-Sodium intake occurs either as a spontaneous or induced behavior, which is enhanced, i.e., sensitized, by repeated episodes of water deprivation followed by subsequent partial rehydration (WD-PR). In the present work, we examined whether repeated WD-PR alters hypothalamic transcripts related to the brain renin-angiotensin system (RAS) and apelin system in male normotensive Holtzman rats (HTZ). We also examined whether the sodium intake of a strain with genetically inherited high expression of the brain RAS, the spontaneously hypertensive rat (SHR), responds differently than HTZ to repeated WD-PR. We found that repeated WD-PR, besides enhancing spontaneous and induced 0.3 M NaCl intake, increased the hypothalamic expression of angiotensinogen, aminopeptidase N, and apelin receptor transcripts (43%, 60%, and 159%, respectively) in HTZ at the end of the third WD-PR. Repeated WD-PR did not change the daily spontaneous 0.3 M NaCl intake and barely changed the need-induced 0.3 M NaCl intake of SHR. The same treatment consistently enhanced spontaneous daily 0.3 M NaCl intake in the normotensive Wistar-Kyoto rats. The results show that repeated WD-PR produces alterations in hypothalamic transcripts and also sensitizes sodium appetite in HTZ. They suggest an association between the components of hypothalamic RAS and the apelin system, with neural and behavioral plasticity produced by repeated episodes of WD-PR in a normotensive strain. The results also indicate that the inherited hyperactive brain RAS is not a guarantee for sensitization of sodium intake in the male adult SHR exposed to repeated WD-PR.angiotensin; apelin; neuroplasticity; rat strain; dehydration; spontaneously hypertensive rat WATER DEPRIVATION, WHICH OCCURS IN everyday life in the wild and in cities, increases the need for sodium replacement in humans and animals, and is a subject of concern for public health (16,20,24,25).In the laboratory, repeated episodes of water deprivation (WD) followed by partial rehydration (PR), or WD-PR protocol, sensitize sodium appetite and spontaneous or daily (needfree) NaCl intake in rats (6). The WD-PR is a useful experimental protocol to separate thirst from sodium appetite in water-deprived rats (5, 6, 38), and possibly in humans (16). The PR period, characterized by full restoration of plasma osmolality, but only partial restoration of the extracellular fluid volume, is attained through ingestion of only water to satiety in a thirst test performed at the end of a cycle of WD. The sodium appetite is then expressed by ingestion of NaCl solution in a sodium appetite test performed immediately after the thirst test, thus restoring sodium balance and extracellular volume (5). The ingestion of NaCl in the sodium appetite test is a behavior that results from the production of transient negative sodium balance because of the obligatory sodium loss in urine during dehydration (5). Because of the sodium loss, the behavior also depends on the production of the neuropeptide ANG II and activation of its receptor type 1, the AT 1...