抄録
Excitatory synaptic transmission from the reticular formation around the trigeminal motor nucleus (MoV) to trigeminal motoneurons (TMNs) in rat brain stem slice preparations was studied by high-speed optical recording techniques and gramicidin perforated-patch recordings. Slices were stained with the voltage-sensitive dye Di-4-ANEPPS and optical signals were analyzed by a CCD camera system (MiCAM01, Brain Vision). Electrical stimulation of the reticular formation located dorsal to MoV (dRF), evoked excitatory responses in MoV. Stimulation of MoV antidromically evoked an excitatory response in dRF under suppression of synaptic transmission by substitution of external Ca2+ with Mn2+. Application of CNQX (20 μM) and APV (20 μM) reduced the excitatory response in MoV evoked by dRF stimulation in both neonatal and juvenile rats. Application of strychnine (5 μM) to MoV also suppressed the excitatory response in MoV of neonatal rats. Gramicidin perforated-patch recordings from TMNs revealed that glycinergic postsynaptic potentials in TMNs evoked by dRF stimulation were depolarizing. In contrast to neonatal animals, application of strychnine to MoV in juveniles enhanced the excitatory response in MoV. We conclude that interneurons in dRF excite TMNs through activation of glutamate or glycine receptors in neonatal rats, whereas glycine receptor activation in TMNs becomes inhibitory in juveniles. Such developmental change of synaptic transmission from dRF to MoV might be involved in the transition from suckling to mastication. [Jpn J Physiol 54 Suppl:S155 (2004)]
