Synaptic organization of tooth pulp afferent terminals in the rat trigeminal sensory nuclei.
Previous studies provide evidence that a structure/function correlation exists in the distinct zones of the trigeminal sensory nuclei. To evaluate this relationship, we examined the ultrastructure of afferent terminals from the tooth pulp in the rat trigeminal sensory nuclei: the principalis (Vp), the dorsomedial part of oral nucleus (Vdm), and the superficial layers of caudalis (Vc), by using transganglionic transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). A total of 93 labeled boutons were serially sectioned, in which some sections were incubated with gamma-aminobutyric acid (GABA) antiserum. Almost all labeled boutons formed asymmetric contact with nonprimary dendrites, in which more than half of labeled boutons in the Vc made synapses with their spines. The labeled boutons could be divided into two types on the basis of numbers of dense-cored vesicles (DCVs) in a boutons: S-type and DCV-type. Almost all labeled boutons in the Vp and Vdm were S-type, whereas two types were distributed evenly in the Vc. In contrast to DCV-type boutons, the S-type was frequently postsynaptic to unlabeled axon terminals containing a mixture of round, oval, and flattened vesicles (p-endings) and forming symmetrical synapses. Most p-endings examined were immunoreactive to GABA. The frequency of axoaxonic contacts was higher for labeled boutons in the Vp than in the Vdm and Vc. These results suggest that the three structures of trigeminal sensory nuclei serve distinct functions in nociceptive processing.
Bae
Yong Chul
YC
Department of Oral Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, 700-422, Korea. ycbae@knu.ac.kr
Kim
Jong Pil
JP
Choi
Byung Ju
BJ
Park
Kuk Pil
KP
Choi
Min Ki
MK
Moritani
Masayuki
M
Yoshida
Atsushi
A
Shigenaga
Yoshio
Y
D000344:Afferent Pathways / Q000166:cytology*; D000818:Animals; D003782:Dental Pulp / Q000294:innervation*; D008297:Male; D008854:Microscopy, Electron; D017729:Presynaptic Terminals / Q000648:ultrastructure*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000648:ultrastructure; D014070:Tooth / Q000294:innervation; D014278:Trigeminal Nuclei / Q000737:chemistry / Q000166:cytology*; D005680:gamma-Aminobutyric Acid / Q000032:analysis
D005680:gamma-Aminobutyric Acid