Brain alpha 2-adrenergic receptor binding during incomplete cerebral ischemia in the rat.
alpha 2-Adrenergic agonists decrease sympathetic activity and improve outcome from brain ischemia. We evaluated whether changes in alpha 2-adrenergic receptor binding activity may be important in the sympathetic depressant and cerebral protective effects of halothane (1.1% inspired) or isoflurane (1.4% inspired) compared to fentanyl/nitrous oxide (N2O) anesthesia. Brain alpha 2-adrenergic receptor binding was measured using [3H]-clonidine in each of four treatment conditions: 1, unanesthetized; 2, anesthetized (fentanyl/N2O, halothane, or isoflurane): 3, anesthetized with ischemia; 4, after 4 h recovery from ischemia. Ischemia was produced by right carotid artery ligation combined with hemorrhagic hypotension to 30 mm Hg for 30 min. Both halothane and isoflurane decreased alpha 2-adrenergic receptor density 20% compared to unanesthetized values (P < 0.01). This decrease was attenuated in ischemic tissue. There were no consistent changes in receptor affinity. These results suggest that inhaled anesthetics decrease the number of alpha 2-adrenergic receptors. This decrease appears to be unrelated to plasma catecholamine concentrations but may be influenced by the degree of ischemia.
Department of Anesthesiology, University of Illinois, Chicago.
W E
WE
Hoffman
P
P
Lingamneni
R
R
Minshall
D J
DJ
Miletich
R F
RF
Albrecht
D000769:Anesthesia, Inhalation; D000771:Anesthesia, Intravenous; D000818:Animals; D001794:Blood Pressure; D001921:Brain / Q000378:metabolism*; D002545:Brain Ischemia / Q000378:metabolism / Q000503:physiopathology*; D002245:Carbon Dioxide / Q000097:blood; D005283:Fentanyl; D006221:Halothane; D006863:Hydrogen-Ion Concentration; D007530:Isoflurane; D008297:Male; D009609:Nitrous Oxide; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D051381:Rats; D017207:Rats, Sprague-Dawley; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*
D011942:Receptors, Adrenergic, alpha; D002245:Carbon Dioxide; D007530:Isoflurane; D009609:Nitrous Oxide; D010100:Oxygen; D005283:Fentanyl; D006221:Halothane