A new study on mice gives credence to the theory that long-term exposure of low dosages of THC improves cognitive performance in aging animals while decreasing it in very young mice. The authors of the study, Bilkei-Gorzo, et al, demonstrated that THC increases the density of hippocampal synapses. The hippocampus is the region of the brain linked to cognitive performance. Evidence supports that chronic THC exposure in aged animals induced the generation of synaptic proteins similar to levels seen in young mice. The researchers attribute this effect to signaling through CB1 receptors. CB1 receptors are expressed mainly in the brain (central nervous system or CNS) but also in the lungs, liver and kidney.
THC also increased phosphorylation, critical for many cellular processes to occur, of signaling proteins which support learning and memory. Lastly, THC increases the levels of histone acetylation, an essential part of gene regulation, in the hippocampus. The authors pinpointed three genes that are linked to life span, cognitive modulation and synaptic plasticity; klotho, transthyretin and brain-derived neurotrophic factor (BDNF). THC causes them to be upregulated which is the increase of a cellular component. Two other genes, connective tissue growth factor and caspase 1, which regulate pro-aging processes, are downregulated by THC exposure. Downregulation is the cellular decrease in the number of receptors to a molecule, such as a hormone or neurotransmitter, which reduces the cell’s sensitivity to the molecule.
The secondary question raised by the study has to do with other cannabinoids in the cannabis plant. THC activates CB1 receptors as well as some less abundant cannabinoid receptors. Would Cannabis Sativa preparations be as beneficial as THC in improving cognitive function in the aging brain? More complementary studies could answer that question. As the human life span increases worldwide, finding a solution to promote healthy aging is becoming more and more crucial, both socially and economically.
Source: Bilkei-Gorzo, A. et al Nat. Med. 23, 782-787 (2017)