Sympathetic beta-agonists and cochlear blood flow in guinea pigs.
The effects of sympathetic beta-agonists on blood pressure and cochlear blood flow were studied in 15 guinea pigs. Cochlear blood flow was measured by a laser Doppler flowmeter, Periflux PF2 (Perimed, Sweden). Small doses (0.01 and 0.1 microgram/kg) of isoproterenol elevated blood pressure, but larger doses (10 and 50 micrograms/kg) decreased blood pressure. Cochlear blood flow showed a biphasic pattern, in that there was an initial decrease with a subsequent increase. Dobutamine, a beta 1-agonist, elevated blood pressure and increased cochlear blood flow in a dose-dependent manner. Salbutamol, a beta 2-agonist, decreased blood pressure in a dose-dependent manner and induced a biphasic pattern of changes (i.e., an initial decrease with a subsequent increase). The effect of isoproterenol, which is a nonselective beta-agonist, is oriented more to a beta 2-agonist at larger doses. These different effects induced by isoproterenol are probably due to a balance of dominance between beta 1 action and beta 2 action at different doses.
Department of Otorhinolaryngology, Toride Kyodo General Hospital, Ibaraki, Japan.
N
N
Kobayashi
M
M
Hasegawa
K
K
Yokoyama
T
T
Tamura
D000420:Albuterol / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002245:Carbon Dioxide / Q000097:blood; D003051:Cochlea / Q000098:blood supply* / Q000187:drug effects*; D004280:Dobutamine / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D007545:Isoproterenol / Q000008:administration & dosage / Q000494:pharmacology*; D010100:Oxygen / Q000097:blood; D010424:Pentobarbital / Q000494:pharmacology; D012039:Regional Blood Flow / Q000187:drug effects
D002245:Carbon Dioxide; D004280:Dobutamine; D010424:Pentobarbital; D007545:Isoproterenol; D000420:Albuterol; D010100:Oxygen