Effects of salicylate application on the spontaneous activity in brain slices of the mouse cochlear nucleus, medial geniculate body and primary auditory cortex

Hear Res. 2008 Jun;240(1-2):42-51. doi: 10.1016/j.heares.2008.02.005. Epub 2008 Feb 20.

Abstract

Salicylate is a well-known substance to produce reversible tinnitus in animals and humans as well. It has been shown that systemic application of salicylate changes the neuronal spontaneous activity in several parts of the auditory pathway. The effects observed in central auditory structures in vivo could be based upon the changed afferent cochlear input to the central auditory system or in addition by a direct action of salicylate onto neurons within the auditory pathway. A direct influence of local salicylate application on spontaneous activity of central auditory neurons has already been described for the inferior colliculus (IC) in brain slice preparations. As spontaneous activity within all key structures of the central auditory pathway could play an important role in tinnitus generation, the present study investigated direct effects of salicylate superfusion on the spontaneous activity of the deafferented cochlear nucleus (CN), medial geniculate body (MGB), and auditory cortex (AC) in brain slices. Out of 72 neurons, 73.4% responded statistically significantly to the superfusate by changing their firing rates. 48.4% of them increased and 51.6% decreased their firing rates, respectively. The mean change of firing rate upon salicylate superfusion was 24.4%. All responses were not significantly different between the brain areas. The amount of neurons which responded to salicylate and the mean change of firing rate was much higher in the IC than in the CN, MGB and AC. This contributes to the hypothesis that salicylate-induced tinnitus is a phantom auditory perception mainly related to hyperexcitability of IC neurons. However, the present results suggest that the individual, specific salicylate sensitivity of CN, MGB and AC neurons can modulate the salicylate-induced generation of tinnitus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials
  • Animals
  • Auditory Cortex / drug effects*
  • Auditory Cortex / physiopathology
  • Auditory Pathways / drug effects*
  • Auditory Pathways / physiopathology
  • Cochlear Nucleus / drug effects*
  • Cochlear Nucleus / physiopathology
  • Dose-Response Relationship, Drug
  • Female
  • Geniculate Bodies / drug effects*
  • Geniculate Bodies / physiopathology
  • In Vitro Techniques
  • Male
  • Mice
  • Neurons / drug effects
  • Salicylic Acid / toxicity*
  • Time Factors
  • Tinnitus / chemically induced*
  • Tinnitus / physiopathology

Substances

  • Salicylic Acid