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Cardiac sympathetic nerve activity and adrenal sympathetic nerve activity: Changes in hemorrhagic hypotension
J Mol
2
14
Cell
Cardiol21
(Supplement
II) (1989)
ARTERIAL VERSUS VENOUS PLASMA EPINEPHRINE ABSORPTION FOLLOWING EPINEPHRINE-IMPREGNATED DENTAL RETRACTION CORD OR EPINEPHRINE INFUSION. G. L. Todd, C. Reese, D. H. Sbaw, R.F. Krejci. Departments of Anatomy and Oral Biology, University of Nebraska Medical Center, Omaha, NE. The use of epinephrine-impregnated retraction cord (EPI-Cord) in restorative dentistry is controversial because of the reported inconsistencies of epinephrine (EPI) absorption and patient safety. Plasma catecholamine levels and cardiovascular responses were measured during a simulated dental procedure for 60 minutes in anesthetized adult mongrel dogs. Common carotid arterial and external jugular venous blood samples along with recordings of hemodynamic parameters were taken before and at intervals after placement of EPI-Cord, unmedicated cord or EPI infusions (0.5 ug/kg/min). Heart tissue was processed for routine histology. EPI-Cord produced a 5.8 fold increase in arterial plasma EPI levels by 30 min while EPI infusion produced an increase of 18.4 fold. At 60 min. the venous plasma EPI levels had increased 38 fold in the EPI-Cord group and only 10.7 fold in the EPI-infused group. There were modest increases in heart rate and blood pressure, but the only significant increase was in myocardial contractility (dP/dt). Despite significant increases in plasma EPI concentrations, there was no evidence of necrotic damage to the myocardium. While healthy animals appear to tolerate these EPI increases, further research needs to be done to determine if certain patient subpopulations are at increased risk of serious complications.
215
~~~~~~"'-1""""'" ENHANCEMENT OF CONTRACTILE FUNCTION IN IRSDALATED PERFUSED RAT : EFFECT OF TUBOCIJRARE AND CALCIUM CONCENTRATION. Fenton and J.G. Dobson. Jr. Univ. of Massachusetts Med. Sch., Worcester, MA 01655 USA. Nicotine in the heart augments the developed left ventricular pressure (LVP) and the rates of pressure development (+dP/dt) and relaxation (-dP/dt) independently of B-adrenergic or muscarinic receptor stimulation and changes in CAMP. This study investigated the mechanism by which nicotine elicits a positive inotropic response. Rat hearts were constant-flow perfused with physiological saline (2.5 mM Ca2+; lo-6M propranolol; 10 ml/min) and paced at 330/min. The contractile response for 6 x lo-6M to lo-3M nicotine consisted of a peak increase (P) at 15 set which declined to a maintained elevated value (M) at 1 min. With lo-3M nicotine LVP values for P and M were increased above control (50.7 n-mHg) by 39.5 and 22.3 mmHg, respectively. Reducing the saline Ca2+ to 1 mM significantly reduced the control value by 39% and the P response by 41%. The M response was not significantly Raising the Ca2+ to 4 mM did not further potentiate the P or M decreased. responses. Similar results were observed with +_dP/dt. At 2.5 mM Ca2+, 30 HM d-tubocurarine, a nicotinic receptor antagonist, reduced the lo-4M nicotine M response by 58%, but not the P response. These results sug est that the cardiac response to nicotine depends upon an enhanced influx of Ca 9 + from a superficial extracellular pool and a tubocurarine-sensitive release of Ca2+ from intracellular stores. (Supported by Smokeless Tobacco Research. Inc. Grant #0169 01).
216
CARDIAC SYMPATHETIC NERVE ACTIVITY AND ADRENAL SYMPATHETIC NERVE ACTIVITY: CHANGES IN HEMORRHAGIC HYPOTENSION. H. Toqashi, M. Yoshioka, H. Saito, M. Matsumoto and M. First Department of Pharmacology, Tochihara. Hokkaido University School of Medicine, Sapporo, japan. The regional responses of cardiac and adrenal sympathetic nerve to acute hemorrhagic hypotension were studied in alpha-chloralose-urethane anesthetized rats. In order to clarify the contributions of afferent pathways from barereceptors and cardiopulmonary receptors, bilateral vaqotomy was also performed. Blood was withdrawn at a volume of 2, 5 and 10 ml/kg from left femoral artery into a heparinized syringe, and was kept for 10 min. Hemorrhage produced a volume dependent decrease in arterial blood pressure and heart rate, accompanied with a The cardiac nerve activity showed a rapid decrease in right atria1 pressure. decrease associated with the volume of bleeding. On the other hand, the adrenal Bilateral vagotomy nerve activity showed a gradual increase after hemorrhage. attenuated the decrease in heart rate and cardiac nerve activity, and significantly attenuated the increase in adrenal nerve activity. These findings suggest that acute hemorrhagic hypotension produced the dissociation of cardiac and adrenal It was also demonstrated that vaqal nerves are sympathetic nerve activities. possibly involved in hemorrhage induced dissociation of sympathetic nerve activities.
