Previous studies show that the angiotensin type 1 receptor (AT1R) is susceptible to rapid desensitization, but that more chronic treatments that stimulate angiotensin II (AngII) lead to sensitization of several responses. It is unclear, however, if the processes of desensitization and sensitization interact. To test for differences in AT1R expression associated with single or repeated injections of AngII, we measured AT1R mRNA in nuclei that control fluid intake of rats given AngII either in a single injection or divided into three injections spaced 20 min apart. Rats given a single injection of AngII had more AT1R mRNA in the subfornical organ (SFO) and the periventricular tissue surrounding the anteroventral third ventricle (AV3V) than did controls. The effect was not observed, however, when the same cumulative dose of AngII was divided into multiple injections. Behavioral tests found that single daily injections of AngII sensitized of the dipsogenic response to AngII, but a daily regimen of four injections did not cause sensitization. Analysis of 125I-Sar1-AngII binding revealed a paradoxical decrease in binding in the caudal AV3V and dorsal median preoptic nucleus (dMnPO) after 5 days of single daily injections of AngII; however, this effect was absent in rats treated for 5 days with four daily AngII injections. Taken together, these data suggest that a desensitizing treatment regimen prevents behavior- and receptor-level effects of repeated daily AngII.
- water intake
- drinking microstructure
- fluid balance
- angiotensin II
- Copyright © 2014, American Journal of Physiology - Regulatory, Integrative and Comparative Physiology