Approach using the bath preparation containing rice extract for severe pruritus in a patient receiving hemodialysis: A case report.

Severe pruritus in a hemodialysis patient who had difficulty applying topical medication markedly reduced with the use of bath preparation containing rice extract. The bath preparation could be effective and an option for treating pruritus.

Comprehensive relationship between disease activity indices, mTSS, and mHAQ and physical function evaluation and QOL in females with rheumatoid arthritis.

Rheumatoid arthritis (RA) causes significant physical disability. We comprehensively investigated the relationship between RA disease activity (Disease Activity Score 28-C-reactive protein [DAS28-CRP], Simplified Disease Activity Index [SDAI], and Clinical Disease Activity Index [CDAI]), physical function (10-Meter Walk Test [10 MWT], Timed Up and Go test [TUG], Functional Reach Test [FRT], and Disabilities of the Arm, Shoulder, and Hand [DASH]), and quality of life (QOL) (Short-Form 36 [SF-36®]). We also investigated the relationship between van der Heijde's modified Total Sharp Score (mTSS), modified Health Assessment Questionnaire (mHAQ), and physical function and QOL assessments. Among 35 female patients with RA, DAS28-CRP correlated solely with DASH (r = 0.376), while SDAI and CDAI did not correlate with physical function. The mTSS-hand roentgenographic evaluation correlated with TUG (r = 0.359), FRT (r = - 0.415), and DASH (r = 0.533) among physical function assessments. The mHAQ correlated with 10 MWT (r = 0.347), TUG (r = 0.356), FRT (r = - 0.420), and DASH (r = 0.646). DAS28-CRP correlated with six of the eight subscales of SF-36®, and mTSS and mHAQ correlated with only one subscale. RA disease activity assessments may not reflect all physical functions and QOL domains of female patients with RA. Evaluating physical function and QOL in female patients with RA is essential.

A multicenter explanatory survey of patients' and clinicians' perceptions of motivational factors in rehabilitation.

BACKGROUND: Patient motivation is an important determinant of rehabilitation outcomes. Differences in patients' and clinicians' perceptions of motivational factors can potentially hinder patient-centered care. Therefore, we aimed to compare patients' and clinicians' perceptions of the most important factors in motivating patients for rehabilitation. METHODS: This multicenter explanatory survey research was conducted from January to March 2022. In 13 hospitals with an intensive inpatient rehabilitation ward, 479 patients with neurological or orthopedic disorders undergoing inpatient rehabilitation and 401 clinicians, including physicians, physical therapists, occupational therapists, and speech-language-hearing therapists, were purposively selected using inclusion criteria. The participants were asked to choose the most important factor motivating patients for rehabilitation from a list of potential motivational factors. RESULTS: Here we show that realization of recovery, goal setting, and practice related to the patient's experience and lifestyle are the three factors most frequently selected as most important by patients and clinicians. Only five factors are rated as most important by 5% of clinicians, whereas nine factors are selected by 5% of patients. Of these nine motivational factors, medical information (p < 0.001; phi = -0.14; 95% confidence interval = -0.20 to -0.07) and control of task difficulty (p = 0.011; phi = -0.09; 95% confidence interval = -0.16 to -0.02) are selected by a significantly higher proportion of patients than clinicians. CONCLUSIONS: These results suggest that when determining motivational strategies, rehabilitation clinicians should consider individual patient preferences in addition to using the core motivational factors supported by both parties.

Rehabilitation is the interventions needed to restore the abilities required for daily life following illness or injury. Patients and clinicians who provide these interventions may have different ideas about what encourages patients to engage in rehabilitation. It is important to understand what motivates patients and any differences in opinion between patients and clinicians. We asked patients and clinicians about the most important motivational factors. All agreed that realizing recovery is possible, setting goals or targets for the stages of recovery, and targeting interventions relevant to the patient's experience and lifestyle were the most important motivational factors. The patients also found access to medical information and being able to control the difficulty of tasks required during rehabilitation motivating. These findings could help clinicians provide rehabilitation care that is more specifically tailored to each patient's needs and preferences.

Measuring Muscle Activity in the Trunk, Pelvis, and Lower Limb Which Are Used to Maintain Standing Posture in Patients With Adult Spinal Deformity, With Focus on Muscles that Contract in the Compensatory Status.