S.72
2
14
Cell
Cardiol21
(Supplement
II) (1989)
ARTERIAL VERSUS VENOUS PLASMA EPINEPHRINE ABSORPTION FOLLOWING EPINEPHRINE-IMPREGNATED DENTAL RETRACTION CORD OR EPINEPHRINE INFUSION. G. L. Todd, C. Reese, D. H. Sbaw, R.F. Krejci. Departments of Anatomy and Oral Biology, University of Nebraska Medical Center, Omaha, NE. The use of epinephrine-impregnated retraction cord (EPI-Cord) in restorative dentistry is controversial because of the reported inconsistencies of epinephrine (EPI) absorption and patient safety. Plasma catecholamine levels and cardiovascular responses were measured during a simulated dental procedure for 60 minutes in anesthetized adult mongrel dogs. Common carotid arterial and external jugular venous blood samples along with recordings of hemodynamic parameters were taken before and at intervals after placement of EPI-Cord, unmedicated cord or EPI infusions (0.5 ug/kg/min). Heart tissue was processed for routine histology. EPI-Cord produced a 5.8 fold increase in arterial plasma EPI levels by 30 min while EPI infusion produced an increase of 18.4 fold. At 60 min. the venous plasma EPI levels had increased 38 fold in the EPI-Cord group and only 10.7 fold in the EPI-infused group. There were modest increases in heart rate and blood pressure, but the only significant increase was in myocardial contractility (dP/dt). Despite significant increases in plasma EPI concentrations, there was no evidence of necrotic damage to the myocardium. While healthy animals appear to tolerate these EPI increases, further research needs to be done to determine if certain patient subpopulations are at increased risk of serious complications.
215
~~~~~~"'-1""""'" ENHANCEMENT OF CONTRACTILE FUNCTION IN IRSDALATED PERFUSED RAT : EFFECT OF TUBOCIJRARE AND CALCIUM CONCENTRATION. Fenton and J.G. Dobson. Jr. Univ. of Massachusetts Med. Sch., Worcester, MA 01655 USA. Nicotine in the heart augments the developed left ventricular pressure (LVP) and the rates of pressure development (+dP/dt) and relaxation (-dP/dt) independently of B-adrenergic or muscarinic receptor stimulation and changes in CAMP. This study investigated the mechanism by which nicotine elicits a positive inotropic response. Rat hearts were constant-flow perfused with physiological saline (2.5 mM Ca2+; lo-6M propranolol; 10 ml/min) and paced at 330/min. The contractile response for 6 x lo-6M to lo-3M nicotine consisted of a peak increase (P) at 15 set which declined to a maintained elevated value (M) at 1 min. With lo-3M nicotine LVP values for P and M were increased above control (50.7 n-mHg) by 39.5 and 22.3 mmHg, respectively. Reducing the saline Ca2+ to 1 mM significantly reduced the control value by 39% and the P response by 41%. The M response was not significantly Raising the Ca2+ to 4 mM did not further potentiate the P or M decreased. responses. Similar results were observed with +_dP/dt. At 2.5 mM Ca2+, 30 HM d-tubocurarine, a nicotinic receptor antagonist, reduced the lo-4M nicotine M response by 58%, but not the P response. These results sug est that the cardiac response to nicotine depends upon an enhanced influx of Ca 9 + from a superficial extracellular pool and a tubocurarine-sensitive release of Ca2+ from intracellular stores. (Supported by Smokeless Tobacco Research. Inc. Grant #0169 01).
216
CARDIAC SYMPATHETIC NERVE ACTIVITY AND ADRENAL SYMPATHETIC NERVE ACTIVITY: CHANGES IN HEMORRHAGIC HYPOTENSION. H. Toqashi, M. Yoshioka, H. Saito, M. Matsumoto and M. First Department of Pharmacology, Tochihara. Hokkaido University School of Medicine, Sapporo, japan. The regional responses of cardiac and adrenal sympathetic nerve to acute hemorrhagic hypotension were studied in alpha-chloralose-urethane anesthetized rats. In order to clarify the contributions of afferent pathways from barereceptors and cardiopulmonary receptors, bilateral vaqotomy was also performed. Blood was withdrawn at a volume of 2, 5 and 10 ml/kg from left femoral artery into a heparinized syringe, and was kept for 10 min. Hemorrhage produced a volume dependent decrease in arterial blood pressure and heart rate, accompanied with a The cardiac nerve activity showed a rapid decrease in right atria1 pressure. decrease associated with the volume of bleeding. On the other hand, the adrenal Bilateral vagotomy nerve activity showed a gradual increase after hemorrhage. attenuated the decrease in heart rate and cardiac nerve activity, and significantly attenuated the increase in adrenal nerve activity. These findings suggest that acute hemorrhagic hypotension produced the dissociation of cardiac and adrenal It was also demonstrated that vaqal nerves are sympathetic nerve activities. possibly involved in hemorrhage induced dissociation of sympathetic nerve activities.
S.72