Modulation of arterial baroreflex control of muscle sympathetic nerve activity by muscle metaboreflex in humans

Abstract

Ichinose, Masashi, Mitsuru Saito, Hiroyuki Wada, Asami Kitano, Narihiko Kondo, and Takeshi Nishiyasu. Modulation of arterial baroreflex control of muscle sympathetic nerve activity by muscle metaboreflex in humans. Am J Physiol Heart Circ Physiol 286: H701-H707, 2004; 10.1152/ajpheart.00618.2003.-We aimed to investigate the interaction [with respect to the regulation of muscle sympathetic nerve activity (MSNA) and blood pressure] between the arterial baroreflex and muscle metaboreflex in humans. In 10 healthy subjects who performed a 1-min sustained handgrip exercise at 50% maximal voluntary contraction followed by forearm occlusion, arterial baroreflex control of MSNA (burst incidence and strength and total activity) was evaluated by analyzing the relationship between beatby-beat spontaneous variations in diastolic arterial blood pressure (DAP) and MSNA both during supine rest (control) and during postexercise muscle ischemia (PEMI). During PEMI (vs. control), 1) the linear relationship between burst incidence and DAP was shifted rightward with no alteration in sensitivity, 2) the linear relationship between burst strength and DAP was shifted rightward and upward with no change in sensitivity, and 3) the linear relationship between total activity and DAP was shifted to a higher blood pressure and its sensitivity was increased. The modification of the control of total activity that occurs in PEMI could be a consequence of alterations in the baroreflex control of both MSNA burst incidence and burst strength. These results suggest that the arterial baroreflex and muscle metaboreflex interact to control both the occurrence and strength of MSNA bursts. skeletal muscle metaboreflex; arterial blood pressure; exercise STATIC AND DYNAMIC EXERCISE is accompanied by increases in arterial blood pressure, heart rate (HR), and sympathetic nerve activity (SNA). These cardiovascular responses are hypothesized to be mediated by a number of factors: 1) central command (24), 2) feedback mechanisms via the afferent nerves (group III and IV fibers) arising from the working skeletal muscles (16,17,23), and 3) arterial and cardiopulmonary baroreflexes (23,24). It has been hypothesized that during heavy exercise the arterial baroreflexes and muscle metaboreflexes are both activated and that they interact to regulate the responses shown by blood pressure, HR, and SNA levels (8-10, 18, 21, 22, 29, 31).Two types of interaction between arterial baroreflexes and muscle metaboreflexes in the control of cardiovascular responses have been demonstrated. The first involves arterial baroreflexes opposing the pressor response elicited via the muscle metaboreflexes (18,21,29,31). Evidence for this opposing effect of the arterial baroreflexes has been obtained during dynamic exercise in dogs (31) as well as during static handgrip exercise (29) and postexercise muscle ischemia (PEMI) in humans (18). The second type of interaction is a modulation of arterial baroreflex function during muscle metaboreflex activation (8-10, 22). Indeed, Papelier et al....

Augmented pressor and sympathetic responses to skeletal muscle metaboreflex activation in type 2 diabetes patients

“…Since previous work suggests that the sensitivity of the arterial baroreflex may be impaired in con- ditions associated with T2D such as obesity (6,16) and hypertension (17,31), we examined the interaction between the muscle metaboreflex and the arterial baroreflex. Our findings suggest that an impaired baroreflex control of MSNA does not appear to contribute to the augmented MSNA and BP responses observed during PEI since both groups exhibited an increase in MSNA baroreflex sensitivity with PEI, similar to previous studies (8,20,22). However, since only spontaneous baroreflex measures were used, additional studies are needed to more fully characterize arterial baroreflex function.…”

“…Indeed, studies have shown exaggerated neural cardiovascular responses when input from the arterial baroreflex is removed (48,56). Likewise, in healthy humans, an increase in the baroreflex control of MSNA has been observed during isolation of the muscle metaboreflex with PEI (8,20,22). Since previous work suggests that the sensitivity of the arterial baroreflex may be impaired in con- ditions associated with T2D such as obesity (6,16) and hypertension (17,31), we examined the interaction between the muscle metaboreflex and the arterial baroreflex.…”

Individual differences in the heart rate response to activation of the muscle metaboreflex in humans

“…Although we previously observed that the mean HR during PEMI did not differ from the resting HR in a group of subjects, we noted that in several subjects HR did increase or decrease from the resting levels during PEMI, suggesting that there are considerable individual differences in the HR response to PEMI (13)(14)(15)(16)(17)(27)(28)(29). To our knowledge, however, these individual differences have never been systematically investigated.…”

The Influence of the Call with a Mobile Phone on Heart Rate Variability Parameters in Healthy Volunteers

“…It was demonstrated that change in forearm position may have an impact on sympathetic nerves in muscles of hand 35) . However, reports are concentrated on forearm raise together with handgrip exercises performed more or less intensively, which could cause the increase in sympathetic activity 35,36) . For these reasons we think that results of our experiments were not ultimately interfered by holding a telephone.…”