Hypocretin-1 causes G protein activation and increases ACh release in rat pons.
The effects of the arousal-promoting peptide hypocretin on brain stem G protein activation and ACh release were examined using 16 adult Sprague-Dawley rats. In vitro[35S]GTPgammaS autoradiography was used to test the hypothesis that hypocretin-1-stimulated G protein activation is concentration-dependent and blocked by the hypocretin receptor antagonist SB-334867. Activated G proteins were quantified in dorsal raphe nucleus (DR), locus coeruleus (LC) and pontine reticular nucleus oral part (PnO) and caudal part (PnC). Concentration-response data revealed a significant (P < 0.001) effect of hypocretin-1 (2-2000 nm) in all brain regions examined. Maximal increases over control levels of [35S]GTPgammaS binding were 37% (DR), 58% (LC), 52% (PnO) and 44% (PnC). SB-334867 (2 micro m) significantly (P < 0.002) blocked hypocretin-1 (200 nm)-stimulated [35S]GTPgammaS binding in all four nuclei. This is the first autoradiographic demonstration that hypocretin-1 activates G proteins in arousal-related brain stem nuclei as a result of specific receptor interactions. This finding suggests that some hypocretin receptors in brain stem couple to inhibitory G proteins. In vivo microdialysis was used to test the hypothesis that PnO administration of hypocretin-1 increases ACh release in PnO. Dialysis delivery of hypocretin-1 (100 micro m) significantly (P < 0.002) increased (87%) ACh release. This finding is consistent with the interpretation that one mechanism by which hypocretin promotes arousal is by enhancing cholinergic neurotransmission in the pontine reticular formation.
Bernard
René
R
Departments of Pharmacology and Anaesthesiology, University of Michigan, 7433 Medical Sciences Building I, 1150 West Medical Center Drive, Ann Arbor, MI 48109, USA.
Lydic
Ralph
R
Baghdoyan
Helen A
HA
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D001345:Autoradiography; D001583:Benzoxazoles / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism* / Q000494:pharmacology; D003956:Dialysis; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000493:pharmacokinetics; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D009287:Naphthyridines; D009479:Neuropeptides / Q000378:metabolism* / Q000494:pharmacology; D064446:Orexin Receptors; D000068797:Orexins; D011149:Pons / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide / Q000037:antagonists & inhibitors; D013460:Sulfur Isotopes / Q000493:pharmacokinetics; D013997:Time Factors; D014508:Urea / Q000031:analogs & derivatives* / Q000494:pharmacology
C420062:1-(2-methylbenzoxazol-6-yl)-3-(1,5)naphthyridin-4-yl urea; D001583:Benzoxazoles; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009287:Naphthyridines; D009479:Neuropeptides; D064446:Orexin Receptors; D000068797:Orexins; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide; D013460:Sulfur Isotopes; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D014508:Urea; D019204:GTP-Binding Proteins; D000109:Acetylcholine