COMBINED EFFECTS OF ACUTE LEAD ACETATE EXPOSURE AND TONE EXPOSURE OF THE GUINEA-PIG COCHLEA

Lead acetate exposure to humans can induce various disorders of the cr anial nerves. Although vertigo and sensorineural deafness have been re ported in lead workers, the dose effects of lead acetate on the cochle a and eighth cranial nerve are not well documented. We investigated th e effects of lead acetate on the male albino Hartley guinea pig cochle a by measuring cochlear microphonics (CM), whole nerve action potentia l (AP), endocochlear potential (EP) and K+ ion concentration of the en dolymph. Animals were given lead acetate by intraperitoneal injection as 20 mg/week for 4 consecutive weeks. A total dose < 80 mg did not in duce electrophysiological changes in the cochlea. However, the AP outp ut voltage (N-1) decreased if the 80 mg lead acetate treatment was fol lowed by an 80 dB tone exposure at 6 kHz during 24 h. A change was obs erved in CM and EP but not KC ion concentration in the scala media.