Effects of eicosapentaenoic acid and docosahexaenoic acid on anxiety-like behavior in socially isolated rats

Figures & data

Table 1. Composition of the diets (g/100 g of diet).

			CON	EPA	DHA
α-Cornstarch			43.67	43.67	43.67
Sucrose			21.83	21.83	21.83
Cellulose			5	5	5
Casein			20	20	20
AIN93G mineral mixture			3.5	3.5	3.5
AIN93 vitamin mixture			1	1	1
Corn oil			5	2	2
EPA-40			0	3	0
DHA-46			0	0	3
α-tocopherol			0.015	0	0.006
Total			100.0	100.0	100.0
Fatty acid composition (%)
14:0		Myristoleic acid		2.6	1.1
16:0		Palmitic acid	11.2	7.7	10.8
16:1	n-7	Palmitoleic acid		4.9	2.1
18:0		Stearic acid	1.2	1.5	2.1
18:1	n-9	Oleic acid	31.6	17.4	20.5
18:2	n-6	Linoleic acid	55.5	25.8	23.8
18:3	n-3	α-linolenic acid	0.5	0.8	1.7
20:4	n-6	Arachidonic acid		1.5	2.7
20:5	n-3	Eicosapentaenoic acid		27.3	4.2
22:5	n-3	Docosapentaenoic acid		2.5	1.5
22:6	n-3	Docosahexaenoic acid		8.0	29.5
Total			100	100	100

Alpha-tocopherol was added to CON and DHA to make total α-tocopherol contents of all diets same.

Figure 1. Performance in the elevated plus maze test. Open-arm time (A), open-arm frequency (B), head-dipping time (C), head-dipping frequency (D), stretch-out time (E), stretch-out frequency (F), locomotion time (G), and locomotion frequency (H) in rats fed control (CON), eicosapentaenoic acid-enriched (EPA), or docosahexaenoic acid-enriched (DHA) diets.

Values are presented as mean + SEM (n = 6 per group). *p < 0.05; **p < 0.01 vs. CON.

Figure 2. Performance in the open-field test. Center area time (A), center area frequency (B), supported rearing time (C), supported rearing frequency (D), unsupported rearing time (E), unsupported rearing frequency (F), grooming time (G), grooming frequency (H), locomotion time (I), locomotion frequency (J) of the rats fed control (CON), eicosapentaenoic acid-enriched (EPA), or docosahexaenoic acid-enriched (DHA) diets.

Values are presented as mean + SEM (n = 6 per group). *p < 0.05; ** p < 0.01 vs. CON.

Table 2. EPA and DHA contents in the phospholipid fraction of the cerebral cortex (%).

			CON	EPA	DHA
20:5	n-3	Eicosapentaenoic acid	ND	0.22 ± 0.03	0.11 ± 0.02
22:6	n-3	Docosahexaenoic acid	12.30 ± 0.61	14.34 ± 0.58*	14.90 ± 0.52*

ND: not detected.

* p < 0.05.

Figure 3. Performance in the elevated plus maze test. Open-arm time (A), open-arm frequency (B), head-dipping time (C), head-dipping frequency (D), stretch-out time (E), stretch-out frequency (F), locomotion time (G), locomotion frequency (H) of the rats fed control (CON) or eicosapentaenoic acid-enriched (EPA) diets, and group-housed (group) or individually housed (i.e. isolated).

Values are presented as mean + SEM (n = 6 per group). Result of two-way ANOVA is shown below each graph (NS, not significant; *p < 0.05; **p < 0.01). Turkey’s test was further conducted when a significant diet × housing interaction was observed by two-way ANOVA. Different letters above the bars indicate statistically significant differences.

Figure 4. Performance in the open-field test. Center area time (A), center area frequency (B), supported rearing time (C), supported rearing frequency (D), unsupported rearing time (E), unsupported rearing frequency (F), grooming time (G), grooming frequency (H), locomotion time (I), and locomotion frequency (J) of the rats fed control (CON) or eicosapentaenoic acid-enriched diet (EPA) and group-housed (group) or individually housed (i.e. isolated).

Values are presented mean + SEM (n = 6 per group). Results of two-way ANOVA is shown below each graph (NS, not significant; *p < 0.05; **p < 0.01).

Table 3. Fatty acid composition of the cerebral cortex (%).

		Total Lipid		Phospholipid
Fatty acids		CON	EPA	CON	EPA
14:0		0.68 ± 0.02	0.57 ± 0.06	0.22 ± 0.02	0.22 ± 0.03
16:0		26.28 ± 0.51	25.17 ± 1.14	29.99 ± 1.56	30.60 ± 0.59
18:0		13.30 ± 0.30	12.56 ± 0.36	14.75 ± 0.57	14.63 ± 0.40
18:1	n-9	11.52 ± 0.29	13.64 ± 0.76*	26.37 ± 2.88	26.24 ± 1.16
18:2	n-6	1.48 ± 0.03	1.64 ± 0.09	0.69 ± 0.24	0.61 ± 0.06
20:1	n-9	1.94 ± 0.09	2.25 ± 0.45	0.32 ± 0.08	0.30 ± 0.08
20:3	n-6	1.93 ± 0.06	1.95 ± 0.09	0.44 ± 0.04	0.42 ± 0.01
20:4	n-6	13.95 ± 0.24	11.46 ± 0.37**	11.27 ± 0.76	9.54 ± 0.20
20:5	n-3	2.56 ± 0.03	2.93 ± 0.19^p = 0.074	0.12 ± 0.04	0.48 ± 0.02**
22:4	n-6	4.33 ± 0.03	4.19 ± 0.20	1.65 ± 0.12	1.32 ± 0.03*
22:5	n-6	3.78 ± 0.06	ND	0.38 ± 0.05	0.05 ± 0.02**
22:5	n-3	ND	3.83 ± 0.06	0.02 ± 0.02	0.30 ± 0.04**
22:6	n-3	18.24 ± 0.77	19.81 ± 0.55	13.78 ± 1.07	15.29 ± 0.41

Fatty acid composition in the total lipid fraction and phospholipid fraction of the cerebral cortex of the rats fed control (CON) or eicosapentaenoic acid-enriched diet (EPA).

Values are the means ± SEM (n = 6).

ND: not detected.

* p < 0.05.

** p < 0.01.