Pressor reflex evoked by muscular contraction: contributions by neuraxis levels

Iwamoto, Gary A.; Waldrop, Tony G.; Kaufman, Marc P.; Botterman, B. R.; Rybicki, K. J.; Mitchell, Jere H.

doi:10.1152/jappl.1985.59.2.459

Cited by 78 publications

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“…piratory responses are mediated in part by central motor commands and in part by the "exercise pressor reflex," which originates in small-diameter group III and IV (A␦ and C) afferents from active muscles (Iwamoto et al 1985;Mitchell and Schmidt 1983;Wilson and Hand 1997). These receptors are either directly excited by contraction (mechanosensitive) or indirectly excited by metabolites released from the contracting muscle (metabo-receptive; Kaufman and Forster 1996;Kaufman et al 1983;Kniffki et al 1981;McCloskey and Mitchell 1972).…”

Section: Discussionmentioning

confidence: 99%

“…The brain stem plays a pivotal role in homeostatic responses, including cardiovascular and respiratory responses to muscle work (Iwamoto et al 1985). Static contraction of skeletal muscle activates small-diameter afferents that evoke a reflex increase in sympathetic nerve activity and cardiovascular function (Kaufman and Forster 1996;Mitchell and Schmidt 1983;Wilson and Hand 1997).…”

Section: Introductionmentioning

confidence: 99%

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Activation of Spinobulbar Lamina I Neurons by Static Muscle Contraction

Wilson

Andrew

Craig

2002

Journal of Neurophysiology

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. Activation of spinobulbar lamina I neurons by static muscle contraction. J Neurophysiol 87: 1641-1645, 2002; 10.1152/jn.00609.2001. Spinal lamina I neurons are selectively activated by small-diameter somatic afferents, and they project to brain stem sites that are critical for homeostatic control. Because small-diameter afferent activity evoked by contraction of skeletal muscle reflexly elicits exercise-related cardiorespiratory activation, we tested whether spinobulbar lamina I cells respond to muscle contraction. Spinobulbar lamina I neurons were identified in chloralose-anesthetized cats by antidromic activation from the ipsilateral caudal ventrolateral medulla. Static contractions of the ipsilateral triceps surae muscle were evoked by tibial nerve stimulation using parameters that avoid afferent activation, and arterial blood pressure responses were recorded. Recordings were maintained from 13 of 17 L 7 lamina I spinobulbar neurons during static muscle contraction, and 5 of these neurons were excited. Three were selectively activated only by muscle afferents and did not have a cutaneous receptive field. Spinobulbar lamina I neurons activated by muscle contraction provide an ascending link for the reflex cardiorespiratory adjustments that accompany muscular work. This study provides an important first step in elucidating an ascending afferent pathway for somato-autonomic reflexes.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Activation of Spinobulbar Lamina I Neurons by Static Muscle Contraction

Wilson

Andrew

Craig

2002

Journal of Neurophysiology

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“…In hypertension, combined or individual activation of either the mechanical (i.e., mechanoreflex) or metabolic component (i.e., metaboreflex) of the EPR results in a heightened sympathetically mediated cardiovascular response (2,13,22,23,34,38). To date, however, the mechanisms underlying EPR overactivity in hypertension remain largely unknown.The nucleus tractus solitarius (NTS) within the medulla oblongata of the brainstem is a central site of integration for sensory information from skeletal muscle afferents fibers (7,26,42). As evidence, anterograde tracing with biotinylated dextran amine of ascending neuronal projections from the spinal cord, to which skeletal muscle afferents contribute, has demonstrated that these fibers project to the NTS (30).…”

mentioning

confidence: 99%

“…The nucleus tractus solitarius (NTS) within the medulla oblongata of the brainstem is a central site of integration for sensory information from skeletal muscle afferents fibers (7,26,42). As evidence, anterograde tracing with biotinylated dextran amine of ascending neuronal projections from the spinal cord, to which skeletal muscle afferents contribute, has demonstrated that these fibers project to the NTS (30).…”

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confidence: 99%

Neuronal nitric oxide synthase expression is lower in areas of the nucleus tractus solitarius excited by skeletal muscle reflexes in hypertensive rats

