Abstract
To test the possibility that catecholamines have an influence on the function of the endolymphatic sac (ES), which is known to absorb the endolymph, the effect of catecholamines on the ES direct current potential (ESP) was examined in the guinea pig. The ESP was recorded extradurally by the posterior occipital approach. Isoproterenol (Iso), epinephrine (Epi), and norepinephrine (NE) were administered intravenously for 4 min using an infusion pump. Catecholamines reversibly depressed the ESP with the rank order of potency Iso greater than Epi greater than NE. The threshold doses were 0.021, 0.27, and 1.94 micrograms/kg for Iso, Epi, and NE, respectively. beta-Antagonist (propranolol) blocked the action of catecholamines on the ESP but alpha-antagonist (phentolamine) did not. This indicates that beta-adrenergic action induces the ESP change. This study implies that catecholamines may regulate the function of the ES.
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