[Effects of adenosine on cochlear function in guinea pigs].

As a neuromodulator, adenosine is able to decrease the release of most neurotransmitters and plays a role of negative feedback regulation. In the present experiment, the effects of adenosine, and its uptake inhibitor dipyridamole and antagonist theophylline on cochlear potentials were investigated by means of perilymphatic perfusion. 0.01 mmol/L adenosine and dipyridamole was shown to suppress compound action potentials (CAP) and cochlear microphonics (CM). The amplitudes of CAP and CM were decreased under high sound intensity stimulation. The I/O function curve was shifted toward the right and the N1 peak latency of CAP was prolonged. 1 mmol/L theophylline showed opposite effects. All these changes are reversible after washing out of the artificial perilymphy. Normal endocochlear potentials (EP) and anoxia induced negative EP (N-EP) were not changed significantly, while the rapid response of EP to noise exposure, i.e. a rapid fall with onset of noise (EP-on) and a rapid increase with offset (EP-off), could be suppressed by adenosine. These results suggest that adenosine is an inhibitory neuromodulator subserving a negative feedback role in the regulation of cochlear function.