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Patterns of hemodynamic responses associated with central activation of coronary vasoconstriction
L F Jones1, D D Gutterman, M J Brody
1Department of Pharmacology, University of Iowa, Iowa City 52242.
Insights
Electrical stimulation of specific brain areas in cats caused coronary vasoconstriction, a key part of the defense reaction. This response involved changes in blood flow and pressure, linking coronary artery constriction to the body's fight-or-flight system.
Area of Science:
- Neuroscience
- Cardiovascular Physiology
Background:
- Previous research identified central nervous system sites triggering coronary vasoconstriction via electrical stimulation.
- The current study investigates the hemodynamic response patterns linked to activating these coronary vasoconstrictor pathways.
Purpose of the Study:
- To determine if specific hemodynamic response patterns correlate with the activation of coronary vasoconstrictor pathways in the hypothalamus, pons, and medulla.
- To elucidate the role of these central pathways in mediating coronary vasoconstriction as part of a broader physiological response.
Main Methods:
- Anesthetized cats underwent instrumentation for monitoring arterial pressure, heart rate, and blood flow velocities in coronary, femoral, renal, and mesenteric arteries.
- Electrical stimulation was applied to the anterior hypothalamus (AHA), parabrachial nucleus (PBN), and rostral ventrolateral medulla (RVLM) after vagotomy and atenolol administration.
Main Results:
- Electrical stimulation of AHA, PBN, and RVLM induced decreased coronary blood flow.
- This coronary vasoconstriction was consistently associated with the cardiovascular components of the defense reaction, including hindquarter vasodilation, increased renal and mesenteric vascular resistance, and a pressor response.
- The RVLM stimulation showed no change in renal vascular resistance, differentiating it from other stimulated sites.
Conclusions:
- Coronary vasoconstriction is a frequent and integral component of the defense reaction.
- Specific central nervous system sites, including the hypothalamus and brainstem, mediate coronary vasoconstriction as part of a coordinated physiological response.
Abstract:
Previous studies in our laboratory have identified several central sites from which coronary vasoconstriction can be elicited by electrical stimulation. The present study was conducted to determine if specific patterns of hemodynamic responses are associated with activation of the coronary vasoconstrictor pathway in the hypothalamus, pons, and medulla. Cats anesthetized with chloralose were instrumented for recording arterial pressure, heart rate, and coronary, femoral, renal, and mesenteric blood flow velocities. After vagotomy and atenolol (1 mg/kg iv), anterior hypothalamus (AHA), parabrachial nucleus (PBN), a site very close to the ventral surface of the pons lateral to the pyramidal tract, and rostral ventrolateral medulla (RVLM) were stimulated electrically. Stimulation produced a decrease in coronary blood flow that was associated with all of the cardiovascular components of the defense reaction, an integrated response that included a decrease in hindquarter vascular resistance (blocked by methyl atropine), increases in renal and mesenteric vascular resistances, and a pressor response, except no change in renal vascular resistance from RVLM. Different patterns of hemodynamic responses were obtained from sites outside the coronary vasoconstrictor areas. From these results we conclude that coronary vasoconstriction is a frequent component of the defense reaction.