Morphological change of substance P receptor immunoreactive dendrites of preganglionic sympathetic neurons.
Substance P (SP)-containing terminals and SP receptors (SPRs) are found on the dendrites of preganglionic sympathetic neurons (PSNs) in the intermedio-lateral nucleus (IML) of the spinal cord. The SP-containing fibers were thought to be of supraspinal origin. However, the primary sensory nerve fibers terminated around PSNs, and some of them directly on PSNs. We observed approximately 150 SPR-immunoreactive (ir) varicosities on the dendrites of PSNs in slices of the first thoracic segment (T1) in control rats. The number of varicosities decreased to 41% 14 days after hemisection of the spinal cord at the fourth cervical segment (C4), and to 55% 14 days after sectioning the spinal dorsal roots at the C8 and T1 levels. The number of varicosities decreased by 33% in 8-week-old rats which had been administered capsaicin subcutaneously within 24 hours after birth to eradicate unmyelinated sensory fibers. However, varicosities increased by 15% 15 minutes after injection of capsaicin into the plantar surface of the front paw to stimulate somatosensory nerve fibers in adult rats. The results demonstrate that SPR-ir varicosities on the dendrites of PSNs were modulated not only by the supraspinal nervous system but also directly by the primary sensory nerve terminals.
Ohtori
S
S
Department of Orthopaedic Surgery, School of Medicine, Chiba University, Japan. 97MD0526@insei.m.chiba-u.ac.jp
Chiba
T
T
Takahashi
K
K
Ino
H
H
Moriya
H
H
D000818:Animals; D003712:Dendrites / Q000648:ultrastructure*; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018040:Receptors, Neurokinin-1 / Q000032:analysis*; D013116:Spinal Cord / Q000166:cytology*; D013564:Sympathetic Nervous System / Q000166:cytology*
D018040:Receptors, Neurokinin-1