Muscle Blood Flow In Rats Research Articles

Effects of olfactory stimulation with scents of grapefruit and lavender essential oils on the skeletal muscle sympathetic nerve and muscle blood flow in rats

AbstractWe have previously observed that olfactory stimulation with scents of grapefruit and lavender oils have opposing effects on autonomic neurotransmission and physiological phenomena in rats. Since the suppression and facilitation of activity of the sympathetic nerves innervating the skeletal muscles decreases and increases the skeletal muscle blood flow (skeletal muscle‐BF), respectively, the effects of olfactory stimulation with scent of a grapefruit essential oil (SGFO) and scent of a lavender essential oil (SLVO) on skeletal muscle sympathetic nerve activity (skeletal muscle‐SNA) and skeletal muscle‐BF were examined. SGFO reduced, and SLVO elevated skeletal muscle‐SNA and skeletal muscle‐BF, respectively. Furthermore, 1) anosmic treatment with ZnSO4 eliminated the changes in skeletal muscle‐SNA due to SGFO and SLVO, 2) diphenhydramine, a histamine H1‐antagonist, eliminated the SGFO‐induced suppression of skeletal muscle‐SNA, and thioperamide, a histamine H3‐antagonist, abolished the SLVO‐induced enhancement of skeletal muscle‐SNA, and 3) butoxamine, an adrenergic β2‐antagonist, blocked the SLVO‐induced increase in skeletal muscle‐BF. These findings suggest that olfactory stimulation with SGFO reduces, and SLVO enhances, skeletal muscle‐BF via these autonomic changes. In addition, the histamine H1‐receptor was found to be involved in the SGFO‐induced suppression of skeletal muscle‐SNA, the H3‐receptor was shown to be concerned to the SLVO‐induced enhancement of skeletal muscle‐SNA, and the adrenergic β2‐receptor was indicated to be implicated in the SLVO‐induced increase in skeletal muscle‐BF via an increase in skeletal muscle‐SNA. These findings suggest that SGFO may suppress, and SLVO may enhance, the muscle recovery from muscle fatigue and the growth of muscles, via changes in autonomic neurotransmission.

Contributions of ADP and ATP to the increase in skeletal muscle blood flow after manual acupuncture stimulation in rats.

To investigate the contributions of adenosine triphosphate (ATP) and adenosine diphosphate (ADP) to the increase in skeletal muscle blood flow (MBF) observed following manual acupuncture (MA) stimulation in rats. Male Sprague-Dawley rats were used as experimental animals (300-370 g, n=40). MA was applied to the right tibialis anterior muscle (TA) for 1 min using a stainless steel acupuncture needle. In eight rats, high-performance liquid chromatography with the microdialysis technique was used to measure local extracellular concentrations of ATP, ADP, adenosine monophosphate (AMP), and adenosine in the TA. In the remaining 32 rats, fluorescent microspheres (15 µm in diameter) were used to measure MBF in the TA following pre-treatment with either the P2 receptor antagonist suramin (100 mg/kg intra-arterially) or saline (control) (n=16 each). Rats receiving MA (Suramin+MA and Saline+MA groups, n=8 each) were compared with untreated rats (Suramin and Saline groups, n=8). MA significantly increased the local extracellular concentration of ATP, ADP, and adenosine (p<0.05, before MA vs 30 min after MA). In addition, MA significantly increased MBF in rats pre-treated with saline or suramin (p<0.01, Saline vs Saline+MA; p<0.05, Suramin vs Suramin+MA, respectively). However, suramin significantly suppressed this MA-induced increase in MBF (p<0.05, Saline+MA vs Suramin+MA). These results suggest that both ATP and ADP partially contribute to the MA-induced increase in MBF via P2 receptors. However, further studies are needed to clarify the contributions of other vasodilators.

Assessment by Thallium-201 of Hindlimb Muscle Blood Flow in Rats during Recovery after Hindlimb Unloading

[Purpose] We aimed to evaluate the muscle blood perfusion by the uptake of the radioisotope thallium-201 (201Tl) in 5 hindlimb muscles, the soleus (Sol), plantaris (Pla), gastrocnemius (Gas), extensor digitorum longus (EDL), and tibialis anterior (TA). [Subjects] The subjects were 36 male Wistar rats. [Methods] 201Tl uptake rates were calculated by spectrometry and visualized by autoradiography (ARG) in hindlimb unloading (U) and reloading (R) rats. [Results] The Sol 201Tl uptake rates were significantly lower in U groups (p<0.01) than in the control group. Meanwhile the reloading day-4 group had higher values in Sol than the control (p<0.01). In U groups, the EDL and TA uptake rates were higher than in the other 3 muscles (Sol, Pla, and Gas). [Conclusion] We concluded that during 21 days of hindlimb unloading and subsequent recovery by reloading, blood capillary perfusion assessed by 201Tl in hindlimb muscles changes in rats. The results confirm the utility of 201Tl in quantitative and qualitative evaluation of skeletal muscle activity and blood perfusion, which has applications in rehabilitation and sports science.

