Identification of the spinal pathways involved in the recovery of baroreflex control after spinal lesion in the rat using pseudorabies virus

Castillo, Deborah G.; Zahner, Matthew R.; Schramm, Lawrence P.

doi:10.1152/ajpregu.00008.2012

Cited by 4 publications

(7 citation statements)

References 35 publications

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“…We performed spinal lesion on rats at an appropriate age such that baroreflex tests would be performed, after a 1-week or 7-week recovery period, on early adult (∼12-week-old) rats. This age of rat correlates to a 24-year-old human ( Sengupta, 2013 ) and was based on our previous studies in the rat ( Pan et al, 2005 ; Mountney et al, 2010 , 2013 ; Zahner et al, 2011 ; Castillo et al, 2012 ). 14 rats died due to spinal cord surgery or during the acute renal sympathetic nerve recordings.…”

Section: Methodsmentioning

confidence: 92%

“…While EODF has been shown to augment the recovery of motor and sensory function after SCI ( Plunet et al, 2008 , 2010 ; Jeong et al, 2011 ), data on the extent of recovery of sympathetic cardiovascular regulation are limited. Based on studies from our laboratory to show recovery of baroreflex control of sympathetic activity after chronic SCI ( Zahner and Schramm, 2011 ; Zahner et al, 2011 ; Castillo et al, 2012 ), as well as studies to suggest that caloric restriction augments baroreflex responsiveness in the naïve rat with intact spinal cords ( Herlihy et al, 1992 ; Thomas et al, 1993 ), it was our intent to determine if EODF also augments the recovery of baroreflex regulation of sympathetic activity after SCI. Even though others have shown that EODF augments the recovery of motor and sensory function, this study provides important new physiological evidence to show that chronic EODF does not improve the impaired baroreflex regulation ability to suppress sympathetic activity at elevated blood pressures in rats after SCI.…”

Section: Discussionmentioning

confidence: 99%

“…Serial horizontal sections of the spinal cord from T1 to T12 were cut with a freezing microtome (40 μm). After processing, sections were mounted on slides and examined microscopically to verify that the lesion completely transected the left hemisphere of the spinal cord while leaving the right hemisphere intact as previously reported ( Zahner et al, 2011 ; Castillo et al, 2012 ).…”

Section: Methodsmentioning

confidence: 99%

“…Acute recordings in EODF rats were performed after an ad-lib cycle and no rats were fasted 24hr prior to surgery. For acute baroreflex experiments, rats were initially anesthetized with isoflurane and prepared as previously described ( Mountney et al, 2010 ; Zahner and Schramm, 2011 ; Zahner et al, 2011 ; Castillo et al, 2012 ). Adequate depth of anesthesia was confirmed by the absence of a withdrawal response to a noxious stimulus (tail pinch).…”

Section: Methodsmentioning

confidence: 99%

“…We have previously shown that baroreflex regulation in spinally-lesioned rats improves over time and that the degree of recovery is dependent on the rostrocaudal location of the lesion ( Zahner et al, 2011 ). Also, using the transsynaptic tracer pseudorabies virus we have shown that partial improvement is likely due to increased efficiency of existing spinal pathways, as opposed to the formation of new spinal pathways to circumvent the lesion site ( Castillo et al, 2012 ).…”

Section: Introductionmentioning

confidence: 99%

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Intermittent Fasting After Spinal Cord Injury Does Not Improve the Recovery of Baroreflex Regulation in the Rat

Zahner

Beaumont

2020

Front. Physiol.

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Modest recovery of somatic function after incomplete spinal cord injury (SCI) has been widely demonstrated. Recently we have shown that spontaneous recovery of baroreflex regulation of sympathetic activity also occurs in rats. Dietary restriction in the form of every other day fasting (EODF) has been shown to have beneficial effects on the recovery of motor function after SCI in rats. The goal of this study was to determine if EODF augments the improvement of baroreflex regulation of sympathetic activity after chronic left thoracic (T 8 ) surgical spinal hemisection. To determine this, we performed baroreflex tests on ad-lib fed or EODF rats 1 week or 7 weeks after left T 8 spinal hemisection. One week after T 8 left hemisection baroreflex testing revealed that gain of baroreflex responsiveness, as well as the ability to increase renal sympathetic nerve activity (RSNA) at low arterial pressure, was significantly impaired in the ad-lib fed but not the EODF rats compared with sham lesioned control rats. However, baroreflex tests performed 7 weeks after T 8 left hemisection revealed the inability of both ad-lib and EODF rats to decrease RSNA at elevated arterial pressures. While there is evidence to suggest that EODF has beneficial effects on the recovery of motor function in rats, EODF did not significantly improve the recovery of baroreflex regulation of sympathetic activity.

