Does turning down orexin make stressed rats resilient?
Rats that actively coped with social defeat had lower prepro-orexin mRNA; inhibiting lateral-hypothalamic orexin neurons with DREADDs on days 6–8 boosted social interaction and reduced forced-swim immobility in previously passive, vulnerable rats.
Source
Reduced Orexin System Function Contributes to Resilience to Repeated Social Stress
Study at a glance
- Design
- Animal / in-vitro — Rat resident-intruder social defeat with in situ/qPCR of prepro-orexin, then orexin-targeted hM4Di DREADDs + CNO on days 6–8
- N
- N=12 · Key in situ after DREADDs+behavior n=12/group; several ANOVAs n=6/group; phenotypes split by defeat latency over 5–7 days
- Population
- Male rats classified as passive vs active copers during repeated social defeat by Long-Evans residents (plus non-defeated controls)
- Outcome
- Prepro-orexin mRNA; social interaction; forced-swim immobility after inhibiting orexin neurons
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Inspect source passages
Does turning down orexin make stressed rats resilient?
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
CNO after FST: F(1,38)=8.0, p=0.007 on prepro-orexin.
CNO effect, F (1,38) = 8.0, p = 0.007
Passive copers average latency <300 s.
Passively coping rats have an average defeat latency <300 s
What they did
Used 5–7 days of resident-intruder defeat to split passive (<300 s latency) vs active copers, measured lateral-hypothalamic prepro-orexin by in situ/qPCR, then expressed hM4Di in orexin neurons and injected CNO (2 mg/kg) before defeats on days 6–8, followed by social interaction and a 2-day Porsolt FST.
What they found
Active copers expressed significantly less prepro-orexin mRNA than passive copers. CNO inhibition increased social interaction and decreased depressive-like behavior in the vulnerable group, bringing passive copers toward active-coper interaction times. After FST, CNO lowered prepro-orexin (F(1,38)=8.0, p=0.007).
The limits
What it doesn't show
Male-rat DREADDs at 2 mg/kg CNO do not prove orexin antagonists treat human PTSD/depression; effects were phenotype-specific and not a general activity increase.
Key terms
- Orexins (hypocretins)
- Lateral-hypothalamic neuropeptides for arousal and stress; lower levels tracked resilience here.
- Social defeat
- Resident-intruder stress; latency to be defeated clustered rats into passive vs active copers.
- Passive coping
- Short defeat latency (<300 s) associated with later anxiety/depressive-like behavior.
- DREADDs
- Designer receptors (here Gi-coupled hM4Di) activated by CNO to inhibit orexin neurons.
- CNO
- Clozapine-N-oxide, 2 mg/kg i.p. 60 min before defeat on days 6–8.
- Forced swim test (FST)
- Porsolt assay of depressive-like immobility (15 min day 1, 5 min day 2).
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Resilient active copers had:
Common questions
Who had lower orexin mRNA?
Actively coping (resilient) rats vs passive copers.
Passive-coper latency?
Average defeat latency <300 s.
What did DREADD inhibition do?
More social interaction and less FST immobility in vulnerable rats.
CNO dose?
2 mg/kg before each of the last 3 defeat days.
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