Changes in hypothalamic 5-HT_2CR pre-RNA editing in aged male or female mice exposed to novelty stress.

<p>(A) Male mice, (B) Female mice. The hypothalami were harvested 6 h after stress exposure in 18 h-fasted mice. Data are presented as the mean ± SEM (young and aged stressed group; n = 8, aged male control group; n = 5, aged female control group; n = 7). *, p < 0.05 vs. young control group.</p

Changes in plasma ghrelin levels and preproghrelin mRNA expression in aged female mice exposed to novelty stress.

<p>Changes in the plasma levels of acylated ghrelin (A), desacylated ghrelin (B), gastric (left panel) and hypothalamic (right panel) preproghrelin mRNA expression (C) in the free-fed condition and the effects of a 5-HT_2CR antagonist and endogenous ghrelin enhancer on plasma ghrelin levels in aged female mice exposed to novelty stress or not after an 18 h fast (D). The 5-HT_2CR antagonist (SB242084; 6 mg/kg, PO), or ghrelin enhancer (rikkunshito (RKT); 1000 mg/kg, PO) was administered to aged female mice immediately after stress exposure. Data are presented as the mean ± SEM, (A, B) young; fed n = 9, fasted n = 8, aged; fed n = 3, fasted n = 5, (C) young; n = 8, aged; n = 5, (D) n = 5. (A-C); *, p < 0.05, **, p < 0.01 vs. young control group, (D); #, p < 0.05 vs. distilled water (DW)-treated non-stressed group. *, p < 0.05 vs. DW-treated stressed group.</p

Influence of Aging and Gender Differences on Feeding Behavior and Ghrelin-Related Factors during Social Isolation in Mice

<div><p>Psychological stress due to social isolation is known to cause abnormal feeding behaviors, but the influences of gender and aging on subchronic stress-induced changes in feeding behaviors are unknown. Thus, we examined the changes in body weight, food intake, and orexigenic ghrelin-related factors during 2 weeks of isolation stress in young and aged mice. Food intake increased significantly in young mice in the isolation group compared with the group-housed control throughout the experimental period. This isolation-induced increase in food intake was not observed in aged mice. In young mice, there were no significant differences in body weight between the isolated group and group-housed control up to 2 weeks. However, aged male mice exhibited significant weight loss at 2 weeks and a similar tendency was observed in aged female mice. Young male mice, but not female mice, had significantly increased (2.2-fold) plasma acylated ghrelin levels after 1 week of isolation compared with the group-housed control. A significant but lower increase (1.3-fold) was also observed in aged male mice. Hypothalamic preproghrelin gene expression decreased significantly with isolation in young male mice, whereas it increased significantly in female mice. The expression levels of NPY and AGRP in the hypothalamus, which are transmitted by elevated peripheral ghrelin signals, increased significantly in isolated young male mice, whereas the AGRP expression levels decreased significantly in young female mice. Isolation caused no significant differences in the expression levels of these genes in aged mice. In isolation, young female mice exhibited markedly increased dark- and light-phase locomotor activities compared with male mice, whereas male and female aged mice exhibited no obvious increases in activity immediately after the dark phase started. We conclude that the gender-specific homeostatic regulatory mechanisms required to maintain body weight operated during subchronic psychological stress in young mice but not in aged mice.</p></div

Locomotor activity levels after 2 weeks of isolation.

<p>The 24-h locomotor activity levels are shown for group-housed young mice (A), isolated young mice (B), group-housing aged mice (C), and isolated aged mice (D), as well as quantitative data for the locomotor activity levels (E–H). The data represent the mean ± SEM (Young group: n = 5, Young isolation: n = 8–9, Aged group: n = 3, Aged isolation: n = 6–7). **, ***<i>p</i> < 0.01, 0.001 respectively vs. male mice.</p

Body weight and changes in body weight during 2 weeks of isolation.

