Atypical angiotensin receptors may mediate water intake induced by central injections of angiotensin II and of serotonin in pigeons.
Intracerebroventricular (i.c.v.) injection of serotonin (5-HT) in pigeons dose-dependently evokes a prompt and intense drinking behavior, which resembles that evoked by i.c.v. injections of angiotensin II (ANGII) in the same species. In the present study, we have examined the possible participation of central ANGII receptors in both ANGII- and 5-HT-evoked drinking behavior. The effects of i.c.v. injections of 5-HT (155 nmol), avian ANGII ([Asp(1),Val(5)]-ANGII, 0.1 nmol) or vehicle were studied in pigeons pretreated 20 min before with i.c.v. injections of the nonspecific ANGII receptor antagonist [Sar(1),Ile(8)]-ANGII (SAR; 1, 0.1 or 0.01 nmol), the AT(1) receptor antagonist losartan (2 or 4 nmol), the AT(2) receptor antagonist PD 123,319 (2 or 4 nmol) or vehicle (NaCl 0.15 M, 1 microl, n = 8/group). Immediately after treatment, they were given free access to water and drinking behavior was recorded during the next 60 min. At the doses presently used both 5-HT and ANGII treatments evoked comparable water intake amounts with similar behavioral profiles. While pretreatment with SAR dose-dependently reduced the water intake evoked by both 5-HT and ANGII, neither losartan nor PD 123,319 pretreatment affected the drinking induced by these treatments. The present results indicate that ANGII- and 5-HT-induced drinking in pigeons may be mediated by AT receptors possibly different from mammalian AT(1) and AT(2) receptors and suggest that activation of ANGII central circuits is a necessary step for the intense drinking induced by i.c.v. injections of 5-HT in this species.
Department of Physiological Sciences - CCB, Federal University of Santa Catarina, 88049-900 SC, Florianópolis, Brazil.
S R
SR
Brun
V
V
da Luz
M
M
Fernandez
M A
MA
Paschoalini
J
J
Marino-Neto
D015059:1-Sarcosine-8-Isoleucine Angiotensin II / Q000008:administration & dosage / Q000494:pharmacology; D000804:Angiotensin II / Q000008:administration & dosage / Q000819:agonists / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D010856:Columbidae / Q000502:physiology*; D004327:Drinking Behavior / Q000187:drug effects*; D007093:Imidazoles / Q000494:pharmacology; D007276:Injections, Intraventricular; D019808:Losartan / Q000494:pharmacology; D008297:Male; D011725:Pyridines / Q000494:pharmacology; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000819:agonists / Q000378:metabolism*; D012701:Serotonin / Q000008:administration & dosage / Q000494:pharmacology*
D057911:Angiotensin Receptor Antagonists; D007093:Imidazoles; D011725:Pyridines; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D000804:Angiotensin II; C073402:PD 123319; D012701:Serotonin; D015059:1-Sarcosine-8-Isoleucine Angiotensin II; D019808:Losartan