Blood pressure reduction induced by low dose of epinephrine via different routes in rats.
BACKGROUND
Epinephrine was recently shown to induce a hypotension episode. Activation of β₂-adrenoceptors with smooth muscle relaxation may be the underlying mechanism. This study investigated the effects of ICI 118551, a β₂-adrenoceptors antagonist, on epinephrine-induced blood pressure reduction via different administration routes in rats.


METHODS
A total of 144 Sprague Dawley rats were equally randomized into 3 groups (intranasal, intravenous, and intra-arterial administration), each with 4 subgroups: saline + saline, ICI 118551 + saline, saline + epinephrine, and ICI 118551 + epinephrine. All rats were anesthetized while spontaneously breathing. Epinephrine was administered at doses of 5 μg/kg via nose, 0.25 μg/kg via femoral vein, and 0.1 μg/kg via aorta. Mean arterial pressure and heart rate were monitored.


RESULTS
Mean arterial pressure decreased in all 3 saline + epinephrine subgroups after administration (P < 0.05), whereas it did not in other subgroups. Heart rate had no significant change in all subgroups.


CONCLUSIONS
Epinephrine-induced blood pressure reduction can be prevented by ICI 118551 in rats, suggesting that the activation of β₂-adrenoceptors contributes to blood pressure reduction.
*Department of Anesthesiology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing, P. R. China; †Department of Anesthesiology, First Affiliated Hospital of Nanjing Medical University, Nanjing, P. R. China; and ‡Department of Anesthesiology, Shands Hospital, School of Medicine, University of Florida, Gainesville, FL.
Jing
J
Wu
Mu-Huo
MH
Ji
Zhong-Yun
ZY
Wang
Wei
W
Zhu
Jian-Jun
JJ
Yang
Yong G
YG
Peng
D000281:Administration, Intranasal; D058666:Adrenergic beta-2 Receptor Agonists / Q000008:administration & dosage* / Q000009:adverse effects / Q000737:chemistry; D058672:Adrenergic beta-2 Receptor Antagonists / Q000627:therapeutic use; D000818:Animals; D000959:Antihypertensive Agents / Q000008:administration & dosage* / Q000009:adverse effects / Q000037:antagonists & inhibitors; D001013:Aorta, Thoracic; D001794:Blood Pressure / Q000187:drug effects*; D004837:Epinephrine / Q000008:administration & dosage* / Q000009:adverse effects / Q000037:antagonists & inhibitors; D005268:Femoral Vein; D006339:Heart Rate / Q000187:drug effects; D007022:Hypotension / Q000139:chemically induced / Q000517:prevention & control; D007261:Infusions, Intra-Arterial; D007262:Infusions, Intravenous; D008297:Male; D011412:Propanolamines / Q000627:therapeutic use; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D018343:Receptors, Adrenergic, beta-2 / Q000737:chemistry / Q000378:metabolism
D058666:Adrenergic beta-2 Receptor Agonists; D058672:Adrenergic beta-2 Receptor Antagonists; D000959:Antihypertensive Agents; D011412:Propanolamines; D018343:Receptors, Adrenergic, beta-2; C026777:ICI 118551; D004837:Epinephrine