Orexins in rat dorsal motor nucleus of the vagus potently stimulate gastric motor function.
Orexins regulate food intake, arousal, and the sleep-wake cycle. They are synthesized by neurons in the lateral hypothalamus and project to autonomic areas in the hindbrain. Orexin A applied to the dorsal surface of the medulla stimulates gastric acid secretion via a vagally mediated pathway. We tested the hypothesis that orexins in the dorsal motor nucleus (DMN) of the vagus regulate gastric motor function. Multibarelled micropipette assemblies were used to administer vehicle, L-glutamate, orexins A (1 and 10 pmol) and B (10 pmol), and a dye marker into this site in anesthetized rats. When the pipette was positioned in the DMN rostral to the obex (where excitation of neurons by L-glutamate evoked an increase in contractility), orexins A and B increased intragastric pressure and antral motility. In contrast, 10 pmol orexin A microinjected into the DMN caudal to the obex (where L-glutamate evokes gastric relaxation through a vagal inhibitory pathway) did not significantly alter gastric motor function. In separate immunocytochemical studies, orexin receptor 1 was highly expressed in neurons in the DMN. Specifically, it was present in retrogradely labeled preganglionic neurons in the DMN that innervate the stomach. These data are consistent with the idea that orexin A stimulates vagal excitatory motor neurons. These are the first data to suggest that orexins in the DMN have potent and long-lasting effects to increase gastric contractility.
Department of Pharmacology and Center of Excellence for Neuroscience, Louisiana State University Health Sciences Center, New Orleans 70112, USA.
Zbigniew K
ZK
Krowicki
Melissa A
MA
Burmeister
Hans-Rudolf
HR
Berthoud
Roisin T
RT
Scullion
Kristine
K
Fuchs
Pamela J
PJ
Hornby
D000818:Animals; D002352:Carrier Proteins / Q000008:administration & dosage / Q000494:pharmacology / Q000502:physiology*; D005769:Gastrointestinal Motility / Q000187:drug effects / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000502:physiology*; D008845:Microinjections; D009479:Neuropeptides / Q000008:administration & dosage / Q000494:pharmacology / Q000502:physiology*; D000068797:Orexins; D011312:Pressure; D011706:Pyloric Antrum / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013270:Stomach / Q000187:drug effects / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology*
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins