THE USE OF THE CA-EXPERIMENTS WITH NOISE EXPOSURE(+ ANTAGONISTIC DRUGDIL TIAZEM IN ANIMAL)

Hearing thresholds at 1-2-4-6 and 8 kHz were determined by brainstem e voced response audiometry (BERA) in 24 guinea pigs. The animals were t hen divided into 6 groups. Group 1 (controls) received no drugs and we re not exposed to noise. Group 2 were given 15 mg/24 h/kg diltiazem s. c. for 13 days. Group 4 was exposed to the same noise as group 3 but w as also treated with diltiazem 15 mg/kg/24 h from three days before no ise exposure until the end of the experiment. Group 5 was exposed to a 110 dB SPL broad-band noise for 3 h daily for 10 days. Group 6 was ex posed to the same noise as group 5 and was treated with diltiazem 15 m g/kg/24 h from three days before noise exposure until the end of the e xperiment. After the last noise exposure hearing thresholds were deter mined again by BERA and were found to be unchanged in those animals tr eated with the drug alone and the controls. In those groups with drug administration and noise exposure hearing loss was less than in the an imals exposed to noise alone. This difference was more pronounced in t he 90 dB groups than in the 110 dB groups.