In this work we used Kiss1-GFP transgenic mice containing the regulatory sequence of the Kiss1 gene linked to a reporter gene (green fluorescent protein, GFP) in the anteroventral periventricular nucleus (AVPV), anterodorsal preoptic nucleus (ADP) and arcuate nucleus (Arc). The objective of this study was to analyze the neuronal ΔFosB activation and cocaine- and the amphetamine-regulated transcript (CART) expression in the AVPV, ADP and in two rostro-to-caudal levels of the Arc in ovariectomized estrogen-primed (OVX+E) Kiss1-GFP mice and control (OVX+OIL) induced by hypertonic salt loading (SL). During 4 days, these groups (n=6, 25 g) had access to burettes containing 0.3M NaCl solution or water. Completed this period, the mice were anesthetized and perfused transcardially. Dual label immunohistochemistry was performed to determine co-expression of GFP immunoreactivity with ΔFosB or CART in the brain structures. Sections were incubated primary antisera against ΔFosB or CART, overnight at room temperature, followed by incubation with secondary antibodies anti-rabbit IgG biotin conjugated (immunoperoxidase) or AlexaFluor-594 (immunofluorescence). The results were expressed as the percentage of neurons with co-localization of ΔFosB-GFP or CART-GFP in relation to the number of Kiss1-GFP neurons. Significance levels were considered at p<0.05. The OVX+OIL group showed an increase in dual label ΔFosB-GFP in the ADP (20%); AVPV (15%); rostral ARC (46%) and caudal Arc (58%) compared to OVX+E group (13%; 6.5%; 32% and 28%, respectively) in response to salt loading. In addition, SL induced an increase in CART-GFP neurons of the rostral ARC (18%) and caudal Arc (27%) in comparison to OVX+E group (6.3%; 12.4%, respectively). Our findings reveal that Kiss1 neurons and CART expression may be involved in a neural network subserving the regulatory response to changes in plasma osmolality. The results also provide strong evidence that estradiol should be the primary modulator of this response to achieve body fluid homeostasis.