DAILY SPONTANEOUS RUNNING (DSR) DID NOT ALTER AORTIC BARORECEPTOR REACTIVITY TO CHANGES IN ARTERIAL-PRESSURE
Biochemistry & Molecular Biology; Cell Biology; Life Sciences & Biomedicine - Other; Topics
Chen C Y; DiCarlo S E; Scislo T
Faseb Journal
1994
1994-03
Journal Article or Conference Abstract Publication
n/a
Arterial baroreflex regulation of lumbar nerve activity: Influence of gender and daily exercise
Biochemistry & Molecular Biology; Cell Biology; Life Sciences & Biomedicine - Other; Topics
Chen C Y; DiCarlo S E
Faseb Journal
1996
1996-03
Journal Article or Conference Abstract Publication
n/a
ENHANCED CARDIAC RECEPTOR REGULATION OF HEART-RATE DURING EXERCISE
Biochemistry & Molecular Biology; Cell Biology; Life Sciences & Biomedicine - Other; Topics
Chen C Y; Collins H L; DiCarlo S E
Faseb Journal
1993
1993-02
Journal Article or Conference Abstract Publication
n/a
Enhanced cardiopulmonary reflex inhibition of heart rate during exercise.
Animals; Rats; Analysis of Variance; Physical Stimulation; Blood Pressure/drug effects/physiology; Rest; Biguanides/pharmacology; Blood Volume; Bradycardia/physiopathology; Heart Rate/drug effects/*physiology; Heart/drug effects/*physiology; Hypoglycemic Agents/pharmacology; Lung/drug effects/*physiology; Physical Exertion/*physiology; Reflex/drug effects/*physiology; Sympathetic Nervous System/drug effects/physiology; Vagotomy; Vagus Nerve/drug effects/physiology; Neurons; Chemical; Stimulation; Afferent/drug effects/physiology
We tested the hypothesis that the reflex inhibition of heart rate (HR) during mechanical (acute bolus injection of 0.5% and 2% of estimated blood volume) and chemical (phenylbiguanide, PBG, 2.5 and 5 micrograms.kg-1) stimulation of cardiopulmonary receptors would be enhanced during exercise. Rats were instrumented with arterial and venous catheters. The reflex response to mechanical (N = 7) and chemical (N = 8) stimulation of cardiopulmonary receptors was examined at rest and during exercise (6 m.min-1, 10% grade). A two-way analysis of covariance (ANCOVA) with repeated measures was used to test for differences in the reflex regulation of HR at rest vs exercise. HR was used as the covariate because exercise significantly increased baseline HR. There was no significant treatment effect (rest vs exercise) for the reflex inhibition of HR during mechanical stimulation. However, the two-way ANCOVA revealed a significant treatment effect (rest vs exercise) for the reflex inhibition of HR during chemical stimulation. The reflex decreases in HR were enhanced (-delta 23 +/- 8 vs -delta 133 +/- 47 and -delta 208 +/- 40 vs -delta 374 +/- 10 bpm at 2.5 and 5 micrograms.kg-1, respectively). These data suggest that factors associated with exercise enhanced the cardiopulmonary reflex inhibition of heart rate during chemical stimulation.
Chen C Y; DiCarlo S E; Collins H L
Medicine and science in sports and exercise
1995
1995-10
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1249/00005768-199510000-00008" target="_blank" rel="noreferrer noopener">10.1249/00005768-199510000-00008</a>
Vagal afferents reflexly inhibit exercise in conscious rats.
