Adult Hippocampal Neurogenesis Is a Different Outcome From Neuronal Survival
An intervention that changes the production of new hippocampal neurons has not necessarily changed the survival of existing neurons. A review of alcohol–endocannabinoid research illustrates why these outcomes need separate descriptions.
The experiment concerned adult neurogenesis
Kunos’s 2020 review describes Wistar-rat experiments in which a CB1 agonist or an inhibitor of endocannabinoid degradation mimicked alcohol’s inhibition of adult hippocampal neurogenesis. CB1 antagonists prevented the alcohol-associated inhibition.
These comparisons support a contribution from cannabinoid signaling to the measured process. They concern experimental manipulation of the system, not a demonstration that ordinary cannabis exposure produces the same result in adult human brains.
Reduced production does not establish cell death
Neurogenesis concerns the generation of new neurons. A reduction in that process should not be reported as proof that previously existing neurons died. Conversely, preservation of existing cells would not automatically establish restoration of new-neuron production.
Likewise, a change in this biological outcome does not directly quantify memory, mood or day-to-day functioning. Connecting it to a behavioral consequence requires measurements that address that consequence.
Interpret the blocker result within its scope
Preventing the measured inhibition with a CB1 antagonist helps test a receptor mechanism. It does not establish that giving a blocker is a safe or effective way to protect the human brain, and it does not identify a clinical benefit without clinical outcomes.
For research interpretation, identify whether the evidence measured proliferation, neuronal differentiation, survival or behavior. Keeping these outcomes distinct preserves the mechanistic value of the animal findings while avoiding a broader claim of neuroprotection or brain damage than the experiment supports.
Related reading: A CB1 Role in Developmental Alcohol Injury Was Not a Cannabis-Exposure Experiment.
Research cited
Kunos G. Interactions Between Alcohol and the Endocannabinoid System (2020). This analysis draws on the review’s discussion of the cited experiments.
