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Spectral analysis of cardiovascular control after spinal cord injury in rats: Effect of time post-injury
Abstracts / Autonomic Neuroscience: Basic and Clinical 163 (2011) 1–133
Neurology 2010), expand the technique to light microscopy, use TH and DβH to stain for adrenergic fibers and identify the proximal to distal gradient in diabetic neuropathy. The high interclass correlation coefficients between reviewers confirm that our results are reproducible.
107
Keywords: spinal cord injury, hypertension, plasticity, pain, blood pressure Financial support: Heart and Stroke Foundation of BC and the Yukon (of Canada).
Keywords: Pilomotor, neuropathy, sympathetic, adrenergic, diabetes doi:10.1016/j.autneu.2011.05.187 Financial support: NIH K23NS050209. P.173 Transient changes in BDNF parallel plasticity observed in the IML following distal axon injury doi:10.1016/j.autneu.2011.05.186 A.P. Coulibaly, B.F. Walsh, L.G. Isaacson(Miami University - Zoology, United States) P.172 The role of capsaicin-sensitive sensory neurons in autonomic dysreflexia in the spinal cord injured-rat L.M. Ramer (University of British Columbia -International Collaboration on Repair Discoveries, Canada), A.P. van Stolk (UBC -ICORD, Canada), J.A. Inskip (Simon Fraser University -Biomedical Physiology and Kinesiology, Canada), M.S. Ramer (University of British Columbia International Collaboration on Repair Discoveries, Canada), A.V. Krassioukov (University of British Columbia -Physical Medicine and Rehabilitation, Canada) Background: A subpopulation of sensory neurons express the transient receptor potential cation channel subfamily V member 1 (TRPV1). It is activated by heat (>43 °C), low pH, and capsaicin (the pungent ingredient in hot chili peppers), and has emerged as a promising target for the treatment of pain. Both pain and autonomic dysreflexia that develop in the wake of SCI have been attributed to maladaptive sensory plasticity. We hypothesize that TRPV-1-positive afferents contribute to the development of autonomic dysreflexia (AD). Methods: Wistar rats (300 g) received a complete transection of the spinal cord at the third (T3) or tenth (T10) thoracic segment or sham injury (durotomy without SCI). After 1–12 weeks, dorsal root ganglia (DRGs) and spinal cords were harvested and analyzed immunohistochemically to examine soma size of TRPV1-positive afferents and density of their central projections. A subset of rats received vehicle or capsaicin via intrathecal injection at 28 days; at 30 days, the severity of AD was assessed in these animals, by recording intra-arterial blood pressure during colo-rectal distension (CRD). Results: TRPV-1-positive nociceptors exhibited hypertrophy after T3 SCI. Nociceptor hypertrophy only occurred in DRGs below the level of SCI, and was more pronounced after high thoracic (T3) SCI. Hypertrophy was pronounced in DRGs far distal to SCI, and occurred in DRGs that contained both somatic (L4,L5) and visceral (L6,S1) afferents. TRPV-1-expressing nociceptors also appeared to sprout within the lumbar dorsal horn: the area occupied by TRPV-1-positive axons was increased one month after SCI. CRD-evoked hypertension was less pronounced in rats treated with capsaicin than in vehicletreated animals. Conclusion: TRPV-1-expressing nociceptors respond to SCI by undergoing somal hypertrophy and expanding their central terminals in the lumbar dorsal horn. Selective elimination of the central projections of these nociceptors reduces the severity of AD in rats with SCI. We are now examining the intriguing possibility that spontaneous activity in these neurons may contribute to the development of AD after SCI.
