Influence of Muscle Afferents on Cutaneous and Muscle Vessels in the Dog

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1 Influence of Muscle Afferents on Cutaneous and Muscle Vessels in the Dog By Denis L Clement and John T. Shepherd ABSTRACT In 13 anesthetized dogs with their vagi cut and their carotid sinuses kept at constant pressure, the gracilis artery, cranial tibial artery, and lateral saphenous vein of the left hind limb were isolated and perfused at constant flow. In the right hind limb, muscle afferents were stimulated by electrodes in the thigh muscles. At 5 Hz, aortic blood pressure decreased 45 ± 8 ; perfusion pressure decreased in the gracilis muscle and the paw (26 ± 6 and 26 ± 5, respectively) and increased in the saphenous vein (13 ± 3 ). These effects were not prevented by paralysis of the stimulated muscles, beta-receptor blockade, or administration of atropine or antihistaminic drugs. At 40 Hz, aortic blood pressure increased 29 ± 8 ; perfusion pressure increased in the gracilis muscle and the paw (33 ± 5 and 33 ± 3, respectively) and decreased in the saphenous vein (20 ± 2 ). These effects were prevented or reversed by paralysis of the stimulated muscles. Similar effects were obtained by central stimulation of the femoral nerve. Left sympathectomy or alpha-receptor blockade abolished the responses in the isolated vascular beds. Thus, muscle contraction is necessary only to activate the muscle afferents which cause constriction of resistance vessels in muscle and paw and dilation of cutaneous veins. KEY WORDS gracilis artery muscular exercise autonomic control muscle receptors cranial tibial artery atropine lateral saphenous vein muscle contraction sympathectomy alpha-receptor blockade A recent study (1) in the dog has shown that contraction of the muscles of the thigh can cause reflex changes in aortic blood pressure and vascular resistance in the hind limb. In this experiment, the changes in the perfusion pressure in the iliac artery were used to study the vascular responses in the hind limb. However, the iliac artery provides the blood supply to different vascular beds, and the responses in this artery might not always reflect the reaction of each of these beds. Opposite responses in the resistance vessels of muscle and paw have been reported during chemoreceptor stimulation (2). In the present study, the reactions of the resistance vessels in muscle and paw and of the cutaneous veins were compared during stimulation of somatic afferents from muscle. Methods PREPARATION Thirteen dogs (15-25 kg) were anesthetized with thiopental (15 mg/kg, iv) and chloralose (80 mg/kg, iv) From the Mayo Clinic and Mayo Foundation, Rochester, Minnesota This investigation was supported in part by U. S. Public Health Service Grant HL-5883 from the National Heart and Lung Institute. Dr. Clement is a U. S. Public Health Service International Fellow on leave from the State University of Ghent, Belgium. Received September 14, Accepted for publication May 7, and artificially ventilated at cycles/min. Additional doses of chloralose (10 mg/kg, iv) were administered to maintain an even plane of anesthesia. Heparin (3 mg/kg, iv) was given prior tocannulation of the vessels and hourly thereafter (1 mg/kg, iv). Arterial Po, was maintained above 250 by ventilating with oxygen; Pco, was kept between 30 and 40 by adjusting the tidal volume. Bicarbonate was infused as needed to maintain the ph between 7.30 and Both vagi were sectioned in the neck. Both carotid sinuses were isolated according to the Moissejeff technique (3). The pressure within the sinuses was monitored, set at the level of the mean aortic blood pressure at the beginning of the experiment, and held constant thereafter. Gracilis Muscle Perfusion. All of the vessels to the left gracilis muscle were tied except the gracilis artery and vein. The gracilis artery was dissected free up to its entrance into the muscle, and all of the collaterals were tied. The gracilis artery was perfused either by inserting a