Effects of angiotensin II and AIII microinjections into the zona incerta after intra- and extracellular fluid loss.
Our recent results showed that angiotensin II or III (AII, AIII) microinjected into the zona incerta (ZI) significantly increased water intake. The most effective doses of AII and AIII were also defined. The two neuropeptides had their effects differently on drinking via different receptors. AII bound to AT(1) that was blocked by AT(1) receptor antagonist Losartan and the effect of AIII was eliminated by prior application of AT(2) receptor antagonist PD 123319. After different hydrational challenges, the effects of AII and AIII in the ZI have never been experimented, however. In the present experiments, the previously defined effective doses of AII (100 ng) or AIII (200 ng) were microinjected into the ZI after different types of challenges: (1). lowered thirst motivation when animals ingested approximately 40% of their daily fluid need during the consequent 60-min-daily-drinking period before the injection, (2). 48-h water deprivation, (3). intracellular dehydration and (4). extracellular dehydration. In all of the cases, incertally injected AII increased the animals' water ingestion. While Losartan could block these effects, PD 123319 was ineffective. Experiments were repeated by AIII, but in none of the cases differences were experienced between the groups. The finding that following hydrational challenges water intake increased only after AII injections and it could be blocked only by Losartan suggests that AII and AT(1) receptor play a pivotal role in the ZI in maintaining the body water balance.
Institute of Physiology and Neurophysiology Research Group of the Hungarian Academy of Sciences and Pécs University Medical School, H-7602 Pécs Pf.: 99., Hungary.
Eva Eszter
EE
Bagi
Eva
E
Fekete
Dániel
D
Bányai
László
L
Lénárd
D000804:Angiotensin II / Q000008:administration & dosage*; D000805:Angiotensin III / Q000008:administration & dosage*; D000818:Animals; D004326:Drinking / Q000187:drug effects / Q000502:physiology; D045604:Extracellular Fluid / Q000187:drug effects* / Q000502:physiology; D007424:Intracellular Fluid / Q000187:drug effects* / Q000502:physiology; D008297:Male; D008845:Microinjections; D051381:Rats; D020530:Subthalamus / Q000187:drug effects* / Q000502:physiology
D000804:Angiotensin II; D000805:Angiotensin III