The neurotrophic regulation of sympathetic preganglionic neurons located in the intermediolateral cell column (IML) is poorly understood. We previously reported transient changes in the adult IML following injury to the cervical sympathetic trunk (CST), the distal axons entering the superior cervical ganglion (SCG). At 1 week following CST transection, activated astrocytes and microglia and increased numbers of trkB immunoreactive (− ir) oligodendrocytes populated the IML at levels C8-T1. This glial plasticity was paralleled by a decrease in choline acetyltransferase (ChAT)-ir neurons. Though ChAT was lost, neurons were present and expressed the injury marker activating transcription factor (ATF)-3. At 3 weeks, glial activation was absent, ChAT-ir neurons showed recovery, and ATF3-ir neurons declined to 13% of IML neurons. The number and appearance of ChAT-ir neurons were similar to controls at 10 weeks following injury. The changes in trkB suggested a role for the neurotrophin brain derived neurotrophic factor (BDNF) during this period of plasticity and provided the basis for the present study where we used western blot analysis to investigate BDNF levels in the spinal cord at 1 week, 3 weeks, and 10 weeks following CST transection. At 1 week following injury, when glial cells respond and ChAT is decreased, the 24 kDa isoform showed a significant decrease in all cases and the 37 kDa isoform was decreased in 4 of the 5 cases examined. At 21 days, when gliosis has subsided and ChAT expression is recovering, the 37 kDa form was significantly increased. BDNF returned to control values at 10 weeks following injury. The transient changes in BDNF may play a role in the IML neuroplasticity observed following injury. The BDNF protein in the cord is likely produced locally since the transected axons do not reinnervate the SCG by 10 weeks and could not derive BDNF from their SCG target. Keywords: sympathetic preganglionic neuron, neurotrophin regulation, choline acetyltransferase, trkB Financial support: NIHNS051206 to LGI, Undergraduate Research grant to BFW.
doi:10.1016/j.autneu.2011.05.188
P.174 Spectral analysis of cardiovascular control after spinal cord injury in rats: Effect of time post-injury J.A. Inskip (Simon Fraser University/University of British Columbia Biomedical Physiology and Kinesiology/International Collaboration on Repair Discoveries, Canada), L.M. Ramer (University of British Columbia -International Collaboration on Repair Discoveries/Zoology, Canada), M.S. Ramer (University of British Columbia -International Collaboration on Repair Discoveries/Zoology, Canada), A.V. Krassiou-
108
Abstracts / Autonomic Neuroscience: Basic and Clinical 163 (2011) 1–133
kovc, V.E. Claydon (University of British Columbia -Department of Physical Medicine and Rehabilitation/International Collaboration on Repair Discoveries, Canada) Background/aims: Spinal cord injury (SCI) can disrupt autonomic pathways resulting in a range of cardiovascular dysfunctions. Spectral analyses of heart rate and blood pressure have been used to evaluate the integrity of these cardiovascular autonomic pathways; however, we do not know whether these spectral parameters vary with time post-injury. To assess this, we performed spectral analyses of cardiovascular parameters in rats with complete thoracic SCI at one and three months post-injury. Methods: High-(T3) or low-(T10) thoracic complete SCI were performed on male Wistar rats. One or three months post-injury (or in uninjured controls), we recorded continuous beat-to-beat blood pressure by carotid artery cannulation. Univariate autoregressive spectral analyses were performed on time-series extracted from beat-to-beat data. Very low frequency (VLF), low frequency (LF) and high frequency (HF) peaks were identified and percentage power was calculated. Results: Systolic arterial pressure (SAP) variability was altered by high-thoracic SCI: LF power was reduced one and three months postinjury compared to controls (both p < 0.05); HF power was increased at one and three months (both p < 0.05); VLF power decreased at one month, returning to control levels by three months. Pulse interval variability was also affected by high-thoracic SCI: compared to controls, VLF power was reduced one and three months post-injury (p < 0.05); the LF power was reduced at one, but not three, months post-injury; HF power was increased at one and three months (both p < 0.05). Animals with low-thoracic SCI exhibited no changes in percentage power of VLF, LF or HF components of SAP or pulse interval variability one or three months post-injury. Conclusion: These results show that the abnormal cardiovascular neural regulation seen after complete high-thoracic SCI is stable between one and three months post-injury. Changes in VLF SAP over time suggest that myogenic vascular changes may develop postinjury. As expected, low-thoracic SCI did not appreciably alter cardiovascular frequency components. Keywords: spinal cord injury, cardiovascular function, autonomic pathways, spectral analysis, animal model Financial support: This work was supported by funding from Simon Fraser University and the Heart and Stroke Foundation.
