Coronary vasoconstrictor pathway from anterior hypothalamus includes neurons in RVLM.
We have previously identified discrete brain sites [anterior (AHA) and lateral hypothalamus, periaqueductal gray, pontine parabrachial nucleus, lateral reticular formation, and rostral ventrolateral medulla (RVLM)] in the cat, in which electrical or chemical activation produces coronary vasoconstriction. This study examines whether the most rostral (AHA) and caudal (RVLM) of these sites are connected as part of a common pathway mediating coronary vasoconstriction. In chloralose-anesthetized cats, electrical stimulation in the AHA produced maximum increases in arterial pressure (41 +/- 10%) and coronary vascular resistance (28 +/- 9%). Microinjection of lidocaine into the RVLM attenuated the increases in arterial pressure (10 +/- 3%) and coronary vascular resistance (5 +/- 1%) in response to electrical stimulation in the AHA (P < 0.05 vs. before lidocaine). Lidocaine nonspecifically inhibits neural elements in the region. gamma-Aminobutyric acid in the RVLM, which selectively inhibits cell bodies and not fibers passing through the RVLM, attenuated the increase in coronary vascular resistance (38 +/- 8 to 14 +/- 3%; P < 0.05) but not the increase in arterial pressure (87 +/- 12 to 92 +/- 16%) in response to electrical stimulation in the AHA. These data indicate that coronary vasoconstriction in response to electrical stimulation in the AHA requires cell bodies in the RVLM; however, the associated pressor response is mediated by fibers passing through the RVLM. We conclude that a polysynaptic descending pathway that mediates sympathetic coronary vasoconstriction descends from the AHA through a synaptic connection in the RVLM.
Goodson
A R
AR
Department of Internal Medicine, College of Medicine, University of Iowa, Iowa City 52242.
LaMaster
T S
TS
Gutterman
D D
DD
D000818:Animals; D007025:Anterior Hypothalamic Nucleus / Q000502:physiology*; D002415:Cats; D003331:Coronary Vessels / Q000502:physiology*; D004558:Electric Stimulation; D005260:Female; D007267:Injections; D008012:Lidocaine / Q000494:pharmacology; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D014661:Vasoconstriction / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D005680:gamma-Aminobutyric Acid; D008012:Lidocaine