An opioid receptor antagonist given after stroke significantly improved blood pressure, EEG recovery, and neurological status compared to saline controls.
Improved EEG and neurological statusWith opioid antagonist at 24 hours after experimental stroke
What the researchers found
After middle cerebral artery occlusion (a stroke model) in rats, the opioid antagonist WIN at doses of 0.4 to 400 micrograms/kg produced several benefits.
All WIN doses significantly increased mean arterial blood pressure compared to saline controls. At the optimal dose of 40 micrograms/kg, rats showed significantly greater EEG (brain wave) recovery and higher neurological scores at 24 hours compared to controls.
Neurological outcome correlated with brain wave recovery on the injured side, confirming the measures tracked together.
However, 24-hour mortality and infarct (dead tissue) size were not significantly different from controls. The drug improved functional recovery without reducing the actual area of brain death.
At 1 hour after stroke, there were no significant changes in dynorphin, enkephalin, or endorphin levels in the injured vs. uninjured brain hemisphere. This was unexpected given the changes seen in trauma models.
Why it matters
This was one of the first dose-ranging studies of an opioid antagonist for stroke. The finding of functional improvement without infarct size reduction suggested opioid blockers may protect brain function in the penumbra (the at-risk zone around the dead tissue) rather than preventing cell death outright.
How the study worked
Rats received middle cerebral artery occlusion. WIN was given at 15 min, 3 hr, and 6 hr post-occlusion at doses from 0.4 to 400 micrograms/kg. Outcomes: blood pressure, EEG recovery, neurological scores, mortality, and infarct size at 24 hours. Opioid peptide levels measured at 1 hour. Tested in rats, not people.
What this study cannot tell us
Tested in rats, not people. The stroke model (complete artery occlusion) differs from most human strokes. The lack of opioid changes at 1 hour may reflect poor timing (too early or too late). Only one time point for peptide measurement. Functional improvement without infarct reduction raises questions about durability.
How to read the evidence
Moderate animal study with dose-response data and multiple outcome measures.
When this study was published
Published in 1988 — contributed to interest in neuroprotective strategies for stroke.
The bigger picture
Stroke treatment has a narrow time window. If opioid blockers can reduce secondary damage, they could extend the treatment window and improve outcomes alongside clot-busting drugs.
Questions still open
- What is the optimal dose and timing for opioid blockers after stroke?
- Would combination with standard stroke treatments enhance outcomes?
Common questions
How do opioid peptides contribute to stroke damage?
Could this lead to a new stroke treatment?
Read the original research
Levels of endogenous opioids and effects of an opiate antagonist during regional cerebral ischemia in rats.
The Journal of pharmacology and experimental therapeutics, 247(3), 1248-54
Citation
Andrews, B T; McIntosh, T K; Gonzales, M F; Weinstein, P R; Faden, A I. (1988). Levels of endogenous opioids and effects of an opiate antagonist during regional cerebral ischemia in rats.. The Journal of pharmacology and experimental therapeutics, 247(3), 1248-54.