Prenatal THC exposure reduced NPY neurons specifically in female rat hippocampus, while combined THC and alcohol exposure affected additional brain regions.
Female-specific NPY decreaseOnly female offspring showed reduced NPY neuron density in the CA1 region after prenatal THC exposure
What the researchers found
Prenatal THC exposure had region-specific and sex-specific effects on inhibitory interneurons in the hippocampus:
- Female-specific decrease in NPY neuron density in the CA1 region after THC exposure
- Somatostatin neurons were altered by THC in a region-specific and sex-specific manner
- Combined alcohol + THC: reduced NPY neurons in the ventral dentate gyrus
- Co-exposure did NOT produce additive or synergistic effects in other hippocampal areas
These findings build on the group's previous work showing prenatal substance exposure alters parvalbumin interneurons, extending the picture to two additional inhibitory cell types.
Why it matters
Cannabis use during pregnancy is increasing as legalization spreads. The hippocampus is critical for memory and emotional regulation. If prenatal THC disrupts inhibitory interneurons (NPY and somatostatin neurons), it could impair the brain's ability to regulate neural activity, potentially contributing to learning, memory, and mood problems in offspring.
The numbers in context
- Exposure period: gestational days 5-20
- Analysis at: postnatal day 70
- NPY decrease: female CA1 region (THC exposure)
- NPY decrease: ventral dentate gyrus (combined THC + alcohol)
- Somatostatin: region-specific and sex-specific changes with THC
- No additive/synergistic effects in most hippocampal areas
How the study worked
2 × 2 design: pregnant Sprague-Dawley rats exposed to ethanol or air AND THC or vehicle during gestational days 5-20. Offspring were sacrificed at postnatal day 70. Immunohistochemistry for somatostatin and NPY neurons was performed on 50 μm hippocampal tissue sections.
Who was studied
Offspring of Sprague-Dawley rats exposed to THC, ethanol, both, or neither during pregnancy, analyzed at postnatal day 70
What this study cannot tell us
This was tested in rats. Human prenatal cannabis exposure involves different doses, timing, and genetic backgrounds. THC was given by inhalation, which may not exactly match human smoking patterns. The study measured neuron density at one time point (day 70), not developmental trajectory. Behavioral consequences of the interneuron changes were not tested. The 2×2 design had limited power for detecting interaction effects.
How to read the evidence
Rated preliminary: well-designed factorial animal study but findings are in rats and may not directly translate to human prenatal exposure.
When this study was published
Published in 2024. Highly relevant as cannabis legalization increases prenatal exposure rates globally.
The bigger picture
Cannabis use during pregnancy is increasing with legalization. The hippocampus is critical for memory and emotional regulation. Disrupting inhibitory interneurons could contribute to the cognitive and psychiatric problems observed in prenatally exposed children.
Questions still open
- Do these interneuron changes lead to functional cognitive deficits?
- Are female offspring more vulnerable to prenatal THC exposure?
Common questions
Does cannabis during pregnancy affect the baby's brain?
Is the combination of cannabis and alcohol worse?
Read the original research
Prenatal ethanol and cannabis exposure have sex- and region-specific effects on somatostatin and neuropeptide Y interneurons in the rat hippocampus.
Alcohol, clinical & experimental research, 48(7), 1289-1301
Citation
Reid, Hannah M O; Trepanier, Owen; Gross, Allyson; Poberezhnyk, Polina; Snowden, Taylor; Conway, Kate; Breit, Kristen R; Rodriguez, Cristina; Thomas, Jennifer D; Christie, Brian R. (2024). Prenatal ethanol and cannabis exposure have sex- and region-specific effects on somatostatin and neuropeptide Y interneurons in the rat hippocampus.. Alcohol, clinical & experimental research, 48(7), 1289-1301. https://doi.org/10.1111/acer.15350