Cannabidiol counteracts the psychotropic side-effects of δ-9-tetrahydrocannabinol in the ventral hippocampus through bi-directional control of ERK1-2 phosphorylation

Authors: Roger Hudson, Justine Renard, Christopher Norris, Walter J. Rushlow, Steven R. Laviolette


Evidence suggests that the phytocannabinoids Δ-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) differentially regulate salience attribution and psychiatric risk. The ventral hippocampus (vHipp) relays emotional salience via control of dopamine (DA) neuronal activity states, which are dysregulated in psychosis and schizophrenia. Using in-vivo electrophysiology in male Sprague Dawley rats, we demonstrate that intra-vHipp THC strongly increases ventral tegmental area (VTA) DA neuronal frequency and bursting rates, decreases GABA frequency, and amplifies VTA beta, gamma and epsilon oscillatory magnitudes via modulation of local extracellular signal-regulated kinase phosphorylation (pERK1-2). Remarkably, whereas intra-vHipp THC also potentiates salience attribution in morphine place-preference and fear conditioning assays, CBD co-administration reverses these changes by down-regulating pERK1-2 signaling, as pharmacological re-activation of pERK1-2 blocked the inhibitory properties of CBD. These results identify vHipp pERK1-2 signaling as a critical neural nexus point mediating THC-induced affective disturbances and suggest a potential mechanism by which CBD may counteract the psychotomimetic and psychotropic side-effects of THC.

Source: The Journal of Neuroscience, 2019; 0708-19