Evidence that beta 2-receptors mediate action of catecholamines on endolymphatic sac DC potential.
Our recent study has revealed that catecholamines depress the endolymphatic sac direct current potential (ESP) by the beta-adrenergic action [Mori et al., Am. J. Physiol. 259 (regulatory Integrative Comp. Physiol. 28): R921-R924, 1990]. Beta-Adrenergic receptors have been subclassified into beta 1- and beta 2-receptors. Using beta 1-selective (dobutamine) and beta 2-selective (salbutamol) agonists and a beta 1-selective antagonist (atenolol), we determined the subtype of beta-adrenergic receptors that mediate the action of catecholamines on the ESP. Salbutamol depressed the ESP to a larger degree than dobutamine [34.0 +/- 2.6 (n = 7) vs. 13.0 +/- 2.0% (n = 8)] with a much lower dose (100 vs. 1,000 micrograms/kg). Atenolol failed to block the action of salbutamol on the ESP at a dose of 1 mg/kg, whereas propranolol inhibited it at the same dose. The results indicate that beta 2-receptors mediate the action of catecholamines on the ESP.
Mori
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Department of Otolaryngology, Kagawa Medical School, Japan.
Uozumi
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N
D000420:Albuterol / Q000494:pharmacology; D000818:Animals; D002395:Catecholamines / Q000494:pharmacology*; D004280:Dobutamine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D004712:Endolymphatic Sac / Q000502:physiology*; D006168:Guinea Pigs; D007545:Isoproterenol / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000502:physiology*
D002395:Catecholamines; D011943:Receptors, Adrenergic, beta; D004280:Dobutamine; D011433:Propranolol; D007545:Isoproterenol; D000420:Albuterol