Orexin-immunoreactive inputs to rat sympathetic preganglionic neurons.
Orexin increases blood pressure and orexin-immunoreactive (IR) axons robustly innervate the spinal cord. Seeking anatomical evidence for direct effects of orexin on sympathetic preganglionic neurons (SPN), we used immunohistochemistry to study the relationships between orexin-IR axons and SPN identified by immunoreactivity for choline acetyltransferase (ChAT) or for cholera toxin B retrogradely transported from the superior cervical ganglion (SCG). In the intermediolateral cell column (IML), varicose, orexin-positive axons closely apposed almost all SPN in segments T1 and T2, but appositions were rare in T4-L2. Orexin fibers also apposed ChAT-IR cell bodies in the intercalated nucleus and the central autonomic area from T1 to L2. Orexin-IR synapses were identified ultrastructurally on SPN projecting to the SCG. Since SPN involved in cardiovascular control cluster in the IML of mid- and lower thoracic cord, these findings suggest that orexin affects blood pressure by acting on supraspinal neurons rather than SPN.
Llewellyn-Smith
I J
IJ
Cardiovascular Neuroscience Group, Cardiovascular Medicine and Centre for Neuroscience, Flinders University, Bedford Park, SA 5042, Australia. ida.llewellyn-smith@flinders.edu.au
Martin
C L
CL
Marcus
J N
JN
Yanagisawa
M
M
Minson
J B
JB
Scammell
T E
TE
D000109:Acetylcholine / Q000378:metabolism; D000320:Adrenergic Fibers / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D001339:Autonomic Fibers, Preganglionic / Q000378:metabolism* / Q000648:ultrastructure; D017704:Baroreflex / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism*; D002772:Cholera Toxin / Q000378:metabolism / Q000493:pharmacokinetics; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D004525:Efferent Pathways / Q000378:metabolism* / Q000648:ultrastructure; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008854:Microscopy, Electron; D009479:Neuropeptides / Q000378:metabolism*; D000068797:Orexins; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000378:metabolism* / Q000648:ultrastructure; D017783:Superior Cervical Ganglion / Q000378:metabolism
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins; D002772:Cholera Toxin; D002795:Choline O-Acetyltransferase; D000109:Acetylcholine