STUDY DESIGN: Prospective single-center study. OBJECTIVE: This study aimed to investigate the muscle activity of the trunk, pelvis, and lower limb, which are used to maintain a standing posture in elderly patients with spinal deformities. We also elucidated the mechanism of compensation against spinal deformity in terms of muscle activity. METHODS: Any patient scheduled to undergo surgery for adult spinal deformity was included. Surface electromyography and radiography were performed preoperatively. The following four representative alignments were defined as compensations: 1. pelvic retroversion, 2. reduction in thoracic kyphosis, 3. hyperextension of the lumbosacral junction, and 4. knee flexion. Individual muscle activity was compared with and without compensation. The patients were stratified into three groups according to the severity of spinal compensation, and differences in muscle activity were compared. RESULTS: This study included 76 patients (7 men and 69 women, average age 69.4 years). Our results revealed that pelvic retroversion and knee flexion were compensations that required trunk muscle activity. In contrast, reduction of thoracic kyphosis and hyperextension of the lumbosacral junction did not require much trunk muscle activity. There was a significant difference in the muscle activity of the pelvis and lower limbs according to the severity of the deformity. CONCLUSIONS: In terms of muscle activity, compensation for regional alignment changes in the adjacent spine is economical. However, extra-spinal compensations, such as pelvic retroversion and knee flexion, are non-economical. According to compensation recruitment, the muscle activity of the pelvis and lower limbs increased with the severity of the spinal deformity.

Decline in Walking Independence and Related Factors in Hospitalization for Dialysis Initiation: A Retrospective Cohort Study.

Patients with chronic kidney disease require intervention planning because their physical function declines with worsening disease. Providers can work closely with patients during the induction phase of dialysis. This single-center, retrospective observational study aimed to investigate the rate of decline in walking independence during the induction phase of dialysis and the factors that influence this decline, and to provide information on prevention and treatment during this period. Of the 354 patients who were newly initiated on hemodialysis between April 2018 and January 2022, 285 were included in the analysis. The functional independence measure-walking score was used to sort patients into decreased walking independence (DWI; n = 46) and maintained walking independence (no DWI; n = 239) groups, and patient characteristics were compared. After adjusting for various factors by logistic regression analysis, we observed that age, high Charlson comorbidity index (CCI), C-reactive protein, and emergency dialysis start (EDS) were significant predictors of DWI. Even during the very short period of dialysis induction, as many as 16.1% of patients had DWI, which was associated with older age, higher CCI, higher inflammation, and EDS. Therefore, we recommend the early identification of patients with these characteristics and early rehabilitation.

Kidney Disease After Allogeneic Hematopoietic Stem Cell Transplantation Is Associated With Decreased Physical Function.

OBJECTIVE/BACKGROUND: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has improved outcomes and prognosis, but it has many complications and is associated with impaired physical function. To solve this problem, it is necessary to further analyze the factors that cause the decline in physical function. In the present study, we hypothesized that kidney disease following allo-HSCT would be associated with impaired physical function, in addition to conventional factors, and tested this hypothesis retrospectively. METHODS: Thirty-one patients who underwent allo-HSCT at the Department of Hematology in our hospital from January 2016 to October 2021 were included in the analysis. Correlation analysis and stepwise multiple regression analysis with change in 30-second sit to stand test (Δ30-s STS) as the dependent variable were performed to identify predictors of physical function decline from pretransplant to discharge. RESULTS: The mean age of participants was 43.9 years (SD = 11.8), the mean time from transplant to discharge was 103.1 days (SD = 35.0), and approximately 30% of patients had kidney disease following allo-HSCT. All patients were ambulatory and independent at discharge, but 30-s STS was significantly reduced (P < .001). Among various factors, age (ß = -0.464, P < .05), total corticosteroid dose (ß = -0.380, P < .05), and kidney disease after allo-HSCT (ß = -0.307, P < .05) were the independent predictors of Δ30-s STS (R2 = 0.592, adjusted R2 = 0.547, F = 13.072, P < .01). CONCLUSION: Kidney disease after allo-HSCT is one of the factors that may contribute to poor physical function, and patients who experience this condition may require additional follow-up to improve physical function.

Feasibility study of a LED light irradiation device for the treatment of chronic neck with shoulder muscle pain/stiffness.