<p>Two-way repeated measures factorial ANOVA of body weight in all groups detected no significant changes. In the young male and female mice, two-way repeated measures factorial ANOVA of body weight changes detected no effects of isolation in males [young male: F(1, 33) = 0.4245, n.s.; young female: F(1, 36) = 0.0507, n.s.], significant effects of time in males and females [young male: F(2, 33) = 4.3506, p < 0.05; young female: F(2, 36) = 9.4196, p < 0.001], but the isolation × time interaction effects [young male: F(2, 33) = 0.0247, n.s.; young female: F(2, 36) = 0.9639, n.s.] were not significant. In aged mice, there were significant effects of isolation in males [aged male: F(1, 21) = 7.9029, p < 0.05; aged female: F(1, 24) = 2.0955, n.s.], time in males [aged male: F(2, 21) = 3.9764, p < 0.05; aged female: F(2, 24) = 0.4656, n.s.], but the isolation × time interaction effects [aged male: F(2, 21) = 1.7366, n.s.; aged female: F(2, 24) = 0.2593, n.s.] were not significant. Body weights of young male mice (A), young female mice (B), aged male mice (C), and aged female mice (D) are shown. Changes in the body weights of young male mice (E), young female mice (F), aged male mice (G), and aged female mice (H) are shown. The data represent the mean ± SEM (Young group: n = 5, Young isolation: n = 8–9, Aged group: n = 3, Aged isolation: n = 6–7).*p < 0.05 vs. group-housed mice.</p

Food intake rates during 2 weeks of isolation.

<p>Two-way repeated measures factorial ANOVA of 24-h cumulative food intake in the young males and females detected significant effects of isolation [young male: F(1, 33) = 18.563, <i>p</i> < 0.001; young female: F(1, 36) = 7.9896, <i>p</i> < 0.01] and of time [young male: F(2, 33) = 3.6586, <i>p</i> < 0.05; young female: F(2, 36) = 20.315, <i>p</i> < 0.001], but the isolation × time interaction effects [young male: F(2, 33) = 0.0877, n.s.; young female: F(2, 36) = 2.7901, n.s.] were not significant. In aged mice, there were no significant effects of isolation [aged male: F(1, 22) = 4.1125, n.s.; aged female: F(1, 24) = 1.0384, n.s.] or of time [aged male: F(2, 22) = 1.8869, n.s.; aged female: F(2, 24) = 0.0923, n.s.], and isolation × time interaction effects [aged male: F(2, 22) = 1.1071, n.s.; aged female: F(2, 24) = 0.0793, n.s.] were not significant. The 24-h cumulative food intake rates in young male mice (A), young female mice (B), aged male mice (C), and aged female mice (D) are shown. The data represent the mean ± SEM (Young group: n = 5, Young isolation: n = 8–9, Aged group: n = 3, Aged isolation: n = 6–7). **, ***<i>p</i> < 0.01, 0.001 respectively vs. group-housed mice.</p

Changes in hypothalamic appetite-related peptide gene expression in aged male or female mice exposed to novelty stress.

<p>The 6 h hypothalamic appetite-related peptide in young and aged male mice (A), or female mice (B) exposed to novelty stress. Data are presented as the mean ± SEM (young male and aged female groups; n = 8, aged control female group; n = 7). ***, p < 0.001 vs. young control group. #, p < 0.05 vs. aged control group.</p

Experimental protocol employed in this study.

<p>Experimental protocol employed in this study.</p

Possible mechanisms for age- and gender-specific changes in feeding and locomotion after subchronic isolation.

<p>Possible mechanisms for age- and gender-specific changes in feeding and locomotion after subchronic isolation.</p

Effects of the 5-HT_2CR antagonist and the endogenous ghrelin enhancer on cumulative food intake and the plasma corticosterone level in aged female mice exposed to novelty stress.

<p>5-HT_2CR antagonists, SB242084 (6 mg/kg, PO) or RKT(1000 mg/kg, PO) was administered immediately after stress exposure. (A) Cumulative food intake (1 h and 3 h) and (B) plasma corticosterone levels (3 h) after stress exposure was determined in 18 h fasted aged female mice. Data are presented as the mean ± SEM (n = 5–10). ###, p < 0.001 vs. control group, ***, p < 0.001 vs. novelty stress group.</p