Interaction of Femoral Artery Ligation and TVaining on Microvascular PO2 and Blood Flow in Rat Soleus Muscle

The microvascular PO2 (PmO2) reflects the dynamic balance between oxygen delivery and oxygen uptake, and is the driving force for oxygen flux into muscle cells. Femoral artery ligation reduces hindlimb muscle blood flow in rats which is partially restored with the development of collateral circulation, and is enhanced with exercise training (Am J Physiol 287: H2434, 2004). It is not known how effectively this collateral circulation restores oxygen delivery. PURPOSE: To test the hypothesis that increased collateral flow would restore PO2m and that this would be enhanced with exercise training. METHODS: The left femoral artery of female Sprague-Dawley rats (∼275 g) was either left intact (sham) or double-ligated. Sham and ligated rats were divided into four experimental groups; sedentary sham (SED-SH; n=10), sedentary ligated (SED-LIG; n=12), exercise trained sham (ET-SH; n=8), and exercise trained ligated (ET-LIG; n=10). Daily treadmill training began 48 hrs after surgery. The exercise intensity and duration were increased progressively to 17 m/min (at 20 degrees) for up to 60 min/day, as tolerated. Experiments were performed 21–28 days later. PmO2 (phosphorescence quenching) and blood flow (radiolabeled microspheres) were measured in the left soleus muscle at rest and during 1 Hz contractions. RESULTS: Soleus PmO2 in the SED-LIG rats was lower than in the SED-SH rats (33 ± 3 vs. 19 ± 3 mmHg). Training did not alter resting PmO2 (ET-SH, 33 ± 2; ET-LIG, 19 ± 2 mmHg). During contractions, PmO2 was lower in the SED-LIG (19 ± 3 mmHg) compared to SED-SH (28 ± 3 mmHg). In contrast, PmO2 during contractions in the trained groups was higher than the sedentary groups (ET-SH, 35 ± 4; ET-LIG, 26 ± 3 mmHg). Soleus blood flow during contractions was less in the SED-LIG rats (27 ±13 vs. 64 ± 14 ml/min/100 g). Soleus flow was doubled in ET-SH rats, but was unchanged in ET-LIG rats (140 ± 18 and 34 ± 15 ml/min/100 g). CONCLUSIONS: Even after chronic femoral artery ligation, there were marked deficits in blood flow and PmO2 in the soleus muscle. Low intensity training increased PmO2 during contractions in the femoral artery ligated rats. This was not associated with an increase in blood flow, and suggests there was a redistribution of flow to support oxygen delivery to the working muscle.

Angiotensin‐Converting Enzyme Inhibition Increases Exercise Tolerance and Muscle Blood Flow in Rats with Peripheral Arterial Insufficiency

To determine the effect of angiotensin-converting enzyme (ACE) inhibition on exercise tolerance and muscle blood flow (BF) to ischemic limbs, both femoral arteries of male Sprague-Dawley rats (approximately 325 g) were surgically stenosed. Rats were either active (treadmill run, 20 m/min (a) 15% grade, 5 d/wk for 3 wk) or sedentary (limited to cage activity), and assigned to one of three doses of zabicipril at 0.0 (zero), 0.3 (low), and 3.0 (high) mg.kg-1.d-1 administered via food intake (N = 14-15/group). After 3 weeks, the left carotid and caudal arteries were catheterized under anesthesia for BF measurement later in the day. Muscle BF was determined during exercise at two treadmill speeds (20 and 30 m/min) with 85Sr and 141Ce labeled microspheres to ensure a peak BF. Plasma ACE was inhibited 31%, 65% in the low- and high-dose sedentary rats and 75%, 74% in the low- and high-dose active animals, respectively (P < 0.001). Angiotensin-converting enzyme inhibition improved exercise tolerance by 3 weeks, at a low speed (20 m/min) in the sedentary groups (P < 0.025) and in a dose-dependent manner at a higher speed (25 m/min) in the active groups (P < 0.001). Blood pressures and heart rates during running were not different among groups. However, total hindlimb BF, reduced to approximately 33% of normal by femoral stenosis, was increased by ACE inhibition and chronic activity in a dose-dependent manner (P < 0.025). Blood flows to the plantar flexors were most improved (approximately 20-40%; to 124 mL.min-1 x 100 g-1) in the high-dose groups (P < 0.01). The higher run speed did not increase BF above the low speed. Training adaptation, indicated by an enhanced muscle mitochondrial content (P < 0.001), was similar for low- and high-dose active animals. Our results indicate that ACE inhibition improves BF to ischemic muscles and, together with chronic physical activity, improves exercise tolerance. The results from this study support those advocating ACE inhibition in managing appropriate patients with peripheral arterial insufficiency.