catheter into it or by perfusing an isolated part of the femoral artery. Vascular isolation of the preparation was proved by anatomic isolation of the muscle or by the observation that the outflow from the gracilis vein decreased rapidly to zero when the infusion pump was stopped. Perfusion of Paw. The paw was perfused according to the technique described by Calvelo and associates (2). The left cranial tibial artery was exposed 3-4 cm craniad from the tarsus, and the collaterals at that level were tied. The left femoral artery was tied below the origin of the gracilis artery; the saphenous artery was tied at its origin as well as at the anastomosis with the dorsal pedal artery. The absence of significant collateral arterial Circulation Research. Vol. 35. Augutt

2 178 CLEMENT. SHEPHERD blood supply to the paw was shown by the absence of back flow after the artery was cut and was confirmed by the abrupt decrease in perfusion pressure to mm Hg when the perfusion pump was stopped. Moreover, when the arterial blood pressure was increased, after left lumbar sympathectomy, by electrically stimulating the right femoral nerve or decreasing the pressure in both carotid sinuses, the perfusion pressure in the paw did not change or changed only to a limited extent (5 ). Lateral Saphenous Vein Perfusion. The left lateral saphenous vein was cannulated at the ankle and perfused according to the technique described by Webb- Peploe and Shepherd (4). Under these conditions, the driving pressure, i.e., the difference between perfusion (inflow) pressure and femoral vein (outflow) pressure, is a measure of tone in the venous wall. There were no significant changes in femoral vein pressure in the experiments in the present study; thus, the changes in perfusion pressure were proportional to the changes in resistance in the lateral saphenous vein. The gracilis artery, the cranial tibial artery, and the lateral saphenous vein of the left hind limb were perfused at constant flow with a roller pump using autologous blood drawn from the left femoral or iliac artery. A depulsator and a heat exchanger were interposed in the perfusion line, and the temperature of the blood was maintained at 37 C. The perfusion pressure was measured just proximal to the point of insertion of the cannula into the artery. For the resistance vessels, the pump speed was adjusted at the beginning of each experiment to provide a perfusion pressure that was higher than the mean aortic blood pressure; this higher pressure compensated for the resistance of the cannulas and provided an inflow pressure to the gracilis and cranial tibial arteries that approximated the mean aortic blood pressure. For the lateral saphenous vein, the pump speed was adjusted to obtain a venous pressure between 20 and 50. MEASUREMENTS All pressures were measured with strain-gauge transducers (Statham P23De) and recorded on an ultraviolet Visicorder (Honeywell 1508). Aortic blood pressure was measured via a catheter inserted into the right brachial artery. STIMULATION OF MUSCLE AFFERENTS Muscle Stimulation. Square-wave stimuli were provided by a Grass S4 stimulator and two pairs of electrodes; one pair of electrodes was inserted into the right anterior thigh muscles and the other pair was inserted into the right posterior thigh muscles. The two poles of each pair of electrodes were kept 5 cm apart. The applied voltage was measured directly on the stimulating electrodes. The voltage used was that which caused maximal contraction to the thigh muscles without causing obvious contraction of other muscles. A train of 5-msec stimuli was delivered for 1 minute. Frequencies of 5 Hz and 40 Hz were used; 5 Hz caused rhythmic muscular contractions and 40 Hz caused a sustained tetanic contraction. Nerve Stimulation. The right femoral nerve was sectioned, and the central end was stimulated at 1 v and 5 Hz (at the electrodes) and at 5 v and 40 Hz for 1 minute. Stimulus duration was 1 msec. ROLE OF MUSCLE CONTRACTION The role of muscle contraction in the production of