Medullary pathway of the Bezold-Jarisch reflex in the rat.
The central pathway mediating the Bezold-Jarisch reflex elicited by jugular vein injection of serotonin (5-HT) and phenyl biguanide (PBG) was studied in halothane-anesthetized, paralyzed rats. 5-HT and PBG produced hypotension and inhibition of lumbar sympathetic discharge often preceded by sympathoexcitation. The Bezold-Jarish reflex was blocked by bilateral kynurenic acid (KYN; glutamate antagonist, 1.25 nmol/side) microinjection into the solitary tract nucleus. Bilateral KYN injection into the caudal ventrolateral medulla (5 nmol/side) also blocked the reflex. Bilateral injection of bicuculline methiodide (BIC; 100 pmol/side) into the rostral ventrolateral medulla (RVL) reduced the depressor and sympathoinhibitory components of the reflex and enhanced an excitatory component. Blockade or attenuation of the Bezold-Jarisch reflex was always associated with a concomitant blockade or attenuation of the arterial baroreflex. RVL barosensitive neurons (n = 61) were inhibited (> 60% reduction in firing) by PBG and 5-HT. Iontophoretic application of BIC (n = 11 cells), but not strychnine (glycine antagonist), blocked inhibition of RVL neurons by 5-HT and PBG. The sympathoinhibitory component of the Bezold-Jarisch reflex may use a central pathway similar to that of the arterial baroreflex.
Verberne
A J
AJ
Department of Pharmacology, University of Virginia School of Medicine, Charlottesville 22908.
Guyenet
P G
PG
D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D006329:Heart Conduction System / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D008168:Lung / Q000294:innervation*; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology / Q000502:physiology*; D009424:Nervous System Physiological Phenomena; D009433:Neural Inhibition; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012018:Reflex / Q000502:physiology*