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.
Cardiovascular Neuroscience Group, Cardiovascular Medicine and Centre for Neuroscience, Flinders University, Bedford Park, SA 5042, Australia. ida.llewellyn-smith@flinders.edu.au
I J
IJ
Llewellyn-Smith
C L
CL
Martin
J N
JN
Marcus
M
M
Yanagisawa
J B
JB
Minson
T E
TE
Scammell
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