THE EFFECT OF ADENOSINE ON COCHLEAR POTENTIALS IN THE GUINEA-PIG

The effect of adenosine on cochlear potentials was examined in the gui nea pig. Perilymphatic perfusion with 10(-4) M adenosine produced a si gnificant decrease in the amplitudes of cochlear microphonics, negativ e summating potential (-SP) and compound action potential (CAP) and si gnificant prolongation of N1 latency with no change in the endocochlea r potential. The decreases in the amplitudes of -SP and CAP caused by adenosine were dose-dependent. Perilymphatic perfusion with an inactiv e analogue, 8-bromoadenosine, produced no changes in the cochlear pote ntials. The A1-receptor agonist, 2-chloroadenosine, produced a similar change in cochlear potentials to adenosine, while no changes were pro duced by the A2-receptor agonist ,5'-(N-ethylcarboxamido)-adenosine. T hese results suggest that adenosine may have a medulatory function thr ough an A1 receptor in the cochlea.