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ow nloaded from 2Abstract: Effects of aromatic solvents on acoustic reflexes mediated by central auditory pathways. From previous in vivo investigations, it has been shown that toluene can mimic the effects of cholinergic receptor antagonists and may thereby modify the response of protective acoustic reflexes. The current study aimed to define the relative effects of aromatic solvents on the middle-ear and inner-ear acoustic reflexes. Toward this end, the cochlear microphonic (CMP) elicited with a band noise centered at 4-kHz and the compound action potential (CAP) elicited with 4-kHz tone pips were measured in rats. Both potentials were recorded before, during and after triggering the protective reflexes by a 110-dB SPL contralateral octave band noise centered at 12.5 kHz (12.5 kHz-OBN). In several rats, the middle-ear muscles were severed to identify the relative effects of toluene on the two reflexes. While the reflex elicitor was capable of decreasing both the CMP and CAP amplitudes, an injection of 116.2-mM toluene canceled this suppressor effect induced by the contralateral sound. In the rats wit