doi:10.1016/j.autneu.2011.05.189
Sports, Canada), A.V. Krassioukov (University of British Columbia Physical Medicine and Rehabilitation, Canada) Introduction: Heart rate variability (HRV) describes the cyclic changes of the heart period (R–R interval) over time. Analysis of HRV in the frequency domain delineates parasympathetic from sympathetic components of the ANS, and may also provide information about baroreflex function. High frequency (HF) components (0.15 to 0.4 Hz) are an index of parasympathetic neural activity. Low frequency (LF) components (0.04 to 0.15 Hz) are an index of sympathetic neural activity. We examined changes in HRV as well as symptoms of orthostatic hypotension (OH) during an orthostatic challenge in tetraplegic rugby players to examine changes in autonomic function and symptoms of OH in persons with cervical complete (CC) and cervical incomplete (CI) SCI. Objective: Establish baseline cardiovascular parameters and prevalence of symptoms of orthostatic hypotension. Design: Prospective, cross-sectional study looking at prevalence/ manifestation of orthostatic hypotension among elite wheelchair athletes with SCI. Participants/methods: Continuous systolic and diastolic blood pressure and heart rate were recorded at rest and during a passive sit-up orthostatic test. All athletes were members of international rugby teams. Athletes also complete questionnaires about their experience of symptoms of OH everyday, during training, and during competition. Results: Data were examined from 10 CI SCI and 8 CC during international wheelchair rugby competition. At the time of testing, average age was 32 years and average time since injury was 13 years. Findings reveal that there are significant differences in autonomic function (LF and HF) both at rest and following an orthostatic challenge between CC and CI. At supine rest, CC had significantly greater LF than CI (964.9 ± 392.8 vs. 398.4 ± 212.2 ms2, respectively), and also greater HF (848.0 ± 470.7 vs. 294.6 ± 110.9 ms2). Following assumption of the upright posture, CC had significantly greater HF than CI (866.8 ± 324.4 vs. 304 ± 88.5 ms2) while there was no significant difference in LF. In response to the questionnaires, it is still unclear whether there are significant differences in the experience of symptoms of orthostatic hypotension between these individuals. Conclusion: Observations suggest that despite continuous training, hypotension and orthostatic hypotension are still common. However, there are differences in autonomic function and control between individuals with cervical complete and incomplete SCI as evidenced by differences in heart rate variability. Whether or not symptoms of orthostatic hypotension relate at all to autonomic completeness is still unknown.
P.175 Autonomic function and symptoms of orthostatic hypotension in wheelchair athletes
Keywords: spinal cord injury, autonomic function, heart rate variability, symptoms of orthostatic hypotension
S.C. Wong (University of British Columbia -Experimental Medicine, Canada), P. Mills (University of British Columbia -Physical Medicine and Rehabilitation, Canada), A. Tawashy (University of British Columbia -Rehabilitation Sciences, Canada), D. Mikhail (University of Western Ontario -Schulich School of Medicine and Dentistry, Canada), R. O'Connor (University of British Columbia -Medicine, Canada), D.E.R. Warburton (University of British Columbia -Experimental Medicine, Canada), J. Taunton (University of British Columbia Medicine, Canada), J. Eng (University of British Columbia -Rehabilitation Sciences, Canada), D. Campbell (BC Wheelchair Sports -BC Wheelchair
Financial support: International Paralympic Committee, Christopher and Dana Reeve Foundation, the Disability Research Network, the Michael Smith Foundation for Health Research, the Canadian Institutes of Health Research, and the International Collaboration on Repair Discoveries.
doi:10.1016/j.autneu.2011.05.190
Neurology 2010), expand the technique to light microscopy, use TH and DβH to stain for adrenergic fibers and identify the proximal to distal gradient in diabetic neuropathy. The high interclass correlation coefficients between reviewers confirm that our results are reproducible.
