Cannabinoids promote embryonic and adult hippocampus neurogenesis and produce anxiolytic- and antidepressant-like effects
Wen Jiang, Yun Zhang, Lan Xiao, Jamie Van Cleemput, Shao-Ping Ji, Guang Bai and Xia Zhang
J Clin Invest. 2005;115(11):3104–3116. doi:10.1172/JCI25509.
The hippocampal dentate gyrus in the adult mammalian brain contains neural stem/progenitor cells (NS/PCs) capable of generating new neurons, i.e., neurogenesis. Most drugs of abuse examined to date decrease adult hippocampal neurogenesis, but the effects of cannabis (marijuana or cannabinoids) on hippocampal neurogenesis remain unknown. This study aimed at investigating the potential regulatory capacity of the potent synthetic cannabinoid HU210 on hippocampal neurogenesis and its possible correlation with behavioral change. We show that both embryonic and adult rat hippocampal NS/PCs are immunoreactive for CB1 cannabinoid receptors, indicating that cannabinoids could act on CB1 receptors to regulate neurogenesis. This hypothesis is supported by further findings that HU210 promotes proliferation, but not differentiation, of cultured embryonic hippocampal NS/PCs likely via a sequential activation of CB1 receptors, Gi/o proteins, and ERK signaling. Chronic, but not acute, HU210 treatment promoted neurogenesis in the hippocampal dentate gyrus of adult rats and exerted anxiolytic- and antidepressant-like effects. X-irradiation of the hippocampus blocked both the neurogenic and behavioral effects of chronic HU210 treatment, suggesting that chronic HU210 treatment produces anxiolytic- and antidepressant-like effects likely via promotion of hippocampal neurogenesis.
In layman's terms, this suggests that long-term, high dose cannabinoid usage may not be as unhealthy as previously thought. It is commonly believed thatthe hippocampus is a critical part of memory formation - if cannabinoids are promoting cell growth there, how can we explain memory loss?
It is also interesting to note that such a potent cannabinoid (HU210) is actually antidepressant-like at high doses, as long as you have some modicum of tolerance it seems.