title: Effects of angiotensin II and its blockers Sar1-Ile8-angiotensin II and DuP 753 on drinking in ducks in relation to properties of subfornical organ neurons.
abstract: Properties of systemically applied angiotensin II in stimulating water intake of normally hydrated ducks were studied and the results compared with properties of angiotensin II-responsive neurons of the subfornical organ which are considered as targets for circulating angiotensin II acting as a dipsogen. Following intravenous infusion of hypertonic saline (2000 mosmol.kg-1 at 0.3 ml.min-1 for 1 h), intravenous infusion of 0.3 ml.min-1 isotonic saline with angiotensin II (200 ng.min-1), starting 1 h later, stimulated drinking in each case at an angiotensin II plasma level of about 1400 pg.ml-1. Without hypertonic priming, the same angiotensin II infusion did not stimulate drinking in each experiment; however, if effective, repeated infusions of ANGII induced stable dipsogenic responses. Angiotensin II infusions did not alter plasma levels of antidiuretic hormone. Sar1-Ile8-angiotensin II, a non-selective angiotensin II antagonist, acted weakly as a partial agonist when infused at a dose 200-fold higher than angiotensin II and effectively blocked the dipsogenic action of angiotensin II; this corresponds to the inhibition of angiotensin II-induced excitation by Sar1-Ile8-angiotensin II observed in duck subfornical organ neurons. DuP 753 (losartan), an angiotensin II antagonist specifically blocking AT1 receptors in mammals, had equivocal effects on angiotensin II-induced drinking in ducks at rates 50- and 200-fold higher than angiotensin II, which corresponds to the weak inhibitory action of this compound on angiotensin II-induced neuronal excitation in the duck SFO. Blood pressure was only marginally elevated by the applied angiotensin II dose and Sar1-Ile8-angiotensin II had no effect.
authors.affiliation: Max-Planck-Institute for Physiological and Clinical Research, W.G. Kerckhoff-Institute, Bad Nauheim, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Simon
authors.forename: H A
authors.initials: HA
authors.lastname: Schmid
mesh_terms: D000804:Angiotensin II / Q000031:analogs & derivatives* / Q000097:blood / Q000494:pharmacology* / Q000502:physiology; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D001713:Biphenyl Compounds / Q000494:pharmacology*; D004326:Drinking / Q000187:drug effects* / Q000502:physiology; D004372:Ducks / Q000502:physiology*; D006400:Hematocrit; D007093:Imidazoles / Q000494:pharmacology*; D019808:Losartan; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D009994:Osmolar Concentration; D011945:Receptors, Angiotensin / Q000502:physiology; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage; D013356:Subfornical Organ / Q000187:drug effects* / Q000502:physiology; D013777:Tetrazoles / Q000494:pharmacology*; D014668:Vasotocin / Q000097:blood
chemical_list: D057911:Angiotensin Receptor Antagonists; D001713:Biphenyl Compounds; D007093:Imidazoles; D011945:Receptors, Angiotensin; D012462:Saline Solution, Hypertonic; D013777:Tetrazoles; D000804:Angiotensin II; C009210:sarleucin; D019808:Losartan; D014668:Vasotocin