The effects of quinine on cochlear nerve fibre activity in the guinea pig.
The effect of quinine on single cochlear nerve fibre activity (n = 38) was measured in four pigmented guinea pigs, which were given 10-30 mg/kg of quinine intravenously. The frequency tuning curves of these fibres exhibited significant increases in the thresholds of both 'tip' and 'tails' regions of the frequency tuning curve, but these changes did not appear to be accompanied by significant changes in tuning, as measured by the Q'10'dB. In comparison with control fibres (n = 178) from 13 untreated animals, significant changes in the proportion of low:high spontaneous rates (SR) were also seen. Using a boundary criterion of 25 sp/s, this rate changed from 26:74% to 47:53% in control and quinine-poisoned fibres, respectively. Independent of changes in the spontaneous rate, significant increases in the mean absolute refractory period from 0.85 to 1 ms were measured following quinine administration. The absence of a significant effect on fibre tuning whilst threshold was elevated indicates that quinine does not affect the integrity of the cochlear amplifier, though appears to affect cochlear sensitivity.
Mulheran
M
M
The MRC Toxicology Unit, Centre for Mechanisms Human Toxicity, University of Leicester, UK.
D000161:Acoustic Stimulation; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D003056:Cochlear Nerve / Q000187:drug effects* / Q000502:physiology; D004056:Differential Threshold / Q000187:drug effects; D006168:Guinea Pigs; D009412:Nerve Fibers / Q000187:drug effects* / Q000502:physiology; D011803:Quinine / Q000494:pharmacology*; D012032:Refractory Period, Electrophysiological / Q000187:drug effects; D013997:Time Factors
D011803:Quinine