Age-related change in the effect of gentle mechanical cutaneous stimulation on the somato-cardiac sympathetic C-reflex

Abstract

This study examined whether aging influences the effect of gentle mechanical cutaneous stimulation (touch) on somato-cardiac sympathetic reflexes in anesthetized rats. A single electrical stimulus (15 V, 0.5 ms) applied to the tibial nerve induced somato-cardiac sympathetic A- and C-reflexes, which originated from the myelinated A- and unmyelinated C-fibers of the tibial nerve, respectively. When touch was applied to the inner thigh ipsilateral to the electrical stimulation, the C-reflex was selectively inhibited in adult rats (4-12 months), and this response was abolished by the opioid receptor antagonist, naloxone. Such an inhibitory effect of touch was impaired in aged rats (26-30 months). In contrast, depression of both A- and C-reflexes during a phenylephrine-induced rise in blood pressure was well maintained in the aged group. This study indicates that activation of the opioidergic system by gentle mechanical cutaneous stimulation attenuates with aging.

Types of Skin Afferent Fibers and Spinal Opioid Receptors that Contribute to Touch-Induced Inhibition of Heart Rate Changes Evoked by Noxious Cutaneous Heat Stimulation

“…In addition, according to Gibbs et al [ 27 ], the frequency of bradycardiac and depressor response increases when the concentration of inhalation anesthetics becomes higher. Thus, it was assumed that bradycardiac responses were more likely to be caused due to experimental conditions in the present study (noxious heat stimulation applied to the lower back and rumps and deeper anesthesia than conventional depth [ 8 , 9 ]). A difference in cardiovascular responses to noxious stimulation (bradycardia or tachycardia) was assumed to be centrally mediated [ 27 ].…”

“…The preparatory surgery was described previously [ 8 , 9 ]. In brief, the carotid artery and jugular vein were catheterized for continuous arterial blood pressure recording and administration of anesthetics and supplemental fluids, respectively.…”

“…Recently, we have found that somatoautonomic reflexes are inhibited by gently touching the skin in anesthetized rats [ 8 , 9 ] and conscious humans [ 10 ]. In these studies, the effect of touch using a soft disc filled with microcones, which array regularly with a constant pitch (a recently created device for continuously applying touch effect with a fingertip), was compared with that using a disc without microcones (i.e., a flat surface).…”

“…A comparison of the human brain activity (glucose metabolism) during these two types of touch using positron emission tomography revealed no difference in the somatosensory cortex [ 11 ]. In anesthetized rats, the somatocardiac sympathetic reflex evoked by the activation of tibial C afferent fibers (the C-reflex) was selectively inhibited by microcone touch applied to the thigh [ 8 , 9 ]. This inhibitory effect on the C-reflex gradually appeared following the onset of continuous touch and slowly disappeared after termination of the touch.…”

Gentle Perineal Skin Stimulation for Control of Nocturia

“…Natural stimulation such as gentle touch is able to activate these non-noxious nerve fibers without noxious fiber activation. While little is known about the physiological functions of low-threshold mechanoreceptive Aδ and C fibers, we found that these afferents may contribute to autonomic regulation (Hotta et al, 2010(Hotta et al, , 2018Watanabe et al, 2011Watanabe et al, , 2015. In the following section, the effects of natural stimulation (gentle stimulation) on urinary bladder function are introduced.…”