Heart Rate Changes in Response to Mechanical Pressure Stimulation of Skeletal Muscles Are Mediated by Cardiac Sympathetic Nerve Activity

Abstract

Stimulation of mechanoreceptors in skeletal muscles such as contraction and stretch elicits reflexive autonomic nervous system changes which impact cardiovascular control. There are pressure-sensitive mechanoreceptors in skeletal muscles. Mechanical pressure stimulation of skeletal muscles can induce reflex changes in heart rate (HR) and blood pressure, although the neural mechanisms underlying this effect are unclear. We examined the contribution of cardiac autonomic nerves to HR responses induced by mechanical pressure stimulation (30 s, ~10 N/cm2) of calf muscles in isoflurane-anesthetized rats. Animals were artificially ventilated and kept warm using a heating pad and lamp, and respiration and core body temperature were maintained within physiological ranges. Mechanical stimulation was applied using a stimulation probe 6 mm in diameter with a flat surface. Cardiac sympathetic and vagus nerves were blocked to test the contribution of the autonomic nerves. For sympathetic nerve block, bilateral stellate ganglia, and cervical sympathetic nerves were surgically sectioned, and for vagus nerve block, the nerve was bilaterally severed. In addition, mass discharges of cardiac sympathetic efferent nerve were electrophysiologically recorded. Mechanical stimulation increased or decreased HR in autonomic nerve-intact rats (range: −56 to +10 bpm), and the responses were negatively correlated with pre-stimulus HR (r = −0.65, p = 0.001). Stimulation-induced HR responses were markedly attenuated by blocking the cardiac sympathetic nerve (range: −9 to +3 bpm, p < 0.0001) but not the vagus nerve (range: −75 to +30 bpm, p = 0.17). In the experiments with cardiac sympathetic efferent nerve activity recordings, mechanical stimulation increased, or decreased the frequency of sympathetic nerve activity in parallel with HR (r = 0.77, p = 0.0004). Furthermore, the changes in sympathetic nerve activity were negatively correlated with its tonic level (r = −0.62, p = 0.0066). These results suggest that cardiac sympathetic nerve activity regulates HR responses to muscle mechanical pressure stimulation and the direction of HR responses depends on the tonic level of the nerve activity, i.e., bradycardia occurs when the tonic activity is high and tachycardia occurs when the activity is low.

Interpersonal touch interventions for patients in intensive care: A design‐oriented realist review

“…This interpretation, however, remains tentative due to the small number of studies employing a sedation condition, differences in outcome measures employed and potentially confounding variables such as intervention design and the degree of pressure employed. Both sedation condition studies employed gentle massage techniques, whereas the majority of restricted sedation studies demonstrating stronger evidence for effects used greater pressure in the form of acupressure or reflexology, which may elicit more direct autonomic effects (Field, ; Watanabe & Hotta, ; Section ).…”

“…In the light of evidence that cortical processing may be a key mechanism underlying the benefits of gentle, medium‐velocity touch (Table , Figure b), gentle touch may have limited effectiveness for sedated patients due to reduced corticocortical and subcorticocortical connectivity (MacDonald, Naci, MacDonald, & Owen, ). In contrast, moderate pressure touch is suggested to elicit a relaxation response by increasing parasympathetic activity and/or reducing sympathetic activity (Field, ; Watanabe & Hotta, ). The mechanisms underlying the effects of moderate pressure touch may therefore be less reliant on cortical processes (Table ; Construction Principle 6).…”

The Impact of Stretching Intensities on Neural and Autonomic Responses: Implications for Relaxation

“…Research has reported that static stretching increases heart rate and blood pressure [ 29 , 30 ]. Underlying mechanisms have been linked to muscle sympathetic nerve activity, cardiac sympathetic nerve activity, and vagal withdrawal [ 31 , 32 , 33 ]. In our study, sympathetic nervous activity increased during the resting phases after stretching, which deviates from some previous findings.…”

The Relationship between Autonomic Regulation of Cardiovascular Function and Body Composition

“…Mechanical pressure stimulation of skeletal muscles can induce reflex changes in HR and BP, although the neural mechanisms underlying this effect are unclear. 28 A recently published study showed that cardiac sympathetic nerve activity regulates HR responses to muscle mechanical pressure stimulation and that the direction of HR responses depends on the tonic level of the nerve activity, i.e., bradycardia occurs when the tonic activity is high, and tachycardia occurs when the activity is low. 28 On the other hand, we found no correlation between the VR and anthropometric measurements, which are more specific markers of obesity.…”