Animals; Rats; Action Potentials/drug effects/physiology; Electromyography; Blood Pressure/drug effects/physiology; Physical Exertion/*physiology; Consciousness; Heart Rate/drug effects/physiology; Afferent Pathways/drug effects/physiology; Biguanides/administration & dosage/*pharmacology; Motor Activity/*drug effects/*physiology; Muscles/drug effects/physiology; Reflex/*drug effects/*physiology; Serotonin Receptor Agonists/administration & dosage/*pharmacology; Vagus Nerve/*drug effects/*physiology; Dose-Response Relationship; Drug; Sprague-Dawley
Activation of vagal afferents reflexly inhibited locomotion induced by stimulation of the mesencephalic locomotor region in decerebrate cats. However, this reflex has not been tested in intact mammals. Therefore, the purpose of this study was to test the hypothesis that vagal afferent stimulation would inhibit somatomotor activity in the intact conscious rat. Six Sprague-Dawley rats were chronically instrumented with carotid arterial and femoral venous catheters and electromyogram (EMG) electrodes inserted into the biceps femoris muscle. Cardiac autonomic efferent blockade [atropine methyl bromide (14 mg.kg-1, i.v.) and metoprolol (14 mg.kg-1, i.v.)] and alpha-adrenergic receptor blockade [phenoxybenzamine (5 mg.kg-1, i.v.)] was achieved to prevent bradycardia and hypotension. Vagal afferents were stimulated (phenyl-biguanide 2.5 and 5.0 micrograms.kg-1 i.v.) during steady state exercise (9.0 m.min-1, 10% grade). Phenyl-biguanide decreased exercise EMG activity 30 +/- 6% and 54 +/- 10% in a dose dependent manner without significantly altering mean arterial pressure or heart rate. We speculate that this reflex may serve as a negative feedback mechanism to indirectly reduce myocardial oxygen demands during exercise.
DiCarlo S E; Collins H L; Chen C Y
Medicine and science in sports and exercise
1994
1994-04
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1249/00005768-199404000-00010" target="_blank" rel="noreferrer noopener">10.1249/00005768-199404000-00010</a>
Daily spontaneous running alters behavioral and neurochemical indexes of nigrostriatal function.
Animal/*physiology; Animals; Behavior; Chromatography; Circadian Rhythm; Corpus Striatum/cytology/*physiology; Dopamine/*metabolism; High Pressure Liquid; In Vitro Techniques; Male; Neuropsychological Tests; Organ Size; Perfusion; Physical Conditioning; Potassium/*metabolism; Psychomotor Performance/*physiology; Random Allocation; Rats; Sprague-Dawley
Behavioral and neurochemical indexes of nigrostriatal dopaminergic function were compared between sedentary control rats (n = 12) and daily spontaneous running (DSR) male rats (n = 10). Nine weeks of DSR did not significantly alter body, heart, pituitary, or testes weights. DSR and control animals did differ in performance on a sensorimotor beam walking task, with DSR rats showing significantly shorter times required to cross the beam (60 +/- 17 vs. 119 +/- 14s; P \textless 0.02) as well as fewer slips off the beam (3.0 +/- 0.8 vs 6.2 +/- 1.1; P \textless 0.05). DSR animals also engaged in significantly greater durations of social investigation than control rats (43 +/- 5 vs 25 +/- 3 s; P \textless 0.01) when tested in a social investigation memory-recognition test. Basal dopamine release rates from superfused corpus striatal tissue fragments of DSR rats were about one-half those obtained from control animals (18 +/- 5 vs. 34 +/- 6 pg.mg-1.min-1; P \textless 0.05), whereas responses of these striatal tissue fragments to a depolarizing concentration of potassium were virtually identical (45 +/- 10 vs. 47 +/- 8 pg.mg-1.min-1). These data indicate that a relatively limited intensity of DSR insufficient to alter cardiovascular function can exert substantial effects on behavioral and neurochemical indicators of nigrostriatal dopaminergic activity.
Dluzen D E; Liu B; Chen C Y; DiCarlo S E
Journal of applied physiology (Bethesda, Md. : 1985)
1995
1995-04
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1152/jappl.1995.78.4.1219" target="_blank" rel="noreferrer noopener">10.1152/jappl.1995.78.4.1219</a>
Daily exercise and gender influence arterial baroreflex regulation of heart rate and nerve activity.