the vascular responses was investigated by stimulating the muscles before and after muscle paralysis induced by gallamine (3 mg/kg). BLOCKADE OF VASCULAR RESPONSES The following drugs were used to antagonize the vascular responses: atropine sulfate (0.2 mg/kg), propranolol (1 mg/kg), tripelennamine (1 mg/kg), and phenoxybenzamine (3 mg/kg). These drugs were infused upstream from the pump perfusing the vascular bed under study. To test the effectiveness of the antagonists, acetylcholine (0.5 jig/kg), isoproterenol HC1 (0.05 Mg/kg), histamine phosphate (0.05 tig/kg), and norepinephrine bitartrate (0.05 ng base/kg) were injected before and after the corresponding blocking agent. In four dogs, the left sympathetic chain was removed from L4 to L6. This procedure has been shown to eliminate most of the sympathetic supply to the hind limb (5). Results CHANGES IN PERFUSION PRESSURE IN MUSCLE AND PAW DURING ELECTRICAL STIMULATION OF HIND-LIMB MUSCLE In eight dogs, the effect of electrical stimulation of the right hind-limb muscles was investigated (Table 1 and Fig. 1). At 5 Hz, there was a decrease in perfusion pressure in the gracilis muscle and the paw. In some dogs (Fig. 1), this decrease was larger in the gracilis muscle than it was in the paw; however, the mean decrease was comparable. Stimulation at 40 Hz caused an increase in perfusion pressure in both the gracilis muscle and the paw. CHANGES IN PERFUSION PRESSURE IN LATERAL SAPHENOUS VEIN AND IN AORTIC BLOOD PRESSURE DURING ELECTRICAL STIMULATION OF HIND-LIMB MUSCLES The reaction of the lateral saphenous vein was opposite to that of the resistance vessels in muscle and paw (Table 1 and Fig. 2). At 5 Hz, there was an increase in the perfusion pressure in the vein; at 40 Hz the perfusion pressure was decreased. However, the reaction of aortic blood pressure was in the same direction as that of the resistance vessels in muscle and paw. CHANGES IN PERFUSION PRESSURE AND AORTIC BLOOD PRESSURE DURING ELECTRICAL STIMULATION OF RIGHT FEMORAL NERVE The effect of stimulation of the femoral nerve was analyzed in all 13 dogs. At 5 Hz and 1 v, femoral nerve stimulation caused a mean decrease in perfusion pressure in the gracilis muscle and the paw of 31 ± 5 (SE) and 26 ± 5, respectively, and a mean increase in perfusion pressure in the lateral saphenous vein of 11 ± 3 mm Hg. At 40 Hz and 5 v, perfusion pressure in the gracilis muscle and the paw increased 24 ± 3 mm Hg and 21 ± 4, respectively. The perfusion Circulation Research, Vol. 35. August 1974

3 MUSCLE AFFERENTS AND PERIPHERAL VESSELS 179 TABLE 1 Effect of Electrical Stimulation of Right Hind-Limb Muscles on Perfusion Pressure in Cutaneous and Muscle Vessels of the Left Hind Limb and on Aortic Blood Pressure Mean change ± SE (N - 8) At 5 Hz At 40 Hz Site %* %* Saphenous vein Paw Gracilis muscle Aorta + 13 ±3-26 ±5-26±6-45 ±8 +33 ±6-16 ±4-22 ±5-30 ±5-20 ±2 +33 ±3 +33 ± ±8-35 ± ± ±4 +25 ±4 * Percent of control pressure just before onset of stimulation. pressure in the lateral saphenous vein decreased 14 ± 4. Aortic blood pressure decreased 41 ± 5 during stimulation at 5 Hz and increased 58 ± 7 during stimulation at 40 Hz. ROLE OF MUSCLE CONTRACTION The role of muscle contraction in the production of the vascular responses was investigated in eight dogs (Fig. 3). After muscle paralysis, the reaction to stimulation at 5 Hz was similar to the control MUSCLE AT STIMULATION 5 Hz MUSCLE AT STIMULATION 40 Hz Paw 0 <- Gracilis Muscle I minute 4v 5 Hz 4v 4 0 Hz FIGURE 1 Changes in perfusion pressure in left paw and gracilis muscle during stimulation of right hind-limb muscles at 5 Hz (left) and 40 Hz (right). Paw and gracilis muscle were perfused at constant flow. Stimulation at 5 Hz caused rhythmic muscular contractions; stimulation at 40 Hz caused a tetanic contraction. ZOO t O - 4v 5 Hz 4 v 40 Hz FIGURE 2 Changes in perfusion pressure in left gracilis muscle and lateral saphenous vein during stimulation of right hind-limb muscles at 5 Hz (left) and 40 Hz (right). The reaction of the saphenous vein was opposite in direction to that of the gracilis artery and aortic blood pressure. Circulation Research. Vol. 35. AuguMt 1974

