Hemorrhagic sympathoinhibition mediated through the periaqueductal gray in the rat.
In response to hemorrhage in the anesthetized rat, an initial renal sympathoexcitation is followed by profound sympathoinhibition and hypotension with increasing blood loss. Microinjection of the gamma-aminobutyric acid(A) agonist muscimol to block neurotransmission through the sympathoinhibitory region of the ventrolateral periaqueductal gray matter (vlPAG) did not alter resting sympathetic nerve activity or blood pressure. However, the response to hemorrhage was converted to a maintained renal sympathoexcitation with a delayed and attenuated accompanying hypotension. These data indicate that neurons in the vlPAG mediate the sympathetic and cardiovascular responses to severe hemorrhage.
Dean
Caron
C
Department of Anesthesiology/151, Medical College of Wisconsin and the Zablocki Department of Veterans Affairs Medical Center, Milwaukee, WI 53295, USA. cdean@mcw.edu
D000818:Animals; D001794:Blood Pressure; D018755:GABA Agonists / Q000494:pharmacology; D006470:Hemorrhage / Q000503:physiopathology*; D007022:Hypotension / Q000503:physiopathology; D007668:Kidney / Q000294:innervation; D009118:Muscimol / Q000494:pharmacology; D009433:Neural Inhibition / Q000502:physiology*; D010487:Periaqueductal Gray / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D013564:Sympathetic Nervous System / Q000502:physiology*
D018755:GABA Agonists; D009118:Muscimol