Update in the methodology of the chronic stress paradigm: internal control matters

Table 2 Physiological correlates of stress and stress-induced anhedonia in our model

Physiological variable	Anhedonic Changes vs. control	Non-anhedonic Changes vs. control	Reference
1. Floating in forced swim test	Increased	Not changed	[38, 44, 45]
2. Immobilization in tailsuspension test	Increased	Not changed	[39, 47]
3. Novelty exploration	Decreased	Not changed	[44]
4. Burrowing behaviour	Decreased	Increased	[38, 39]
5. Contextual memory in passive avoidance	Decreased	Not changed	[38]
6. Contextual fear conditioning	Decreased	Not changed	[Tokarski et al. Impaired hippocampal plasticity in mice with hedonic deficit, induced by chronic stress (unpublished)]
7. LTP in the CA1 area of the hippocampus	Disrupted	Not changed	[Tokarski et al. Impaired hippocampal plasticity in mice with hedonic deficit, induced by chronic stress (unpublished)]
8. REM sleep	Increased	Not changed	[46, 48]
9. Home cage activity during dark phase	Increased	Not changed	[47]
10. Anxiety-like behavior in O-maze and dark-light box	Increased	Increased	[38, 44, 108]
11. Open field locomotion under modest lighting	Increased	Increased	[38, 44, 108]
12. Aggressive behavior	Increased	Increased	[[95], unpublished data]
13. Auditory fear conditioning	Not changed	Not changed	[Tokarski et al. Impaired hippocampal plasticity in mice with hedonic deficit, induced by chronic stress (unpublished]
14. Body weight	Decreased	Decreased	[38, 39, 44–49]

Eight out of fourteen evaluated physiological variables had differential changes in anhedonic and non-anhedonic animals, as compared to control. Remaining parameters were either not altered in these groups, or were changed in the same direction, suggesting that not all physiological consequences of stress can be attributed to anhedonia in the employed model.

ISSN: 1744-9081