Korean J Anat.  2000 Apr;33(2):209-218.

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

• Park KP
• Kim KH
• Lee HJ
• Kang JH
• Jang HJ
• Park KD
• Choi BJ
• Bae YC

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.

Keyword

Trigeminal mesencephalic nucleus; Peridontal ligament; GABA; Jaw movement; Ultrastructure

MeSH Terms

Animals
Bite Force
Dendrites
gamma-Aminobutyric Acid
Horseradish Peroxidase
Jaw
Mastication
Neurons
Neurotransmitter Agents
Rats*
Reflex
Horseradish Peroxidase
Neurotransmitter Agents
gamma-Aminobutyric Acid