Neck with shoulder muscle stiffness/pain is a common disorder. Commonly used physical therapy, pharmacotherapy, acupuncture, and moxibustion only temporarily alleviate the disorder in most cases, thus the disorder often recurs. Low power laser therapy is often used for neck and shoulder stiffness/pain and has been effective in clinical trials. In this study, we evaluated the safety and effectiveness of a newly developed self-care device for disorders including neck with shoulder muscle stiffness/pain. The device incorporates light-emitting diodes (LEDs), which are safer than lasers, as its light source. Ten adults with neck with shoulder muscle stiffness/pain were subject to LED irradiation (wavelength 780 nm ± 15 nm, output 750 mW, power density 3.8 W/cm2, energy density 5.7×102 J/cm2) for 3 minutes on the affected shoulder at a standard acupuncture point (GB21, Jianjing). Immediately after irradiation, the subjective symptoms of the neck with shoulder muscle stiffness and pain evaluated by a visual analog scale were improved from 58.3 mm ± 18.7 mm to 45.5 mm ± 21.5 mm and from 45.8 mm ± 23.3 mm to 39.4 mm ± 21.8 mm, respectively. The symptoms further improved after 15 minutes of irradiation. The skin temperature at the irradiated point increased from 34.3°C ± 1.1°C to 41.0°C ± 0.7°C. The increase in skin temperature was observed within approximately 5 cm of the irradiated area. There was no effect on the heart rate variability, a measure of the autonomic nervous system; however, the baroreflex sensitivity was slightly increased. No irradiation-related adverse skin events were observed. Our LED irradiation device was found to be safe, and it improved the subjective symptoms of muscle stiff neck with shoulders.

Rehabilitation of a Patient With Minimal Change Nephrotic Syndrome and Acute Kidney Injury: A Case Report.

Patients with minimal change nephrotic syndrome (MCNS) are prone to loss of motor skills due to urinary protein leakage, steroid myopathy, and other factors. Acute kidney injury (AKI) is a common complication that contributes to the loss of physical function. Rehabilitation is crucial, but its efficacy and safety are unknown. Here we present a case of a patient with MCNS complicated by AKI, who commenced rehabilitation after dialysis was discontinued and experienced improved mobility. The patient, a woman in her 70s, was admitted to our hospital with bilateral lower limb edema and decreased urine output for approximately 5 days. Treatment with prednisolone and furosemide was initiated, but then dialysis was initiated due to AKI. Rehabilitation was started after dialysis was discontinued. The patient's muscle strength and physical activity improved, and her exercise capacity and exercise tolerance improved without adverse effects. Rehabilitation may contribute to the improvement of exercise capacity without worsening renal function and urinary protein in patients with MCNS complicated by AKI.

Role of Subcutaneous Adipose Tissues in the Pathophysiology of Secondary Lymphedema.

Background: Secondary lymphedema (LE) occurs due to the disruption of lymphatic circulation. Lymphatic fluid accumulation in subcutaneous tissues induces adipocyte proliferation. Obesity is an important risk factor for the occurrence and deterioration of LE. Although the relationship between LE and subcutaneous adipose tissue increase has been reported clinically, their pathophysiological relationship remains unknown. Thus, we aimed to verify whether subcutaneous adipose tissue increase is involved in the pathophysiology of secondary LE. Methods and Results: The hindlimb model of secondary LE was created using male Sprague-Dawley rats (control and LE groups; n = 5 each). Skin samples were obtained on postoperative day 168. Histological examination and quantitative real-time polymerase chain reaction analysis of inflammatory adipokines, tumor necrosis factor-alpha (Tnf-α), C-C chemokine ligand 2 (Ccl2), and interleukin-6 (Il-6) were performed. Limb volume and subcutaneous adipose tissues significantly increased in the LE group compared with those in the control. Macrophages aggregated in the augmented adipose tissues, around the adipocytes, and formed crown-like structures (CLSs). The number of CLSs significantly increased in the LE group. These macrophages expressed transforming growth factor-beta 1 (TGF-ß1). Inflammatory adipokine secretion was not observed. Although Il-6 expression increased in the LE group, IL-6 was expressed in subcutaneous myofibroblasts but not in subcutaneous adipocytes. Conclusion: As TGF-ß1 derived from subcutaneous myofibroblasts is involved in skin fibrosis during LE, TGF-ß1 derived from adipose tissues may also play a similar role. Drug treatment for subcutaneous adipose tissue reduction may improve the skin condition in secondary LE and may be a new therapeutic strategy.

Comparison of the postoperative changes in trunk and lower extremity muscle activities between patients with adult spinal deformity and age-matched controls using surface electromyography.

