Quantitative Ultrastructural Analysis of Endings Presynaptic to the Tooth Pulp Afferent Terminals in the Trigeminal Oral Nucleus.
10.11620/IJOB.2016.41.3.133
- Author:
Suk Ki LEE
1
;
Tae Heon KIM
;
Cheon Hee LEE
;
Sook Kyung PARK
;
Yong Chul BAE
Author Information
1. Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu 700-412, Korea. ycbae@knu.ac.kr
- Publication Type:Original Article
- Keywords:
tooth pulp;
afferent;
presynatptic ending;
ultrastructure;
morphometry
- MeSH:
Animals;
Horseradish Peroxidase;
Incisor;
Mitochondrial Size;
Rats;
Tooth*;
Trigeminal Nuclei
- From:International Journal of Oral Biology
2016;41(3):133-139
- CountryRepublic of Korea
- Language:Korean
-
Abstract:
The ultrastructural parameters related to synaptic release of endings which are presynaptic to tooth pulp afferent terminals (p-endings) were analyzed to understand the underlying mechanism for presynaptic modulation of tooth pulp afferents. Tooth pulp afferents were labelled by applying wheat-germ agglutinin conjugated horseradish peroxidase to the rat right lower incisor, whereafter electron microscopic morphometric analysis with serial section and reconstruction of p-endings in the trigeminal oral nucleus was performed. The results obtained from 15 p-endings presynaptic to 11 labeled tooth pulp afferent terminals were as follows. P-endings contained pleomorphic vesicles and made symmetrical synaptic contacts with labeled terminals. The p-endings showed small synaptic release-related ultrastructural parameters: volume, 0.82 ± 0.45 µm³ (mean ± SD); surface area, 4.50 ± 1.76 µm²; mitochondrial volume, 0.15 ± 0.07 µm³; total apposed surface area, 0.69 ± 0.24 µm²; active zone area, 0.10 ± 0.04 µm²; total vesicle number, 1045 ± 668.86; and vesicle density, 1677 ± 684/µm². The volume of the p-endings showed strong positive correlation with the following parameters: surface area (r=0.97, P<0.01), mitochondrial volume (r=0.56, P<0.05), and total vesicle number (r=0.73, P<0.05). However, the volume of p-endings did not positively correlate or was very weakly correlated with the apposed surface area (r=-0.12, P=0.675) and active zone area (r=0.46, P=0.084). These results show that some synaptic release-related ultrastructural parameters of p-endings on the tooth pulp afferent terminals follow the "size principle" of Pierce and Mendell (1993) in the trigeminal nucleus oralis, but other parameters do not. Our findings may demonstrate a characteristic feature of synaptic release associated with p-endings.
