title: Actions of norepinephrine and angiotensin II on aortic rings of adult and aged normotensive and hypertensive rats.
abstract: Development of desensitization to physiologic concentration of norepinephrine (NE 10(-9) M) and its effects on angiotensin II (AII) tachyphylaxis in the aortic rings of adult and aged normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were investigated. Aortic rings of all animals developed desensitization to 10(-9) M NE and tachyphylaxis to AII (10(-9)-10(-6) M). In normotensive WKY, the response to NE and AII was not affected by age, whereas in SHR desensitization to NE and tachyphylaxis to AII were significantly more marked in aged animals. The desensitization to 10(-9) M NE appeared to be homologous because this physiologic concentration of NA significantly attenuated tachyphylaxis to AII (for concentrations of 10(-8)-10(-6) M) in the aortic rings of both adult and aged WKY. Tachyphylaxis to AII was not affected by 10(-9) M NE in either adult or aged SHR, however. These data support our previous finding of similar attenuation of AII tachyphylaxis by NE in aortic rings of normotensive Sprague-Dawley rats, and indicate that absence of such attenuation in SHR; the latter finding could reflect a probable lesion in the interactive pathways of these two vasoconstrictors in hypertensive rats.
authors.affiliation: Department of Pharmacology, Faculty of Medicine, National University of Singapore.
authors.forename: S C
authors.initials: SC
authors.lastname: Kuttan
authors.forename: M K
authors.initials: MK
authors.lastname: Sim
mesh_terms: D000375:Aging / Q000502:physiology*; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000187:drug effects* / Q000503:physiopathology; D006973:Hypertension / Q000503:physiopathology*; D066298:In Vitro Techniques; D009638:Norepinephrine / Q000494:pharmacology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013618:Tachyphylaxis / Q000502:physiology; D014661:Vasoconstriction / Q000187:drug effects
chemical_list: D000804:Angiotensin II; D009638:Norepinephrine