

confidence: 99%

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

2005

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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 (CMRO 2 ) in spontaneously breathing rats under isoflurane anesthesia. Each animal was subjected to a baseline period of six inspired gas conditions (9% O 2 , 12% O 2 , 21% O 2 , 100% O 2 , 5% CO 2 , and 10% CO 2 ) 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% O 2 , 21% O 2 100% O 2 , and 5% CO 2 ) and were relatively independent of baseline physiology. Consistent with data obtained using well-established techniques, baseline and stimulus-evoked CMRO 2 were invariant across moderate physiological perturbations thereby supporting a CMRO 2 -fMRI technique for non-invasive CMRO 2 measurement. However, under 9% O 2 and 10% CO 2 , stimulus-evoked CBF and BOLD were substantially reduced and the CMRO 2 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.

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Section: Potential Drawbacks Of the Isoflurane-anesthetized Forepaw-smentioning

confidence: 92%

Section: Potential Drawbacks Of the Isoflurane-anesthetized Forepaw-smentioning

confidence: 99%

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

2005

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“…Previous studies of electrical mapping of the exposed brain have been confirmed using fMRI for cortical localisation of the body's surface. In the rat, fMRI has been successfully used for the mapping of the forepaw (Hyder et al, 1994;Masamoto et al, 2007;Van Camp et al, 2006), the hindpaw (Bock et al, 1998), the tail (Spenger et al, 2000) and the barrel zones of the whiskers (Lu et al, 2005) .…”

Section: Introductionmentioning

confidence: 99%

Propofol allows precise quantitative arterial spin labelling functional magnetic resonance imaging in the rat

et al. 2010

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M., Propofol allows precise quantitative arterial spin labelling functional magnetic resonance imaging in the rat, NeuroImage (2010), doi: 10.1016/j.neuroimage. 2010.03.024 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT

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“…Although the small size of the rodent brain initially made fMRI relatively challenging, recent progress in MR hardware and scanning sequences has overcome these difficulties to allow functional mapping of the brain in response to peripheral sensory stimulation (Spenger et al, 2000;Keilholz et al, 2004). Introduction of ␣-chloralose to animal anesthesia has helped to standardize the technique (Bock et al, 1998;Austin et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Blood Oxygenation Level-Dependent Visualization of Synaptic Relay Stations of Sensory Pathways along the Neuroaxis in Response to Graded Sensory Stimulation of a Limb

Lilja

Endo

Hofstetter

et al. 2006

Journal of Neuroscience

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Blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) was used to test at which levels of the neuroaxis signals are elicited when different modalities of sensory information from the limbs ascend to cortex cerebri. We applied graded electric stimuli to the rat hindlimbs and used echo-planar imaging to monitor activity changes in the lumbar spinal cord and medulla oblongata, where primary afferents of painful and nonpainful sensation synapse, respectively. BOLD signals were detected in ipsilateral lumbar spinal cord gray matter using sufficiently strong stimuli. Using stimuli well below the threshold needed for signals to be elicited in the spinal cord, we found BOLD responses in dorsal medulla oblongata. The distribution of these signals is compatible with the neuroanatomy of the respective synaptic relay stations of the corresponding sensory pathways. Hence, the sensory pathways conducting painful and nonpainful information were successfully distinguished. The fMRI signals in the spinal cord were markedly decreased by morphine, and these effects were counteracted by naloxone. We conclude that fMRI can be used as a reliable and valid method to monitor neuronal activity in the rat spinal cord and medulla oblongata in response to sensory stimuli. Previously, we also documented BOLD signals from thalamus and cortex. Thus, BOLD responses can be elicited at all principal synaptic relay stations along the neuroaxis from lumbar spinal cord to sensory cortex. Rat spinal cord fMRI should become a useful tool in experimental spinal cord injury and pain research.

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Functional MRI at 4.7 Tesla of the Rat Brain during Electric Stimulation of Forepaw, Hindpaw, or Tail in Single- and Multislice Experiments

Cited by 57 publications

References 33 publications

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

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

Propofol allows precise quantitative arterial spin labelling functional magnetic resonance imaging in the rat

Blood Oxygenation Level-Dependent Visualization of Synaptic Relay Stations of Sensory Pathways along the Neuroaxis in Response to Graded Sensory Stimulation of a Limb

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