Local axonal arborization patterns of distinct neuronal types in the caudal nucleus of the tractus solitarius.
Neurons in the caudal nucleus of the tractus solitarius (cNTS) are quite heterogeneous in cell size (50 to 450 microm(2) in somal area) and other morphologic characteristics. For a more objective classification of cNTS neurons, their morphologic features were analyzed quantitatively based on reconstructed biocytin-filled cells after whole-cell patch-clamp recordings. According to the patterns of axonal branching behaviors, cNTS cells could be classified into two groups: smaller cells (94.1 microm(2) in mean somal area, range 62-120 microm(2), n = 22) and larger cells (245 microm(2) in mean somal area, range 142-411 microm(2), n = 23). Extensive axonal arborization with numerous possible synaptic boutons was specifically associated with smaller neurons, while larger cells possessed no or few axon collaterals, suggesting their distinct roles as local circuit neurons (or interneurons) and projection neurons, respectively. With regard to somatodendritic characteristics, the following correlations with cell size were found: smaller cells had larger form factors than larger cells (P < 0.05). Larger neurons had more extensive dendritic arborization, expressed by total dendritic length (P < 0.01) and number of dendritic branching points (P < 0.01), than smaller cells. It was suggested that small cNTS neurons contribute specifically to an integration of input information generated in the local circuits, while large neurons convey the integrated information to other autonomic brain regions.
Department of Anatomy I, Jikei University School of Medicine, 3-25-8 Nishi-Shimbashi Minato-ku, Tokyo 105-8461, Japan.
Tomoaki
T
Okada
Masayuki
M
Yoshioka
Kiyoharu
K
Inoue
Yoshinori
Y
Kawai
D000818:Animals; D001369:Axons / Q000145:classification / Q000502:physiology / Q000648:ultrastructure*; D048429:Cell Size; D003712:Dendrites / Q000502:physiology / Q000648:ultrastructure; D007395:Interneurons / Q000502:physiology / Q000648:ultrastructure; D008239:Lysine / Q000031:analogs & derivatives; D008297:Male; D009434:Neural Pathways / Q000166:cytology* / Q000502:physiology; D009474:Neurons / Q000145:classification / Q000166:cytology* / Q000502:physiology; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D017729:Presynaptic Terminals / Q000502:physiology / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D017552:Solitary Nucleus / Q000166:cytology* / Q000502:physiology; D017833:Visceral Afferents / Q000166:cytology / Q000502:physiology
C013411:biocytin; D008239:Lysine