Synaptic connection and GABA-immunoreactivity of periodontal afferent terminals and their presynaptic endings in the trigeminal motor nucleus of the rat / 대한해부학회지

ABSTRACT

Periodontal-masseteric reflex is implicated in the control of jaw movement and masticatory force during chewing foods. This study is aimed to investigate the synaptic arrangement of mesencephalic periodontal afferents in the trigeminal motor nucleus and to identify the neurotransmitter involved in the presynaptic control of them through the intra-axonal staining of horseradish peroxidase combined with postembedding immunogold methods. Most of the labeled terminals showed synaptic contacts with the small sized dendritic shafts or distal dendrites, while synaptic contacts with the somata or proximal dendrites were not observed. More than one third of the analyzed labeled boutons received presynaptic input from pleomorphic vesicles containing ending (p-ending). About 11% of labeled boutons showed synaptic triads. All the analyzed boutons made synaptic contacts with one to four neuronal profiles and those showing synaptic contact with five or more were not observed. Labeled terminals were larger than presynaptic p-endings. A large number of the analyzed p-endings showed GABA like immunoreactivity. These observations provide evidence that periodontal afferent terminals show very simple and characteristic synaptic arrangements in the trigeminal motor nucleus and that p-endings presynaptic to them may use GABA as a neurotransmitter for presynaptic inhibition.