Effects of high-intensity sprint training on skeletal muscle blood flow in rats

The regional blood flow response (via radioactive microspheres) was determined for female rats after 6 wk of high-intensity sprint training (HIST) or limited cage activity as the animals exercised at work loads that would elicit maximal O2 uptake. Blood flow to the different organs of the abdominal region was greatly reduced during maximal exercise conditions, and the magnitude of the reduction appeared to be similar for both the HIST group of rats and their sedentary (SED) control counterparts. Of the 20 different hindlimb muscles examined in the present study, blood flow to the soleus, plantaris, gastrocnemius, flexor hallicus longus, vastus lateralis, rectus femoris, biceps femoris, and adductor magnus and brevis muscles was significantly greater (P less than 0.05) in the HIST rats during maximal exercise conditions than in the SED control rats. Correspondingly, blood flow to the total hindlimb during maximal exercise was also significantly greater in the HIST rats than in the SED control rats [240 +/- 18 vs. 192 +/- 15 (SE) ml.min-1.100 g-1]. These results support the contention that the increase in maximal cardiac output that is produced by HIST in the rat is primarily directed toward the working skeletal muscle and not toward the organs found in the abdominal region. We conclude from these experiments that HIST will produce significant adaptations in central cardiac function and skeletal muscle blood flow in the rat.

Training increases muscle blood flow in rats with peripheral arterial insufficiency

This study investigated the effect of physical training on muscle blood flow (BF) in rats with peripheral arterial insufficiency during treadmill running. Bilateral stenosis of the femoral artery of adult rats (300-350 g) was performed to reduce exercise hyperemia in the hindlimb but not limit resting muscle BF. Rats were divided into normal sedentary, acute stenosed (stenosed 3 days before the experiment), stenosed sedentary (limited to cage activity), and stenosed trained (run on a treadmill by a progressively intense program, up to 50-60 min/day, 5 days/wk for 6-8 wk). Hindlimb BF was determined with 85Sr- and 141Ce-labeled microspheres at a low (20 m/min) and high treadmill speed (30-40 m/min depending on ability). Maximal hindlimb BF was reduced to approximately 50% normal in the acute stenosed group. Total hindlimb BF (81 +/- 5 ml.min-1.100 g-1) did not change in stenosed sedentary animals with 6-8 wk of cage activity, but a redistribution of BF occurred within the hindlimb. Two factors contributed to a higher BF to the distal limb muscle of the trained animals. A redistribution BF within the hindlimb occurred in stenosed trained animals; distal limb BF increased to approximately 80% (P less than 0.001) of the proximal tissue. In addition, an increase in total hindlimb BF with training indicates that collateral BF has been enhanced (P less than 0.025). The associated increase in oxygen delivery to the relatively ischemic muscle probably contributed to the markedly improved exercise tolerance evident in the trained animals.

Sympathetic neural influences on muscle blood flow in rats during submaximal exercise.

These experiments were designed to estimate the involvement of the sympathetic innervation in regulation of hindlimb muscle blood flow distribution among and within muscles during submaximal locomotory exercise in rats. Blood flows to 32 hindlimb muscles and 13 other selected tissues were measured using the radiolabeled microsphere technique, before exercise and at 0.5, 2, 5, and 15 min of treadmill exercise at 15 m/min. The two groups of rats studied were 1) intact control, and 2) acutely sympathectomized (hindlimb sympathectomy accomplished by bilateral section of the lumbar sympathetic chain and its connections to the spinal cord at L2-L3). There were no differences in total hindlimb muscle blood flow among the two groups during preexercise or at 30 s or 2 min of exercise. However, flow was higher in eight individual muscles at 2 min of exercise in the sympathectomized rats. At 5 and 15 min of exercise there was higher total hindlimb muscle blood flow in the denervated group compared with control. These differences were also present in many individual muscles. Our results suggest that 1) sympathetic nerves do not exert a net influence on the initial elevations in muscle blood flow at the beginning of exercise, 2) sympathetic nerves are involved in regulating muscle blood flow during steady-state submaximal exercise in conscious rats, and 3) these changes are seen in muscles of all fiber types.

A method for using microspheres to measure muscle blood flow in exercising rats.

A catheter-implantation procedure allowing use of the radiolabeled microsphere (MS) technique for measuring skeletal muscle blood flow (BF) in rats during high-speed treadmill running was desired. Attempts to use existing procedures were unsuccessful. We found that Silastic catheters (0.02 in. ID X 0.037 in. OD) placed in the ascending aorta (for MS infusions) and the renal artery (for reference sample withdrawal) minimized these exercise performance problems. It was then necessary to establish that aortic MS infusions result in good MS-blood mixing. We tested the method with the following: 1) the radioactivities found in reference withdrawal samples taken from two locations in the aorta were compared after left ventricular (LV) infusion and after aortic infusion; 2) BFs to bilaterally paired tissues were compared in anesthetized and conscious rats with LV and aortic infusions; 3) the distribution of MSs in the muscles was studied histologically; and 4) BFs in bilaterally paired tissues were compared in rats with aortic MS infusions during treadmill running. The results indicate that 1) the percent difference between the radioactivities found in the proximal and distal reference withdraw samples was the same for LV and aortic MS infusions; 2) BF to bilaterally paired tissue samples was the same with both LV or aortic MS infusions; 3) the MSs were distributed uniformly within muscles, and MS aggregation was not a significant problem; and 4) BFs to bilaterally paired tissue samples were the same in exercising rats. We conclude that this technique can be used to measure muscle BF in rats running on a treadmill.