STUDY DESIGN: A prospective study. OBJECTIVE: To investigate the paravertebral and lower extremity muscle activities using surface electromyography (S-EMG) in patients with adult spinal deformity (ASD) comparing with those of age-matched controls. Although the paravertebral muscle is greatly involved in ASD pathology, little is known about the contribution of lower extremity muscle on maintaining standing posture. METHODS: Fourteen patients with ASD (1 man, 13 women; mean age, 67.1 years) who underwent corrective fusion surgery with at least 2 years of follow-up and age-matched controls (1 men, 7 women; mean age, 69.3 years) were enrolled. The muscle activities of the thoracic and lumbar erector spinae (TES and LES), external oblique (EO), gluteus maximus (GM), rectus femoris (RF), and biceps femoris (BF) were recorded in the upright and anterior flexion positions using S-EMG pre-operatively and 1 year post-operatively. RESULTS: Compared with controls, patients showed a significantly higher muscle activity in the LES and BF at rest in a standing position. After corrective fusion surgery, the muscle activity of LES decreased and that of RF increased (p < 0.05), and the changes reached the level of the controls. When the posture changed from upright to anterior flexion, the controls showed increased muscle activity of the BF, whereas the patients showed decreased muscle activity of the TES and RF and increased muscle activity of the BF. Post-operatively, muscle activity of the TES, LES, GM, and BF increased and that of the RF decreased. CONCLUSIONS: ASD patients required a higher activity of the lower extremity and trunk muscles to maintain a standing position compared to the age-matched controls. Significant increase of the GM, BF, and TES muscle activities during anterior bending suggest the presence of mechanical stress concentration caused by fixed lumbar spine. LEVEL OF EVIDENCE: Level III.

Effects of exercise in patients with connective tissue disease receiving high-dose glucocorticoids: A pilot prospective cohort study.

PURPOSE: High doses of glucocorticoids induce skeletal muscle weakness. The aim of this study was to evaluate the effects of exercise therapy on skeletal muscle strength, mass, and exercise capacity in patients with connective tissue disease treated with high doses of glucocorticoids. METHODS: This prospective, observational, single-center, cohort study included 35 patients aged ≥ 15 years diagnosed with connective tissue disease who received high-dose glucocorticoids and physical training. Exercise therapy, including moderate aerobic and strength training, was performed five times a week. Knee extension strength, skeletal muscle mass, anaerobic threshold, and peak oxygen consumption were measured at the beginning of exercise therapy and at discharge. RESULTS: After 6 weeks of aerobic and strength exercises, skeletal muscle mass significantly decreased by 5.5%, right knee extension decreased by 11.6%, and left knee extension decreased by 9.7%. The anaerobic threshold and peak oxygen consumption significantly increased by 13.0% and 9.0%, respectively. The increase in glucocorticoid dose was inversely correlated with changes in knee extension strength. CONCLUSION: In patients with connective tissue disease being treated with high-dose glucocorticoids, exercise therapy might attenuate the decrease in skeletal muscle mass and strength and increase the anaerobic threshold and peak oxygen consumption, thus moderating the side effects of high-dose glucocorticoid treatment. Trial registration The trial is registered with UMIN (University Hospital Medical Information Network), ID number UMIN000038836.

Impact of community pharmacist-led intensive education on the control of serum phosphate levels in haemodialysis patients.

Background Administration of phosphate binders can decrease serum phosphate levels and improve the prognosis of patients on dialysis. However, patients are often non-adherent to phosphate binder medication. Although community pharmacist-led education could be effective in the maintenance of adherence to phosphate binder medication, its impact has not been evaluated. Objective We aimed to evaluate the impact of community pharmacist-led intensive education focusing on phosphate binders for patients receiving haemodialysis. Setting The study comprising three phases (baseline phase, intervention phase, and follow-up phase) was conducted at the Yamauchi Pharmacy, Japan. Method Six pharmacists provided intensive education focusing on phosphate binders to patients receiving haemodialysis. As intensive education, a sheet containing checks for the remaining phosphate binders and information advising the patients on the use of the drugs was issued. Using the check sheet filled in by the patient, the pharmacists repeatedly provided education appropriate to the individual patient's medication status and level of understanding to encourage the correct use of phosphate binders for 8 weeks (intervention phase). We investigated their serum phosphate levels from their medical records from 2 months before the start of intensive education (baseline phase) to 8 months after the end of the education (follow-up phase). Main outcome measure Serum phosphate levels in patients receiving haemodialysis after intensive education by community pharmacists. Results Fifty patients were enrolled in this study. During the intervention phase, serum phosphate levels in the patients with high and the highest serum phosphate level (6-7 mg/dL and ≥ 7 mg/dL, respectively) significantly decreased by 6.9% (P = 0.007) and 10.9% (P = 0.034), respectively. The levels remained below the baseline value throughout the follow-up phase in patients with the highest serum phosphate level. Conclusion Community pharmacist-led education focusing on phosphate binders affects short- and long-term management of serum phosphate levels in patients receiving haemodialysis, especially the patients whose levels were initially high.