107
Keywords: spinal cord injury, hypertension, plasticity, pain, blood pressure Financial support: Heart and Stroke Foundation of BC and the Yukon (of Canada).
Keywords: Pilomotor, neuropathy, sympathetic, adrenergic, diabetes doi:10.1016/j.autneu.2011.05.187 Financial support: NIH K23NS050209. P.173 Transient changes in BDNF parallel plasticity observed in the IML following distal axon injury doi:10.1016/j.autneu.2011.05.186 A.P. Coulibaly, B.F. Walsh, L.G. Isaacson(Miami University - Zoology, United States) P.172 The role of capsaicin-sensitive sensory neurons in autonomic dysreflexia in the spinal cord injured-rat L.M. Ramer (University of British Columbia -International Collaboration on Repair Discoveries, Canada), A.P. van Stolk (UBC -ICORD, Canada), J.A. Inskip (Simon Fraser University -Biomedical Physiology and Kinesiology, Canada), M.S. Ramer (University of British Columbia International Collaboration on Repair Discoveries, Canada), A.V. Krassioukov (University of British Columbia -Physical Medicine and Rehabilitation, Canada) Background: A subpopulation of sensory neurons express the transient receptor potential cation channel subfamily V member 1 (TRPV1). It is activated by heat (>43 °C), low pH, and capsaicin (the pungent ingredient in hot chili peppers), and has emerged as a promising target for the treatment of pain. Both pain and autonomic dysreflexia that develop in the wake of SCI have been attributed to maladaptive sensory plasticity. We hypothesize that TRPV-1-positive afferents contribute to the development of autonomic dysreflexia (AD). Methods: Wistar rats (300 g) received a complete transection of the spinal cord at the third (T3) or tenth (T10) thoracic segment or sham injury (durotomy without SCI). After 1–12 weeks, dorsal root ganglia (DRGs) and spinal cords were harvested and analyzed immunohistochemically to examine soma size of TRPV1-positive afferents and density of their central projections. A subset of rats received vehicle or capsaicin via intrathecal injection at 28 days; at 30 days, the severity of AD was assessed in these animals, by recording intra-arterial blood pressure during colo-rectal distension (CRD). Results: TRPV-1-positive nociceptors exhibited hypertrophy after T3 SCI. Nociceptor hypertrophy only occurred in DRGs below the level of SCI, and was more pronounced after high thoracic (T3) SCI. Hypertrophy was pronounced in DRGs far distal to SCI, and occurred in DRGs that contained both somatic (L4,L5) and visceral (L6,S1) afferents. TRPV-1-expressing nociceptors also appeared to sprout within the lumbar dorsal horn: the area occupied by TRPV-1-positive axons was increased one month after SCI. CRD-evoked hypertension was less pronounced in rats treated with capsaicin than in vehicletreated animals. Conclusion: TRPV-1-expressing nociceptors respond to SCI by undergoing somal hypertrophy and expanding their central terminals in the lumbar dorsal horn. Selective elimination of the central projections of these nociceptors reduces the severity of AD in rats with SCI. We are now examining the intriguing possibility that spontaneous activity in these neurons may contribute to the development of AD after SCI.
