抄録
The lateral superior olive (LSO) is the first auditory center that processes differences in the sound level between the two ears. Here we report the developmental changes in GABAB receptor-mediated presynaptic inhibition of GABAergic and/or glycinergic synaptic transmission onto developing rat LSO neurons. MNTB-evoked GABAergic and/or glycinergic inhibitory postsynaptic currents (IPSCs) were recorded from LSO neurons of acute brain stem slices at postnatal (P) 2 to 20 day old rats divided in three groups (P2–6, P8–12, P16–20) using conventional whole-cell patch clamp technique. The pharmacological isolation of MNTB-evoked inhibitory transmission revealed a developmental switch from GABAergic to glycinergic IPSCs during these developmental stages. Bath application of baclofen, a selective GABAB receptor agonist, greatly reduced IPSC amplitude in neonatal (< P6) with a significant change in the paired-pulse ratio, and these effects were eliminated in the presence of GABAB receptor antagonist, suggesting that baclofen acts presynaptic GABAB receptors to reduce the release probability of GABA and/or glycine from presynaptic nerve terminals. However, the GABAB receptor-mediated presynaptic inhibition was gradually reduced with postnatal development so that baclofen had little effect on MNTB-evoked IPSCs recorded from P16–20 LSO neurons. Based on these results, the functional roles of presynaptic GABAB receptors in the development of LSO neurons will be further investigated and discussed. [Jpn J Physiol 55 Suppl:S132 (2005)]