Transient Laterality of Cerebral Oxygenation Changes in Response to Head-of-Bed Manipulation in Acute Ischemic Stroke.

BACKGROUND: Cerebral oxygenation monitoring provides important information for optimizing individualized management in patients with acute ischemic stroke (AIS). Although changes in cerebral oxygenation are known to occur in response to head-of-bed (HOB) elevation within 72 h after onset, changes in cerebral oxygenation during stroke recovery are unclear. We compared changes in total- (tHb), oxygenated- (HbO2), and deoxygenated-hemoglobin (deoxyHb) concentrations in response to HOB manipulation between the timeframes within 72 h and 7-10 days after AIS onset. METHODS: We measured forehead ΔtHb, ΔHbO2, and ΔdeoxyHb in response to HOB elevation (30°) within 72 h (first measurement) and 7-10 days (second measurement) after AIS onset using time-resolved near-infrared spectroscopy. RESULTS: We enrolled 30 participants (mean age 72.8 ± 11.3 years; 13 women) with a first AIS. There were no significant differences in ΔtHb, ΔHbO2, or ΔdeoxyHb measurements on the infarct or contra-infarct side. At the first measurement, ΔtHb, ΔHbO2, and ΔdeoxyHb measured on the contra-infarct side did not correlate with those measured on the infarct side: ΔtHb (r = 0.114, p = 0.539); ΔHbO2 (r = 0.143, p = 0.440); ΔdeoxyHb (r = 0.227, p = 0.221). Notably, at the second measurement, correlation coefficients of ΔtHb and ΔHbO2 between the contra-infarct and infarct sides were statistically significant: ΔtHb (r = 0.491, p = 0.008); ΔHbO2 (r = 0.479, p = 0.010); ΔdeoxyHb (r = 0.358, p = 0.054). CONCLUSION: Although changes in cerebral oxygenation in response to HOB elevation had a laterality difference between hemispheres within 72 h of AIS onset, the difference had decreased, at least partially, 7-10 days after AIS onset.

Effects of combination of whey protein intake and rehabilitation on muscle strength and daily movements in patients with hip fracture in the early postoperative period.

BACKGROUND & AIMS: Elderly patients can be at risk of protein catabolism and malnutrition in the early postoperative period. Whey protein includes most essential amino acids and stimulates the synthesis of muscle protein. The purpose of this study was to investigate the effect of resistance training in combination with whey protein intake in the early postoperative period. METHODS: We randomized patients to a whey protein group or a control group. The former group received 32.2 g of whey protein pre- and post-rehabilitation in the early postoperative period for two weeks. Outcomes were knee extension strength on either side by Biodex 4.0, and the ability of transfer, walking, toilet use and stair use by the Barthel Index (BI). We performed initial and final assessments in the second and tenth rehabilitation sessions. RESULTS: A total of 38 patients were recruited: 20 in the whey protein group and 18 in the control group. Participants in the whey protein group showed significantly greater improvement in knee extension strength in the operated limb compared with the control group (F = 6.11, P = 0.02). The non-operated limb also showed a similar tendency (F = 3.51, P = 0.07). The abilities of transfer, walking and toilet use showed greater improvements in the whey protein group than in the control group by BI (P < 0.05). CONCLUSION: The combination of whey protein intake and rehabilitation for two weeks in the early postoperative period has a beneficial effect on knee extension strength in both lower limbs and BI (transfer, walking and toilet use) scores in patients with hip fracture.

Effects of home-based interval walking training on thigh muscle strength and aerobic capacity in female total hip arthroplasty patients: a randomized, controlled pilot study.