*Physical Conditioning; *Sex Characteristics; Animal; Animals; Arteries/*physiology; Baroreflex/*physiology; Female; Heart Rate/*physiology; Lumbosacral Region; Male; Rats; Rest; Sprague-Dawley; Sympathetic Nervous System/*physiology
The influence of daily spontaneous running (DSR) and gender on the arterial baroreflex regulation of heart rate (HR) and lumbar sympathetic nerve activity (LSNA) was examined in 13 male [7 sedentary (SED) and 6 DSR] and 12 female (6 SED and 6 DSR) Sprague-Dawley rats. After 8-9 wk of DSR or SED control, all animals were chronically instrumented with right femoral venous and left carotid arterial catheters and electrodes around the lumbar sympathetic trunk. DSR resulted in an increase in heart weight-to-body weight ratio (P = 0.001) in male and female rats and resting bradycardia in male rats (P = 0.001). Arterial baroreflex function was examined by ramp increases (1.25 +/- 0.07 mmHg/s) and decreases (1.47 mmHg/s) in arterial pressure. DSR attenuated the arterial baroreflex regulation of LSNA in a similar manner in female and male rats. DSR reduced the range (32 and 29% for female and male rats, respectively), maximum (26 and 21% for female and male rats, respectively), and maximum gain (Gmax; 46 and 17% for female and male rats, respectively). In contrast, there was a gender influence on the arterial baroreflex regulation of HR. For example, SED female rats had a higher Gmax (40%) than SED male rats. Furthermore, DSR altered the arterial baroreflex regulation of HR differently in male and female rats. DSR female rats had a reduced Gmax (38%), range (25%), and maximum (12%), whereas DSR male rats had a reduced maximum (17%) and minimum (23%). These results demonstrate that DSR attenuated the arterial baroreflex regulation of LSNA in a similar manner in female and male rats. In contrast, DSR altered the arterial baroreflex regulation of HR differently in female and male rats.
Chen C Y; DiCarlo S E
The American journal of physiology
1996
1996-11
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1152/ajpheart.1996.271.5.H1840" target="_blank" rel="noreferrer noopener">10.1152/ajpheart.1996.271.5.H1840</a>
Daily spontaneous running attenuated the central gain of the arterial baroreflex.
Animal; Animals; Arteries/*physiology; Baroreflex/*physiology; Brain/*physiology; Female; Male; Motor Activity/*physiology; Physical Conditioning; Rats; Sprague-Dawley
Exercise training attenuates arterial baroreflex function. Mechanisms responsible may include an attenuated aortic baroreceptor reactivity (afferent mechanisms) and/or an attenuated central baroreflex gain. We tested the hypothesis that the aortic baroreceptor reactivity and/or central gain is attenuated by daily spontaneous running (DSR). Eighteen anesthetized Sprague-Dawley rats (11 control and 7 DSR) were tracheotomized and instrumented with femoral venous and right carotid arterial catheters. Electrodes were placed around the left aortic depressor nerve and the lumbar sympathetic trunk. Eight to thirteen weeks of DSR were associated with a 20% increase in heart weight-to-body weight ratio (2.83 +/- 0.04 vs. 3.39 +/- 0.10 g/kg; P \textless 0.001) and resting bradycardia (413 +/- 6 vs. 384 +/- 10 beats/min; P = 0.01). DSR reduced the central gain of the baroreflex regulation of heart rate (0.210 +/- 0.046 vs. 0.005 +/- 0.021 beats.min-1.%-1; P = 0.004) during decreases in arterial pressure. However, the reactivity of aortic baroreceptor afferents and the central gain of the baroreflex control of lumbar sympathetic nerve activity were not different in control and DSR rats. Thus DSR reduced the central gain of the arterial baroreflex regulation of heart rate without changing the reactivity of aortic baroreceptor afferents. We conclude that afferent mechanisms are not responsible for the training-induced reduction in arterial baroreflex function.
