title: Effects of central hypocretin-1 administration on hemodynamic responses in young-adult and middle-aged rats.
abstract: The prevalence of hypertension in middle age correlates with impaired autonomic regulation and as norepinephrinergic neurons decline with increasing age, and this reduction may contribute to this impairment. Central hypocretin-activated norepinephrinergic neurons contribute to sympathetic regulation. In the present study we compared sympathoadrenal effects of intracerebroventricular (i.c.v.) hypocretin-1(5 nmol) between young-adult (12-14 weeks) and middle-aged (12-14 months) rats. Arterial blood pressure, heart rate and plasma catecholamines were assessed under pentobarbital anesthesia. In addition, we compared hypocretin-1 and K(+)-evoked norepinephrine release from the cerebrocortical slices prepared from young-adult and middle-aged rats. We also examined whether the novel hypocretin receptor-1 antagonist (SB-334867) could reverse these hypocretin-1 effects both in vivo and in vitro. I.c.v. hypocretin-1 significantly increased blood pressure by some 7%, heart rate by 9% and plasma norepinephrine concentrations by 100% in young-adult rats. In middle-aged rats these parameters did not change. Plasma epinephrine did not increase in either group. There was a significant correlation between changes in mean arterial pressure and plasma norepinephrine. Similarly, hypocretin-1 evoked norepinephrine release from cerebrocortical slices prepared from young-adult rats was significantly higher than that of middle-aged rats whilst K(+)-evoked release did not differ between the groups. SB-334867 significantly attenuated hypocretin-1-increased blood pressure and both in vivo and in vitro norepinephrine release. The present data suggest that hypocretinergic neurons may contribute to the regulation of central but not adrenal sympathetic activity. Moreover, sympathetic regulation by hypocretinergic neurones may disappear in middle-age in rats.
authors.affiliation: Department of Anesthesiology, University of Hirosaki School of Medicine, 036-8563 Hirosaki, Japan.
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Hirota
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Kushikata
authors.forename: Mihoko
authors.initials: M
authors.lastname: Kudo
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Kudo
authors.forename: Darren
authors.initials: D
authors.lastname: Smart
authors.forename: Akitomo
authors.initials: A
authors.lastname: Matsuki
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D001583:Benzoxazoles / Q000494:pharmacology; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000187:drug effects; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004195:Disease Models, Animal; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology*; D006454:Hemoglobins / Q000378:metabolism; D066298:In Vitro Techniques; D007276:Injections, Intraventricular / Q000379:methods; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D009287:Naphthyridines; D009479:Neuropeptides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009638:Norepinephrine / Q000097:blood; D000068797:Orexins; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D013997:Time Factors; D014508:Urea / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: C420062:1-(2-methylbenzoxazol-6-yl)-3-(1,5)naphthyridin-4-yl urea; D001583:Benzoxazoles; D002352:Carrier Proteins; D006454:Hemoglobins; D047908:Intracellular Signaling Peptides and Proteins; D009287:Naphthyridines; D009479:Neuropeptides; D000068797:Orexins; D011189:Potassium Chloride; D014508:Urea; D009638:Norepinephrine