Ultrastructure of ascending cholinergic terminals in the anteroventral thalamic nucleus of the rat: a comparison with the mammillothalamic terminals.
In this study, to identify the ultrastructure and distribution of ascending cholinergic afferent terminals in the anteroventral thalamic nucleus, we used an anti-vesicular acetylcholine transporter antibody as marker of cholinergic afferents, and characterized the immunoreactive terminals at the ultrastructural level. We then compared the distribution pattern of the cholinergic terminals and that of the mammillothalamic terminals identified by anterograde transport of a tracer injected into the mammillary body. The cholinergic terminals were small, and formed both symmetrical and asymmetrical synaptic contacts throughout the dendritic arborizations, particularly in the distal region. This distribution pattern differed from that of mammillothalamic terminals, that were of LR (large terminal containing round synaptic vesicles) type and were preferentially distributed in the proximal region of dendrites. We also found relatively numerous cholinergic terminals making contact directly with immunonegative excitatory terminals, both LR and SR (small terminal containing round vesicles) terminals, without clear postsynaptic specialization. A few cholinergic terminals even seemed to form a synaptic complex with the LR or SR terminals. These findings suggest that the ascending cholinergic afferents in the anteroventral thalamic nucleus can effectively modulate excitatory inputs from both the mammillothalamic and corticothalamic terminals, in close vicinity to a synaptic site.
Oda
Satoko
S
Department of Anatomy, Toho University School of Medicine, Tokyo, Japan. odas@med.toho-u.ac.jp
Kuroda
Masaru
M
Kakuta
Sachiko
S
Tanihata
Sachiko
S
Ishikawa
Youichi
Y
Kishi
Kiyoshi
K
D000818:Animals; D020643:Anterior Thalamic Nuclei / Q000166:cytology*; D002352:Carrier Proteins / Q000032:analysis; D002799:Cholinergic Fibers / Q000737:chemistry / Q000648:ultrastructure*; D003712:Dendrites / Q000737:chemistry / Q000648:ultrastructure; D007150:Immunohistochemistry; D008297:Male; D008326:Mammillary Bodies / Q000166:cytology*; D026901:Membrane Transport Proteins; D008854:Microscopy, Electron; D017729:Presynaptic Terminals / Q000737:chemistry / Q000648:ultrastructure*; D051381:Rats; D017207:Rats, Sprague-Dawley; D050494:Vesicular Acetylcholine Transport Proteins; D033921:Vesicular Transport Proteins
D002352:Carrier Proteins; D026901:Membrane Transport Proteins; C493461:Slc18a3 protein, rat; D050494:Vesicular Acetylcholine Transport Proteins; D033921:Vesicular Transport Proteins