Chronic exogenous corticosterone administration generates an insulin-resistant brain state in rats

Figures & data

Table I.  Rats' body weight and plasma CST levels.

	Rat body weight (g)		Plasma CST (μg/100 mL)
	T1	T2	T1	T2
Control		532 ± 45		20.1 ± 7.8
Placebo	576 ± 64	513 ± 44	15.4 ± 5.4	27.8 ± 10.4
CST		432 ± 51^*#		32.3 ± 8.4^*#

T1, before daily injections (n = 24); T2, after 60 days of daily injections (n = 8 per group). Data are expressed as mean ± SD. Significant differences (p < 0.05): ^*between CST- and placebo-treated/control groups; ^#between the CST group at T2 as compared to T1.

Figure 1  Working memory [(number of food rewarded visits/number of visits and revisits to the baited set of holes) × 100] and reference memory [(number of visits and revisits to the baited set of holes/number of visits and revisits to all holes) × 100] ratios were determined at the beginning and after the end of the CST-treatment and were calculated according to van der Staay et al. (1990). T1, before daily injections (n = 24), T2, after 60 days of daily injections (n = 8 per group). CST, corticosterone treatment. Data are expressed as mean ± SD. Significant differences (p < 0.05): ^*between CST-/placebo-treated and control groups (p = 0.008); ^#between the CST-group at T2 as compared to T1 (p = 0.018).

Figure 2  Normalized mRNA expression (means and SEM) for IR, insulin (ins) 1, insulin 2, and IDE in the cortex of CST-treated rats, vehicle-treated placebo rats (injection-stress group) and untreated control (stress-free group). Kruskal–Wallis ANOVA test, ^*p < 0.05, n = 8 per group. p(IR) = 0.025, p(Ins1) = 0.032, p(IDE) = 0.05.

Figure 3  Normalized total mRNA expression (means and SEM) for tau protein in rat cortex after 60 days of CST treatment as compared to vehicle-treated placebo rats (injection-stress group) and untreated control. Kruskal–Wallis ANOVA test ^*p < 0.05, n = 8 per group, p = 0.034.

van der Staay FJ, van Nies J, Raaijmakers W. 1990. The effects of aging in rats on working and reference memory performance in a spatial holeboard discrimination task. Behav Neural Biol. 53:356–370.

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