Table 1.

Age-related inhibitory changes in central auditory systems

StructureFunctionResponseReference
Cochlear nucleusPresynapticLower glycine levels(Banay-Schwartz et al., 1989a; Banay-Schwartz et al., 1989b; Willot et al., 1997)
PostsynapticAltered glycine receptor subunit composition; Loss of strychnine binding(Krenning et al., 1998; Caspary et al., 2001; Milbrandt and Caspary, 1995; Willot et al., 1997)
PhysiologyLoss of on-CF inhibition; Altered temporal responses(Caspary et al., 2005; Caspary et al., 2006)
Inferior colliculusPresynapticReduced GAD level and its activity; Reduced GABA level and its release(McGeer and McGeer, 1975; Caspary et al., 1990; GutiƩrrez et al., 1994; Milbrandt et al., 1994; Raza et al., 1994; Milbrandt et al., 2000)
PostsynapticAltered GABAA receptor subunit composition and quantitative receptor binding(GutiƩrrez et al., 1994; Milbrandt et al., 1996; Milbrandt et al., 1997; Caspary et al., 1999)
PhysiologyLoss of on-CF inhibition, altered SAM responses. Increased spontaneous activity(Palombi and Caspary, 1996a; Palombi and Caspary, 1996b; Palombi and Caspary, 1996c; Shaddock-Palombi et al., 2001; Walton et al., 1997; Walton et al., 1998; Willott et al., 1988)
Auditory cortexPresynapticReduced GAD levels (message and protein)(Ling et al., 2005)
PostsynapticAltered GABAA receptor subunit composition(Ling et al., 2004)
PhysiologyAltered response maps; Reduced reproducibility of response maps; Increased ability to drive complex units with current(Turner et al., 2005a; Turner et al., 2005b; Mendelson and Ricketts, 2001)