Chen C Y; DiCarlo S E; Scislo T J
The American journal of physiology
1995
1995-02
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1152/ajpheart.1995.268.2.H662" target="_blank" rel="noreferrer noopener">10.1152/ajpheart.1995.268.2.H662</a>
Local modulation of adrenergic responses in the hindlimb vasculature of the intact conscious rat.
Adrenergic Agonists/*pharmacology; Animals; Arginine/analogs & derivatives/pharmacology; Cyclooxygenase Inhibitors/pharmacology; Female; Hemodynamics/*drug effects/physiology; Hindlimb/*blood supply/drug effects/metabolism; Indomethacin/pharmacology; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase/antagonists & inhibitors; Rats; Sprague-Dawley
1. Local modulation of adrenergic responses was examined in the hindlimb vasculature of chronically instrumented intact conscious rats. Sprague-Dawley rats (n = 22) were instrumented with a Doppler flow probe around the right common iliac artery, a polyethylene catheter inserted just distal to the flow probe and a left carotid arterial catheter. 2. The effects of various concentrations of the alpha 1-adrenergic receptor agonist phenylephrine (0.005-0.075 microgram kg-1), the alpha 2-adrenergic receptor agonist clonidine (0.1-0.7 microgram kg-1), and the endogenous adrenergic receptor agonist adrenaline (0.02-0.08 microgram kg-1), were investigated under control conditions, and in the presence of the nitric oxide (NO) synthase inhibitor N omega-nitro-L-arginine methyl ester hydrochoride (L-NAME) (NO-X, 0.2 mg kg-1) and the cyclo-oxygenase inhibitor indomethacin (CO-X, 10 mg kg-1). Results were presented as dose-response curves. 3. Heart rate and arterial pressure were not altered by any of the agents because all were locally injected into the hindlimb vasculature and the selected doses were lower than those which elicited systemic responses. 4. Maximal vasoconstrictor responses to phenylephrine were enhanced in the presence of NO-X (50 +/- 6%) and
DiCarlo S E; Patil R D; Collins H L; Chen C Y
The Journal of physiology
1995
1995-06
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1113/jphysiol.1995.sp020771" target="_blank" rel="noreferrer noopener">10.1113/jphysiol.1995.sp020771</a>
Onset of exercise increases lumbar sympathetic nerve activity in rats.
Animal/*physiology; Animals; Blood Pressure; Heart Rate; Lumbar Vertebrae/*innervation; Physical Conditioning; Rats; Sympathetic Nervous System/*physiology
We hypothesized that lumbar sympathetic nerve activity (LSNA) increases at the onset of whole-body dynamic exercise in the rat. To test this hypothesis, we recorded LSNA, heart rate (HR), and arterial pressure (AP) at rest and during a graded exercise test in six adult rats. Rats were instrumented with arterial and venous catheters and recording electrodes around the lumbar sympathetic trunk. Following recovery, each rat ran continuously on a hand-driven or motorized treadmill at 6 m.min-1, 12 m.min-1, and 18 m.min-1 on a 10% grade for approximately 3 min at each workload. Before exercise, mean arterial pressure (MAP), HR, and LSNA averaged 108 +/- 4 mm Hg, 385 +/- 20 bpm, and 100%, respectively. As hypothesized, all variables increased abruptly and dramatically at the onset of treadmill exercise. For example, MAP (117 +/- 5 mm Hg), HR (450 +/- 15 bpm), and LSNA (225 +/- 19%) all increased significantly within the first 25 s of treadmill running at 6 m.min-1. As the exercise continued, there was a progressive increase in HR; however, MAP plateaued at 6 m.min-1 and LSNA plateaued at 12 m.min-1. Since LSNA increased at the onset of whole-body dynamic exercise in the rat, we suggest that the increase in LSNA at the onset of exercise is mediated by a central (feed forward) mechanism.
DiCarlo S E; Chen C Y; Collins H L
Medicine and science in sports and exercise
1996
1996-06
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1097/00005768-199606000-00006" target="_blank" rel="noreferrer noopener">10.1097/00005768-199606000-00006</a>