Differential effects of water deprivation and rehydration on Fos and FosB/ΔFosB staining in the rat brainstem

This study examined the effects of dehydration and rehydration with water on Fos and FosB staining in the brainstem of rats. Male rats were water deprived for 48 h (Dehyd, n = 7) or 46 h followed by 2 h access to water (Rehyd, n = 7). Controls had ad libitum access to water (Con, n = 9). Brainstems were stained for Fos and FosB/ΔFosB using commercially available antibodies. In the nucleus of the solitary tract (NTS), the number of Fos stained neurons was significantly increased by dehydration and increased further following rehydration (Con 5 ± 1; Dehyd 22 ± 1; Rehyd 48 ± 5). The average number of Fos-positive cells in the parabrachial nucleus (PBN) was significantly increased only by rehydration (Con 12 ± 2; Dehyd 6 ± 2; Rehyd 51 ± 4). The area postrema (AP) showed significant increases in Fos staining after dehydration and rehydration (Fos: Con 4 ± 1; Dehyd 28 ± 3; Rehyd 24 ± 3). In the rostral ventrolateral medulla (RVL), Fos staining significantly increased after dehydration and this effect was reduced by rehydration (Con 3 ± 1; Dehyd 21 ± 2; Rehyd 12 ± 1). In contrast, Fos staining in the caudal ventrolateral medulla (CVL) was not significantly influenced following either dehydration or rehydration with water (Con 4 ± 1; Dehyd 4 ± 1; Rehyd 5 ± 1). FosB/ΔFosB staining in the NTS, AP, and RVL was comparably increased by dehydration and rehydration. In the PBN and CVL, FosB/ΔFosB staining was not affected by the treatments. Dehydration and rehydration have regionally specific effects on Fos and FosB/ΔFosB staining in the brainstem.