The neurotrophic regulation of sympathetic preganglionic neurons located in the intermediolateral cell column (IML) is poorly understood. We previously reported transient changes in the adult IML following injury to the cervical sympathetic trunk (CST), the distal axons entering the superior cervical ganglion (SCG). At 1 week following CST transection, activated astrocytes and microglia and increased numbers of trkB immunoreactive (− ir) oligodendrocytes populated the IML at levels C8-T1. This glial plasticity was paralleled by a decrease in choline acetyltransferase (ChAT)-ir neurons. Though ChAT was lost, neurons were present and expressed the injury marker activating transcription factor (ATF)-3. At 3 weeks, glial activation was absent, ChAT-ir neurons showed recovery, and ATF3-ir neurons declined to 13% of IML neurons. The number and appearance of ChAT-ir neurons were similar to controls at 10 weeks following injury. The changes in trkB suggested a role for the neurotrophin brain derived neurotrophic factor (BDNF) during this period of plasticity and provided the basis for the present study where we used western blot analysis to investigate BDNF levels in the spinal cord at 1 week, 3 weeks, and 10 weeks following CST transection. At 1 week following injury, when glial cells respond and ChAT is decreased, the 24 kDa isoform showed a significant decrease in all cases and the 37 kDa isoform was decreased in 4 of the 5 cases examined. At 21 days, when gliosis has subsided and ChAT expression is recovering, the 37 kDa form was significantly increased. BDNF returned to control values at 10 weeks following injury. The transient changes in BDNF may play a role in the IML neuroplasticity observed following injury. The BDNF protein in the cord is likely produced locally since the transected axons do not reinnervate the SCG by 10 weeks and could not derive BDNF from their SCG target. Keywords: sympathetic preganglionic neuron, neurotrophin regulation, choline acetyltransferase, trkB Financial support: NIHNS051206 to LGI, Undergraduate Research grant to BFW.
doi:10.1016/j.autneu.2011.05.188
P.174 Spectral analysis of cardiovascular control after spinal cord injury in rats: Effect of time post-injury J.A. Inskip (Simon Fraser University/University of British Columbia Biomedical Physiology and Kinesiology/International Collaboration on Repair Discoveries, Canada), L.M. Ramer (University of British Columbia -International Collaboration on Repair Discoveries/Zoology, Canada), M.S. Ramer (University of British Columbia -International Collaboration on Repair Discoveries/Zoology, Canada), A.V. Krassiou-
108
Abstracts / Autonomic Neuroscience: Basic and Clinical 163 (2011) 1–133
kovc, V.E. Claydon (University of British Columbia -Department of Physical Medicine and Rehabilitation/International Collaboration on Repair Discoveries, Canada) Background/aims: Spinal cord injury (SCI) can disrupt autonomic pathways resulting in a range of cardiovascular dysfunctions. Spectral analyses of heart rate and blood pressure have been used to evaluate the integrity of these cardiovascular autonomic pathways; however, we do not know whether these spectral parameters vary with time post-injury. To assess this, we performed spectral analyses of cardiovascular parameters in rats with complete thoracic SCI at one and three months post-injury. Methods: High-(T3) or low-(T10) thoracic complete SCI were performed on male Wistar rats. One or three months post-injury (or in uninjured controls), we recorded continuous beat-to-beat blood pressure by carotid artery cannulation. Univariate autoregressive spectral analyses were performed on time-series extracted from beat-to-beat data. Very low frequency (VLF), low frequency (LF) and high frequency (HF) peaks were identified and percentage power was calculated. Results: Systolic arterial pressure (SAP) variability was altered by high-thoracic SCI: LF power was reduced one and three months postinjury compared to controls (both p < 0.05); HF power was increased at one and three months (both p < 0.05); VLF power decreased at one month, returning to control levels by three months. Pulse interval variability was also affected by high-thoracic SCI: compared to controls, VLF power was reduced one and three months post-injury (p < 0.05); the LF power was reduced at one, but not three, months post-injury; HF power was increased at one and three months (both p < 0.05). Animals with low-thoracic SCI exhibited no changes in percentage power of VLF, LF or HF components of SAP or pulse interval variability one or three months post-injury. Conclusion: These results show that the abnormal cardiovascular neural regulation seen after complete high-thoracic SCI is stable between one and three months post-injury. Changes in VLF SAP over time suggest that myogenic vascular changes may develop postinjury. As expected, low-thoracic SCI did not appreciably alter cardiovascular frequency components. Keywords: spinal cord injury, cardiovascular function, autonomic pathways, spectral analysis, animal model Financial support: This work was supported by funding from Simon Fraser University and the Heart and Stroke Foundation.