UNLABELLED: Due to the reduced physical activity of patients who have undergone total hip arthroplasty (THA), there are no home-based exercise training regimens for preventing muscle atrophy and aerobic capacity impairment in these patients. We examined whether interval walking training (IWT) could prevented these issues. Twenty-eight female patients (∼60 years of age) who had undergone THA more than 2 months prior were randomly divided into IWT (n = 14) and control (CNT, n = 14) groups. The IWT subjects trained at a target of 60 min of fast walking at >70% peak aerobic capacity for walking (VO2peak) per wk for 12 wk, while those in the CNT maintained their previous sedentary life during the same period. We measured the energy expenditure of the daily physical activity, except during sleeping and bathing, every minute and every day during the intervention. We also measured the isometric knee extension (FEXT) and flexion (FFLX) forces, VO2peak, and anaerobic threshold during the graded cycling exercise (VO2AT) before and after the intervention. All subjects, except for one in IWT, completed the protocol. FFLX increased by 23% on the operated side (P = 0.003) and 14% on the non-operated side of IWT (P = 0.006), while it only increased on the operated side of CNT (P = 0.03). The VO2peak and VO2AT in IWT increased by 8% (P = 0.08) and 13% (P = 0.002), respectively, and these changes were significantly higher in the IWT than in CNT group (both, P<0.05). In conclusion, IWT might be an effective home-based training regimen for preventing the muscle atrophy from reduced daily physical activity in THA patients. TRIAL REGISTRATION: UMIN-CTR UMIN000013172.

Effects of peripheral and spinal κ-opioid receptor stimulation on the exercise pressor reflex in decerebrate rats.

The exercise pressor reflex is greater in rats with ligated femoral arteries than it is in rats with freely perfused femoral arteries. The exaggerated reflex in rats with ligated arteries is attenuated by stimulation of µ-opioid and δ-opioid receptors on the peripheral endings of thin-fiber muscle afferents. The effect of stimulation of κ-opioid receptors on the exercise pressor reflex is unknown. We tested the hypothesis that stimulation of κ-opioid receptors attenuates the exercise pressor reflex in rats with ligated, but not freely perfused, femoral arteries. The pressor responses to static contraction were compared before and after femoral arterial or intrathecal injection of the κ-opioid receptor agonist U62066 (1, 10, and 100 µg). Femoral arterial injection of U62066 did not attenuate the pressor responses to contraction in either group of rats. Likewise, intrathecal injection of U62066 did not attenuate the pressor response to contraction in rats with freely perfused femoral arteries. In contrast, intrathecal injection of 10 and 100 µg of U62066 attenuated the pressor response to contraction in rats with ligated femoral arteries, an effect that was blocked by prior intrathecal injection of the κ-opioid receptor antagonist nor-binaltorphimine. In rats with ligated femoral arteries, the pressor response to stimulation of peripheral chemoreceptors by sodium cyanide was not changed by intrathecal U62066 injections, indicating that these injections had no direct effect on the sympathetic outflow. We conclude that stimulation of spinal, but not peripheral, κ-opioid receptors attenuates the exaggerated exercise pressor reflex in rats with ligated femoral arteries.

Hindlimb venous distention evokes a pressor reflex in decerebrated rats.

The distention of small vessels caused by an increase in blood flow to dynamically exercising muscles has been proposed as a stimulus that activates the thin fiber (groups III and IV) afferents evoking the exercise pressor reflex. This theory has been supported by evidence obtained from both humans and animals. In decerebrated unanesthetized rats with either freely perfused femoral arteries or arteries that were ligated 3 days before the experiment, we attempted to provide evidence in support of this theory by measuring arterial pressure, heart rate, and renal sympathetic nerve discharge while retrogradely injecting Ringer's solution in increasing volumes into the femoral vein just as it excited the triceps surae muscles. We found that the pressor response to injection was directly proportional to the volume injected. Retrograde injection of volumes up to and including 1 mL had no significant effect on either heart rate or renal sympathetic nerve activity. Cyclooxygenase blockade with indomethacin attenuated the reflex pressor response to retrograde injection in both groups of rats. In contrast, gadolinium, which blocks mechanogated channels, attenuated the reflex pressor response to retrograde injection in the "ligated rats," but had no effect on the response in "freely perfused" rats. Our findings are consistent with the possibility that distension of small vessels within exercising skeletal muscle can serve as a stimulus to the thin fiber afferents evoking the exercise pressor reflex.

Purinergic 2X receptors play a role in evoking the exercise pressor reflex in rats with peripheral artery insufficiency.

