ALPHA(1)-ADRENERGIC RECEPTORS IN THE MAMMALIAN COCHLEA

The presence of alpha(1)-adrenergic receptors in the mammalian cochlea has previously been suggested by physiological experiments using anta gonists specific to the receptor. However, the characteristcs of adren ergic receptors in the cochlea have not been described. By employing [ H-3]-prazosin, high affinity, specific binding sites with characterist ics of alpha(1)-adrenergic receptors have now been identified and char acterized in the chinchilla cochlea. Analysis of the specific [H-3]-pr azosin binding indicates that prazosin binds to a single class of high -affinity sites with a dissociation constant, k(d), of 2.9 x 10(-9) M and a maximum number of binding sites, B-max, of 30 fmol/mg dry tissue . Furthermore, the binding characteristics suggest that these receptor s may be related to the microvasculature of the cochlea. These results provide a rational basis for the observed actions of alpha-adrenergic drugs on the auditory system.