4 180 CLEMENT, SHEPHERD reaction. Perfusion pressure decreased 29 ± 9 mm Hg in the gracilis muscle and 16 ± 2 in the paw, and the perfusion pressure increased 13 ± 3 in the vein. Aortic blood pressure decreased 34 ± 5. In contrast, the response to stimulation at 40 Hz was abolished or, in some dogs, reversed. After paralysis, there was no significant change in the perfusion pressure in the paw or the vein, although the perfusion pressure in the gracilis muscle and the aortic blood pressure decreased 12 ± 2 and 19 ± 5, respectively. EFFERENT PATHWAY OF REFLEX VASCULAR RESPONSES In eight dogs, the efferent pathway was analyzed in response to stimulation of the femoral nerve. Atropine did not affect the response to stimulation at 5 Hz or 40 Hz (Fig. 4). After administration of atropine, stimulation of the femoral nerve at 1 v and 5 Hz caused a decrease in aortic blood pressure of 30 ± 7 and in perfusion pressure in muscle and paw of 20 ± 4 and 20 ± 6 mm Hg, respectively, and an increase in perfusion pressure in the saphenous vein of 7 ± 2. At 5 v and 40 Hz, aortic blood pressure increased 47 ± 5, perfusion pressure in the muscle and the r Mean Aorta 4v CONTROL 5 Hz Paw FV paw increased 25 ± 5 and 16 ± 2, respectively, and perfusion pressure in the saphenous vein decreased 20 ± 6. In three dogs, stimulations at 5 Hz and 40 Hz were performed before and after the administration of propranolol and tripelennamine; neither drug influenced the vascular responses, although the vasodilation caused by isoproterenol or histamine was almost completely abolished. In contrast, in four dogs, phenoxybenzamine abolished the vascular responses to stimulation at 5 Hz and 40 Hz. In four other dogs, left sympathectomy abolished the responses in the vascular beds studied. At 1 v and 5 Hz, there was a decrease of 20 ± 6 in aortic blood pressure but no significant change in the perfusion pressures; at 5 v and 40 Hz, there was an increase of 46 ± 11 in aortic blood pressure but no significant change in the perfusion pressures. The vessels were still reactive, because norepinephrine injected upstream from the pump always increased the perfusion pressure in the three vessels studied. Discussion Stimulation at 5 Hz, which elicited rhythmic muscle contractions, caused a decrease in the AFTER MUSCLE PARALYSIS p MA Saphenous Vein Femoral Vein 4v 5 Hz ^ I min SV FV FV 4v 40 Hz 4v 40 Hz FIGURE 3 Effect of muscle paralysis on changes in perfusion pressure in the left paw and the lateral saphenous vein during stimulation of the right hind-limb muscles at 5 Hz (top) and 40 Hz (bottom). Response to 5-Hz stimulation was unaffected by muscle paralysis, but the response to 40-Hz stimulation was prevented. Circulation Research, Vol. 35, August 1974

5 MUSCLE AFFERENTS AND PERIPHERAL VESSELS 181 mm H 1 Aorta CONTROL Gracilis Muscle MA AFTER ATROPINE p AFTER PHENOX YBENZA MINE p ^== ^ MA "\ -^~ 0 lv 5 Hz lv 5 Hz lv 5 Hz MA I min 0 L 5v 40 Hz 5v 40 Hz FIGURE 4 5V 40 HZ Effect of atropine and phenoxybemamine on changes in perfusion pressure in the left paw and the left gracilis muscle during stimulation of the central end of the right femoral nerve at 1 v and 5 Hz (top) and at 5 v and 40 Hz (bottom). The responses were unaffected by atropine but were attenuated or abolished by phenoxybemamine perfusion pressure in the resistance vessels in the muscle and the paw along with a decrease in the aortic blood pressure; stimulation at 40 Hz, which elicited a tetanic contraction, caused an increase in these pressures. The reaction of the lateral saphenous vein was opposite to that of the resistance vessels; stimulation at 5 Hz caused an increase in the perfusion pressure and stimulation at 40 Hz caused a decrease. The afferent pathway of these responses is in the somatic nerve fibers from the contracting muscles. A previous study (1) has shown that the responses in the hind limb