THC Changed How the Hippocampus Communicates in Female Rats, Depending on Estrogen
THC altered cholinergic, glutamatergic, and GABAergic neurotransmission in the hippocampus of female rats, with effects that varied depending on whether estrogen was present, suggesting sex hormones shape how THC affects the brain.
Quick Facts
What This Study Found
In the hippocampus of ovariectomized female rats, THC increased cholinergic receptor (CHRNA7), glutamate transporter (VGLUT), and GABA receptor expression when estrogen was absent, but decreased these same markers when estrogen was present. THC also increased CB1 receptor and acetylcholine transporter expression that had been reduced by estrogen.
Key Numbers
N=20 female Wistar rats; hippocampal subregions CA1, CA3, DG, hilum examined; 6 neurotransmitter markers assessed; estrogen reversed the direction of THC effects on multiple markers.
How They Did This
Twenty female Wistar rats were ovariectomized at 8 weeks and received estradiol benzoate and/or THC. Immunohistochemistry assessed expression of cholinergic (CHRNA7, VAChT), glutamatergic (VGLUT), GABAergic (GABRA, GAD), cannabinoid (CB1), and estrogen (ERalpha) receptors across hippocampal subregions (CA1, CA3, DG, hilum).
Why This Research Matters
Most cannabis research uses male animals, leaving a gap in understanding how THC affects the female brain. This study reveals that estrogen status fundamentally changes how THC interacts with hippocampal neurotransmission, which has implications for understanding sex differences in cannabis effects on memory and cognition.
The Bigger Picture
This study contributes to growing evidence that sex hormones modulate cannabinoid effects on the brain. Given that the hippocampus is critical for memory formation, these findings may help explain why some studies find different cognitive effects of cannabis in women versus men.
What This Study Doesn't Tell Us
Small animal sample size (N=20). Ovariectomized rats receiving exogenous estrogen do not fully replicate natural hormonal cycling. Results from rat hippocampus may not directly translate to human neurobiology. Does not assess behavioral or cognitive outcomes of the observed neurochemical changes.
Questions This Raises
- ?Do these estrogen-dependent effects of THC translate to cognitive differences in humans?
- ?How do natural hormonal cycles (menstrual cycle, menopause) affect cannabis sensitivity?
- ?Should THC dosing recommendations differ based on hormonal status?
Trust & Context
- Key Stat:
- Estrogen reversed the direction of THC's effects on hippocampal neurotransmission in female rats
- Evidence Grade:
- Preliminary: Small animal study (N=20) providing mechanistic insights that require validation in larger studies and, ultimately, human research.
- Study Age:
- Published in 2025.
- Original Title:
- Exogenous Administration of Delta-9-Tetrahydrocannabinol Affects Adult Hippocampal Neurotransmission in Female Wistar Rats.
- Published In:
- International journal of molecular sciences, 26(13) (2025)
- Authors:
- Neves, Ana M, Leal, Sandra, Fonseca, Bruno M(4), Sá, Susana I
- Database ID:
- RTHC-07246
Evidence Hierarchy
Tests effects in animals (usually mice or rats), not humans.
What do these levels mean? →Frequently Asked Questions
Why does estrogen matter for cannabis effects?
Estrogen and the endocannabinoid system interact extensively. This study showed that the same dose of THC had opposite effects on hippocampal neurotransmitter markers depending on whether estrogen was present, suggesting that hormonal status fundamentally shapes how cannabis affects the brain.
Could this explain why cannabis affects men and women differently?
Potentially. The hippocampus is critical for memory, and sex differences in cannabis-related cognitive effects have been reported in human studies. This animal research suggests that sex hormones like estrogen may be a key factor in those differences.
Read More on RethinkTHC
- THC-amygdala-anxiety-brain
- anandamide-weed-withdrawal
- cannabinoid-receptors-recovery-time
- cannabis-developing-brain-teenagers
- cant-enjoy-anything-without-weed
- dopamine-recovery-after-quitting-weed
- endocannabinoid-system-explained-simply
- endocannabinoid-system-withdrawal
- nervous-system-weed-withdrawal-fight-flight
- teen-weed-use-under-18-effects-brain
- thc-brain-withdrawal
- thc-prefrontal-cortex-brain-effects
- weed-cortisol-stress-hormones
- weed-memory-loss-recovery
- weed-motivation-amotivational-syndrome
- weed-nervous-system-effects
- weed-reward-system-brain
Cite This Study
https://rethinkthc.com/research/RTHC-07246APA
Neves, Ana M; Leal, Sandra; Fonseca, Bruno M; Sá, Susana I. (2025). Exogenous Administration of Delta-9-Tetrahydrocannabinol Affects Adult Hippocampal Neurotransmission in Female Wistar Rats.. International journal of molecular sciences, 26(13). https://doi.org/10.3390/ijms26136144
MLA
Neves, Ana M, et al. "Exogenous Administration of Delta-9-Tetrahydrocannabinol Affects Adult Hippocampal Neurotransmission in Female Wistar Rats.." International journal of molecular sciences, 2025. https://doi.org/10.3390/ijms26136144
RethinkTHC
RethinkTHC Research Database. "Exogenous Administration of Delta-9-Tetrahydrocannabinol Aff..." RTHC-07246. Retrieved from https://rethinkthc.com/research/neves-2025-exogenous-administration-of-delta9tetrahydrocannabinol
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.