doi:10.1016/j.autneu.2011.05.189
Sports, Canada), A.V. Krassioukov (University of British Columbia Physical Medicine and Rehabilitation, Canada) Introduction: Heart rate variability (HRV) describes the cyclic changes of the heart period (R–R interval) over time. Analysis of HRV in the frequency domain delineates parasympathetic from sympathetic components of the ANS, and may also provide information about baroreflex function. High frequency (HF) components (0.15 to 0.4 Hz) are an index of parasympathetic neural activity. Low frequency (LF) components (0.04 to 0.15 Hz) are an index of sympathetic neural activity. We examined changes in HRV as well as symptoms of orthostatic hypotension (OH) during an orthostatic challenge in tetraplegic rugby players to examine changes in autonomic function and symptoms of OH in persons with cervical complete (CC) and cervical incomplete (CI) SCI. Objective: Establish baseline cardiovascular parameters and prevalence of symptoms of orthostatic hypotension. Design: Prospective, cross-sectional study looking at prevalence/ manifestation of orthostatic hypotension among elite wheelchair athletes with SCI. Participants/methods: Continuous systolic and diastolic blood pressure and heart rate were recorded at rest and during a passive sit-up orthostatic test. All athletes were members of international rugby teams. Athletes also complete questionnaires about their experience of symptoms of OH everyday, during training, and during competition. Results: Data were examined from 10 CI SCI and 8 CC during international wheelchair rugby competition. At the time of testing, average age was 32 years and average time since injury was 13 years. Findings reveal that there are significant differences in autonomic function (LF and HF) both at rest and following an orthostatic challenge between CC and CI. At supine rest, CC had significantly greater LF than CI (964.9 ± 392.8 vs. 398.4 ± 212.2 ms2, respectively), and also greater HF (848.0 ± 470.7 vs. 294.6 ± 110.9 ms2). Following assumption of the upright posture, CC had significantly greater HF than CI (866.8 ± 324.4 vs. 304 ± 88.5 ms2) while there was no significant difference in LF. In response to the questionnaires, it is still unclear whether there are significant differences in the experience of symptoms of orthostatic hypotension between these individuals. Conclusion: Observations suggest that despite continuous training, hypotension and orthostatic hypotension are still common. However, there are differences in autonomic function and control between individuals with cervical complete and incomplete SCI as evidenced by differences in heart rate variability. Whether or not symptoms of orthostatic hypotension relate at all to autonomic completeness is still unknown.
P.175 Autonomic function and symptoms of orthostatic hypotension in wheelchair athletes
Keywords: spinal cord injury, autonomic function, heart rate variability, symptoms of orthostatic hypotension
S.C. Wong (University of British Columbia -Experimental Medicine, Canada), P. Mills (University of British Columbia -Physical Medicine and Rehabilitation, Canada), A. Tawashy (University of British Columbia -Rehabilitation Sciences, Canada), D. Mikhail (University of Western Ontario -Schulich School of Medicine and Dentistry, Canada), R. O'Connor (University of British Columbia -Medicine, Canada), D.E.R. Warburton (University of British Columbia -Experimental Medicine, Canada), J. Taunton (University of British Columbia Medicine, Canada), J. Eng (University of British Columbia -Rehabilitation Sciences, Canada), D. Campbell (BC Wheelchair Sports -BC Wheelchair
Financial support: International Paralympic Committee, Christopher and Dana Reeve Foundation, the Disability Research Network, the Michael Smith Foundation for Health Research, the Canadian Institutes of Health Research, and the International Collaboration on Repair Discoveries.
doi:10.1016/j.autneu.2011.05.190