are abolished or markedly attenuated after the right femoral, sciatic, and obturator nerves are cut but are unaffected by right sympathectomy. Moreover, stimulation of the femoral nerve, which is mainly a muscle nerve (6), causes similar responses. The influences from the high- and low-pressure receptors were eliminated or kept constant in these experiments by isolating both carotid sinuses and cutting the vagosympathetic trunk in the neck. The efferent pathway of these vascular responses is mediated by the adrenergic sympathetic nerves. Sympathectomy or alpha-receptor blockade abolishes both the depressor and the pressor response. The vasodilation is not due to activation of cholin- Circulation Research, Vol. 35, August 1974 ergic fibers (7) because the responses are not prevented by atropine, and it is not caused by activation of histaminergic or beta receptors because the responses are unaffected by tripelennamine and propranolol. Thus, the depressor and the pressor responses probably are caused by a decrease and an increase in adrenergic activity, respectively. This conclusion agrees with experimental findings in the cat in which, depending on the type of fibers activated, a decrease or an increase in sympathetic activity results from stimulation of somatic nerve fibers from muscle (8-11). The experiments in the present study confirm previous observations (1, 12, 13) about the role of muscle contraction in the production of these vascular responses. Muscle paralysis did not prevent the response to stimulation of the muscles at 5 Hz; thus, it is likely that the electrical stimulation caused a direct activation of nerve fibers in the muscles. Similar responses were observed when the femoral nerve was stimulated centrally, and the responses of the resistance vessels and the aortic blood pressure agreed with the results obtained during direct stimulation of somatic nerves from muscle, thoracic nerves II and IE, and dorsal roots L7-S1 in the cat (11, 14-19). However, muscle paralysis abolished or reversed the response to

6 182 CLEMENT. SHEPHERD stimulation at 40 Hz in agreement with observations on the aortic blood pressure and hind-limb blood flow during tetanic muscle contractions in the cat (12, 13). Thus, muscle contraction appears to be required for activation of the afferent fibers which initiate an increase in sympathetic activity to the resistance vessels and a decrease in sympathetic activity to the saphenous vein. Johansson (16) and Khayutin (17) have studied the vascular responses of muscle, skin, kidney, intestine, spleen, and liver to stimulation of afferent nerves from muscle in the cat; the responses observed in these different vascular beds were always in the same direction. The cutaneous veins were not investigated in their studies (16, 17), but these veins are known to respond differently from other vascular beds. For example, the cutaneous veins do not react to activation of the high-pressure (20-22) and low-pressure mechanoreceptors (23); chemoreceptor activation causes constriction of the resistance vessels in muscle, dilation of the resistance vessels in the paw (2), and dilation of the cutaneous veins (24). Changes in body temperature cause the vessels in the skin to react vigorously (25-31), but the vessels in the muscle remain unaffected (32). The experiments in the present study show that, during stimulation of somatic afferents from muscle, the reaction of cutaneous veins is opposite in direction to that of the resistance vessels in the muscle and the paw. These data provide further evidence for a selective autonomic nervous control of different components of the vascular system. Acknowledgment The authors thank Gary F. Burton for his technical assistance and Mrs. Joan Y. Troxell for preparation of the manuscript. References 1. CLEMENT DL, PELLETIER CL, SHEPHERD JT: Role of muscular contraction in the reflex vascular responses to stimulation of muscle afferents in the dog. Circ Res 33: , CALVELO MG, ABBOUD FM, BALLARD DR, ABDEL-SAYED W: Reflex