CBD, Neuroprotection, and Neurogenesis

"There are various mechanisms underlying neuroprotection, for example, energy metabolism (whose alteration has been implied in several psychiatric disorders) and proper mitochondrial functioning.²⁴ An early study from 1976 found no side effects and no effect of 0.3–300 μg/mg protein CBD after 1 h of incubation on mitochondrial monoamine oxidase activity in porcine brains.²⁵ In hypoischemic newborn pigs, CBD elicited a neuroprotective effect, caused no side effects, and even led to beneficial effects on ventilatory, cardiac, and hemodynamic functions.²⁶

"A study comparing acute and chronic CBD administration in rats suggests an additional mechanism of CBD neuroprotection: Animals received i.p. CBD (15, 30, 60 mg/kg b.w.) or vehicle daily, for 14 days. Mitochondrial activity was measured in the striatum, hippocampus, and the prefrontal cortex.²⁷ Acute and chronic CBD injections led to increased mitochondrial activity (complexes I-V) and creatine kinase, whereas no side effects were documented. Chronic CBD treatment and the higher CBD doses tended to affect more brain regions. The authors hypothesized that CBD changed the intracellular Ca2+ flux to cause these effects. Since the mitochondrial complexes I and II have been implied in various neurodegenerative diseases and also altered ROS (reactive oxygen species) levels, which have also been shown to be altered by CBD, this might be an additional mechanism of CBD-mediated neuroprotection.^1,27

"Interestingly, it has recently been shown that the higher ROS levels observed after CBD treatment were concomitant with higher mRNA and protein levels of heat shock proteins (HSPs). In healthy cells, this can be interpreted as a way to protect against the higher ROS levels resulting from more mitochondrial activity. In addition, it was shown that HSP inhibitors increase the CBD anticancer effect in vitro.²⁸ This is in line with the studies described by Bergamaschi et al., which also imply ROS in CBD effect on (cancer) cell viability in addition to, for example, proapoptotic pathways such as via caspase-8/9 and inhibition of the procarcinogenic lipoxygenase pathway.¹

"Another publication studied the difference of acute and chronic administration of two doses of CBD in nonstressed mice on anxiety. Already an acute i.p. administration of 3 mg/kg was anxiolytic to a degree comparable to 20 mg/kg imipramine (an selective serotonin reuptake inhibitor [SSRI] commonly prescribed for anxiety and depression). Fifteen days of repeated i.p. administration of 3 mg/kg CBD also increased cell proliferation and neurogenesis (using three different markers) in the subventricular zone and the hippocampal dentate gyrus. Interestingly, the repeated administration of 30 mg/kg also led to anxiolytic effects. However, the higher dose caused a decrease in neurogenesis and cell proliferation, indicating dissociation of behavioral and proliferative effects of chronic CBD treatment. The study does not mention adverse effects.¹⁹"