Purinergic 2X (P2X) receptors on the endings of thin fiber afferents have been shown to play a role in evoking the exercise pressor reflex in cats. In this study, we attempted to extend this finding to decerebrated, unanesthetized rats whose femoral arteries were either freely perfused or were ligated 72 h before the start of the experiment. We first established that our dose of pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS; 10 mg/kg), a P2X receptor antagonist, attenuated the pressor response to α,ß-methylene ATP (10 µg/kg), a P2X receptor agonist. We then compared the exercise pressor reflex before and after infusing PPADS into the arterial supply of the hindlimb muscles that were statically contracted. In rats with freely perfused femoral arteries, the peak pressor responses to contraction were not significantly attenuated by PPADS (before PPADS: 19 ± 2 mmHg, 13 min after PPADS: 17 ± 2 mmHg, and 25 min after PPADS: 17 ± 3 mmHg). Likewise, the cardioaccelerator and renal sympathetic nerve responses were not significantly attenuated. In contrast, we found that in rats whose femoral arteries were ligated PPADS significantly attenuated the peak pressor responses to contraction (before PPADS: 37 ± 5 mmHg, 13 min after PPADS: 27 ± 6 mmHg, and 25 min after PPADS: 25 ± 5 mmHg; P < 0.05). Heart rate was not significantly attenuated, but renal SNA was at certain time points over the 30-s contraction period. We conclude that P2X receptors play a substantial role in evoking the exercise pressor reflex in rats whose femoral arteries were ligated but play only a minimal role in evoking the reflex in rats whose femoral arteries were freely perfused.

Increased dietary salt intake enhances the exercise pressor reflex.

Increased dietary salt in rats has been shown to sensitize central sympathetic circuits and enhance sympathetic responses to several stressors, including hyperinsulinemia, intracerebroventricular injection of angiotensin, and electrical stimulation of sciatic nerve afferents. These findings prompted us to test the hypothesis that increased dietary salt enhanced the exercise pressor reflex. Male Sprague-Dawley rats were fed 0.1% (low) or 4.0% (high) NaCl chow for 2 to 3 wk. On the day of the experiment, the rats were decerebrated, and the hind limb muscles were statically contracted for 30 s by electrically stimulating the cut peripheral ends of the L4 and L5 ventral roots. We found that contraction produced a significantly greater increase in mean arterial pressure of rats fed 4.0% (n = 26) vs. 0.1% (n = 22) NaCl (24 ± 2 vs. 15 ± 2 mmHg, respectively; P < 0.05). Baseline mean arterial pressure was not different between groups (0.1%, 77 ± 4 vs. 4.0% NaCl, 80 ± 3 mmHg). Likewise, the tension time indexes were not different between the two groups (P = 0.42). Section of the L4 and L5 dorsal roots greatly attenuated both the pressor and cardioaccelerator responses to contraction in both groups of rats, an effect showing that the responses were reflex in origin. Finally, electrical stimulation of the lumbar sympathetic chain produced similar increases in mean arterial pressure and decreases in femoral arterial blood flow and conductance between rats fed 0.1% vs. 4.0% NaCl diets. We conclude that increased dietary salt enhances the exercise pressor reflex.

Blockade of B2 receptors attenuates the responses of group III afferents to static contraction.

Recent evidence has been presented demonstrating that group III mechanoreceptors comprise an important part of the sensory arm of the exercise pressor reflex, which in turn functions to increase arterial blood flow to contracting skeletal muscles. Although group III afferents are stimulated by mechanical distortion of their receptive fields, they are also stimulated by bradykinin, which is produced by skeletal muscle when it contracts. Moreover, blockade of B (bradykinin)2 receptors has been shown to decrease the magnitude of the exercise pressor reflex. Nevertheless, the effect of blockade of B2 receptors on responses of group III afferents to contraction is not known. We therefore determined the effect of B2 receptor blockade with HOE 140 (40µg/kg) on the responses to both static and intermittent contraction of group III afferents with endings in the triceps surae muscle of decerebrated unanesthetized cats. We found that HOE 140 significantly attenuated (P=0.04) the responses of 14 group III afferents to static contraction, but did not significantly attenuate (P=0.16) the responses of 16 group III afferents to intermittent contraction. The attenuation induced by HOE 140 was present throughout the static contraction period, and led us to speculate that blockade of B2 receptors on the endings of group III afferents decreased their sensitivity to mechanical events occurring in the working muscles.