vascular responses to stimulation of chemoreceptors with nicotine and cyanide. Circ Res 27: , MOISSEJEFT E: Zur Kenntnis des Carotissinusreflexes. Z G*samte Exp Med 53: , WEBB-PEPLOE MM, SHEPHERD JT: Response of large hindlimb veins of the dog to sympathetic nerve stimulation. Am J Physiol 215: , DONALD DE, FERGUSON DA: Study of the sympathetic vasoconstrictor nerves to the vessels of the dog hind limb. Circ Res 26: , MILLER ME: Anatomy of the Dog. Philadelphia, W. B. Saunders Company, UVNAS B: Sympathetic vasodilator outflow. Physiol Rev 34: , FEDINA L, KATUNSKII AY, KHAYUTIN VM, MITSANYI A: Responses of renal sympathetic nerves to stimulation of afferent A and C fibres of tibial and mesenterial nerves. Acta Physiol Acad Sci Hung 29: , SATO A, KAUFMAN A, KOIZUMI K, BROOKS CMCC: Afferent nerve groups and sympathetic reflex pathways. Brain Res 14: , KOEUMI K, SATO A, KAUFMAN A, BROOKS CMCC: Studies of sympathetic neuron discharges modified by central and peripheral excitation. Brain Res 11: , KOIZUMI K, COLLIN R, KAUFMAN A, BROOKS CMCC: Contribution of unmyelinated afferent excitation to sympathetic reflexes. Brain Res 20:99-106, KUCERA J: Vasomotor reflexes from muscles in the spinal cat. Experientia 25: , COOTE JH, HILTON SM, PEREZ-GONZALEZ JF: Reflex nature of the pressure response to muscular exericse. J Physiol (Lond) 215: , SKOGLUND CR: Vasomotor reflexes from muscle. Acta Physiol Scand 50: , LAPORTE Y, BESSOU P, BOUISSET S: Action reflexe des differents types de fibres afferentes d'origine musculaire sur la pression sanguine. Arch Hal Biol 98: , JOHANSSON B: Circulatory responses to stimulation of somatic afferents with special reference to depressor effects from muscle nerves. Acta Physiol Scand [Suppl] 198:1-91, KHAYUTIN VM: Specific and non-specific responses of the vasomotor centre to impulses of spinal afferent fibres. Acta Physiol Acad Sci Hung 29: , DE MOLINA AF, PERL EF: Sympathetic activity and the systemic circulation in the spinal cat. J Physiol (Lond) 181:82-102, LAPORTE Y, LEITNER L-M, PAGES B: Absence d'effets reflexes circulatoires des fibres afferentes du groupe I. C R Soc Biol (Paris) 156: , BEVEGXRD BS, SHEPHERD JT: Circulatory effects of stimulating the carotid arterial stretch receptors in man at rest and during exercise. J Clin Invest 45: , BROWSE NL, DONALD DE, SHEPHERD JT: Role of the veins in the carotid sinus reflex. Am J Physiol 210: , BRENDER D, WEBB-PEPLOE MM: Influence of-carotid baroreceptors on different components of the vascular system. J Physiol (Lond) 205: , PELLETIER CL, EDIS AJ, SHEPHERD JT: Circulatory reflex from vagal afferents in response to hemorrhage in the dog. Circ Res 29: , PELLETIER CL, SHEPHERD JT: Venous responses to stimulation of carotid chemoreceptors by hypoxia and hypercapnia. Am J Physiol 223:97-103, SHEPHERD JT: Nervous control of the blood vessels in the skin. In Physiology of the Circulation in Human Limbs in Health and Disease, edited by JT Shepherd. Philadelphia, W. B. Saunders Company, 1963, p WEBB-PEPLOE MM, SHEPHERD JT: Responses of the superficial limb veins of the dog to changes in temperature. Circ Res 22: , WEBB-PEPLOE MM, SHEPHERD JT: Response of dogs' cutaneous veins to local and central temperature changes. Circ Res 23: , WEBB-PEPLOE MM: Effect of changes in central body temperature on capacity elements of limb and spleen. Am J Physiol 216: , 1969 Circulation Research, Vol. 35, August 1974

7 MUSCLE AFFERENTS AND PERIPHERAL VESSELS VANHOUTTE PM, SHEPHERD JT: Effect of temperature on 31. ZITODC RS, AMBROSIONI E, SHEPHERD JT: Effect of tempera - reactivity of isolated cutaneous veins of the dog. Am J ture on cutaneous venomotor reflexes in man. J Appl Physiol 218: , 1970 Physiol 31: , VANHOUTTE PM, LORENZ RR: Effect of temperature on 32. EDHOLM OG, FOX RH, MACPHERSON RK: Effect of body reactivity of saphenous, mesenteric, and femoral veins of heating on the circulation in skin and muscle. J Physiol the dog. Am J Physiol 218: , 1970 (Lond) 134: , 1956 Circulation Research. Vol. 35. August 1974