In the rat cortical collecting duct (CCD), epinephrine inhibits vasopressin (AVP)-dependent water permeability and Na⁺ reabsorption. Although inhibition is reversed by the ₂-adrenoceptor (AR) antagonist yohimbine, suggesting the epinephrine effect is primarily mediated by an ₂-AR [C. T. Hawk, L. H. Kudo, A. J. Rouch, and J. A. Schafer. Am. J. Physiol. 265 (Renal Fluid Electrolyte Physiol. 34): F449-F460, 1993], there are also suggestions of an effect at an additional receptor, perhaps an ₁-AR. For the present experiments, we used RT-PCR of total RNA extracted from 1 to 5 mm of microdissected CCDs from rat kidney to identify the -AR isoforms expressed. Specific primers for the ₂-ARs amplifying from the 6th transmembrane (TM) to the 3'-untranslated regions, revealed the presence of _2A and _2B. Western blot analysis also indicated the presence of _2B-AR at the protein level. Degenerate ₁-AR primers that amplify from conserved regions of TM-1 to TM-5, as well as specific primers that amplify either the same region (_1B), the carboxy terminus (_1A), or within the third cytoplasmic loop (_1D), indicated the presence of all three ₁-ARs. Measurement of transepithelial voltage in isolated perfused renal tubules indicated a small inhibitory effect mediated by ₁-ARs. Although the functional effects of epinephrine on AVP-dependent transport processes appear to be mediated predominantly by an ₂-AR, a small contribution to the overall -AR effect may be due to simultaneous activation of an ₁-AR.