Murphy

Mizuno²,

Downey

et al. 2013

American Journal of Physiology-Heart and Circulatory Physiology

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Murphy MN, Mizuno M, Downey RM, Squiers JJ, Squiers KE, Smith SA. Neuronal nitric oxide synthase expression is lower in areas of the nucleus tractus solitarius excited by skeletal muscle reflexes in hypertensive rats. Am J Physiol Heart Circ Physiol 304: H1547-H1557, 2013. First published April 5, 2013; doi:10.1152/ajpheart.00235.2012.-The functions of the skeletal muscle exercise pressor reflex (EPR) and its mechanically sensitive component are augmented in hypertension producing exaggerated increases in blood pressure during exercise. Afferent information from the EPR is processed in the nucleus tractus solitarius (NTS). Within the NT, nitric oxide (NO), produced via L-arginine oxidation by neuronal nitric oxide synthase (nNOS), buffers the pressor response to EPR activation. Therefore, EPR overactivity may manifest as a decrease in NO production due to reductions in nNOS. We hypothesized that nNOS protein expression is lower in the NTS of spontaneously hypertensive (SHR) compared with normotensive Wistar-Kyoto (WKY) rats. Further, we examined whether nNOS is expressed with FOS, a marker of neuronal excitation induced by EPR activation. The EPR and mechanoreflex were intermittently activated for 1 h via hindlimb static contraction or stretch, respectively. These maneuvers produced significantly greater pressor responses in SHR during the first 25 min of stimulation. Within the NTS, nNOS expression was lower from Ϫ14.9 to Ϫ13.4 bregma in SHR compared with WKY. For example, at Ϫ14.5 bregma the number of NTS nNOS-positive cells in SHR (13 Ϯ 1) was significantly less than WKY (23 Ϯ 2). However, the number of FOS-positive cells after muscle contraction in this area was not different (WKY ϭ 82 Ϯ 18; SHR ϭ 75 Ϯ 8). In both groups, FOS-expressing neurons were located within the same areas of the NTS as neurons containing nNOS. These findings demonstrate that nNOS protein expression is lower within NTS areas excited by skeletal muscle reflexes in hypertensive rats.hypertension; exercise; nucleus tractus solitarius PHYSICAL ACTIVITY INDUCES increases in arterial blood pressure (ABP), heart rate (HR), and sympathetic nerve activity (20,32). In hypertension, exercise evokes abnormally exaggerated elevations in each of these variables (2, 9, 27). This places hypertensive patients at a greater risk for the occurrence of an adverse cardiovascular and/or cerebrovascular event during or immediately after a bout of exercise (6, 21). As a result, the intensity and duration of exercise prescription at a level that is both safe and therapeutically effective are often limited. Thus determining the cause of the cardiovascular hyperexcitability manifest in hypertension is clinically important.Exercise-induced autonomic changes in the cardiovascular system are mediated by the central command, the arterial baroreflex and the exercise pressor reflex (EPR; Refs. 4,18,19). Of these, recent evidence in both the animal and human literature suggests that the EPR contributes significantly to the abnormally accentuated circulatory response to ...

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“…1). Cats decerebrated at the midcollicular level reportedly exhibited a larger pressor response to continuous contraction of hindlimb skeletal muscle than cats decerebrated at 5-mm rostral to the obex 27) . Moreover, C1 spinal transection abolished the EPR response.…”

Section: Exercise Pressor Reflex Arcmentioning

confidence: 84%

Exercise pressor reflex in health and diseases: Animal studies

Koba

2015

JPFSM

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A reflex originating in exercising skeletal muscle contributes to sympathoexcitation during exercise. This muscle-based reflex is termed the exercise pressor reflex (EPR). In this review, mechanisms underlying activation of the EPR are examined based on findings mainly obtained from cat studies. Specifically, roles played by chemical and mechanical stimuli due to contraction in increasing discharges of muscle afferent fibers are discussed. Roles metabolic byproducts play in stimulating and sensitizing muscle afferents are also examined. Central cardiovascular sites involved in activation of the EPR are investigated. In this review, moreover, mechanisms by which the EPR function becomes abnormal in heart failure and hypertension are discussed on the basis of experimental data mainly provided by rat studies. In heart failure, the muscle metaboreflex is attenuated while the mechanoreflex is enhanced. In hypertension, both the muscle metabo-and mechano-reflexes are enhanced. Peripheral factors leading to EPR dysfunction in these pathological conditions are examined.

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Pressor reflex evoked by muscular contraction: contributions by neuraxis levels

Cited by 78 publications

References 0 publications

Activation of Spinobulbar Lamina I Neurons by Static Muscle Contraction

Activation of Spinobulbar Lamina I Neurons by Static Muscle Contraction

Neuronal nitric oxide synthase expression is lower in areas of the nucleus tractus solitarius excited by skeletal muscle reflexes in hypertensive rats

Exercise pressor reflex in health and diseases: Animal studies

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