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Section: Methodsmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Intermittent Fasting After Spinal Cord Injury Does Not Improve the Recovery of Baroreflex Regulation in the Rat

Zahner

Beaumont

2020

Front. Physiol.

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Sympathetic Preganglionic Neurons: Properties and Inputs

Deuchars

Lall

2015

Comprehensive Physiology

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The sympathetic nervous system comprises one half of the autonomic nervous system and participates in maintaining homeostasis and enabling organisms to respond in an appropriate manner to perturbations in their environment, either internal or external. The sympathetic preganglionic neurons (SPNs) lie within the spinal cord and their axons traverse the ventral horn to exit in ventral roots where they form synapses onto postganglionic neurons. Thus, these neurons are the last point at which the central nervous system can exert an effect to enable changes in sympathetic outflow. This review considers the degree of complexity of sympathetic control occurring at the level of the spinal cord. The morphology and targets of SPNs illustrate the diversity within this group, as do their diverse intrinsic properties which reveal some functional significance of these properties. SPNs show high degrees of coupled activity, mediated through gap junctions, that enables rapid and coordinated responses; these gap junctions contribute to the rhythmic activity so critical to sympathetic outflow. The main inputs onto SPNs are considered; these comprise afferent, descending, and interneuronal influences that themselves enable functionally appropriate changes in SPN activity. The complexity of inputs is further demonstrated by the plethora of receptors that mediate the different responses in SPNs; their origins and effects are plentiful and diverse. Together these different inputs and the intrinsic and coupled activity of SPNs result in the rhythmic nature of sympathetic outflow from the spinal cord, which has a variety of frequencies that can be altered in different conditions.

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Activation of nociception‐sensitive ionotropic glutamate receptor‐expressing rostroventrolateral medulla neurons by stimulation of cardiac afferents in rats

Zahner,

Oculam,

Beaumont

2024

FASEB BioAdvances

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Myocardial ischemia causes the release of bradykinin, which activates afferent nerve endings in the ventricular epicardium. This elicits a sympathetically mediated increase in arterial pressure and heart rate, referred to as the cardiogenic sympathetic afferent reflex. The rostroventrolateral medulla (RVLM) is a key sympathetic brain stem site for regulating cardiovascular activity. This study aimed to determine the importance of non‐barosensitive nociception sympathetic activity and the role of glutamate receptor activation of RVLM neurons in the cardiogenic sympathetic afferent reflex. We tested the hypothesis that inhibition of barosensitive sympathetic activity attenuates but does not abolish the reflex response to cardiac visceral afferents. Renal sympathetic nerve activity (RSNA), arterial pressure, and heart rate responses to epicardial bradykinin application were recorded in anesthetized rats before and after bilateral RVLM microinjection of either GABAA agonist muscimol, ionotropic glutamate receptor antagonist kynurenic acid, N‐methyl‐d‐aspartate (NMDA) receptor antagonist 2‐amino‐5‐ phosphonopentanoic acid (AP5), or non‐NMDA antagonist 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX). Baroreceptor loading‐induced inhibition of barosensitive activity attenuated the bradykinin‐induced RSNA response (93 ± 14% increase) and tachycardia (18 ± 3 bpm). While RVLM muscimol microinjection abolished the RSNA response (1.6 ± 4.2% from baseline, 0.49 ± 0.38 μV*s), surprisingly, it did not abolish the tachycardia (27 ± 4 bpm). Kynurenic acid microinjection blocked the arterial pressure and RSNA responses, while AP5 or CNQX only attenuated the responses. These data suggest that nociception‐sensitive sympathetic activity that does not appear to be barosensitive is also involved in the cardiogenic sympathetic afferent reflex. Importantly, while muscimol and kynurenic acid abolished the arterial pressure and RSNA response, neither affected the tachycardia, suggesting an alternate cardiac pathway independent of RVLM.

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Identification of the spinal pathways involved in the recovery of baroreflex control after spinal lesion in the rat using pseudorabies virus

Cited by 4 publications

References 35 publications

Intermittent Fasting After Spinal Cord Injury Does Not Improve the Recovery of Baroreflex Regulation in the Rat

Intermittent Fasting After Spinal Cord Injury Does Not Improve the Recovery of Baroreflex Regulation in the Rat

Sympathetic Preganglionic Neurons: Properties and Inputs

Activation of nociception‐sensitive ionotropic glutamate receptor‐expressing rostroventrolateral medulla neurons by stimulation of cardiac afferents in rats

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