BACKGROUND

Adolescent-onset cannabis use confers higher risk for neuropsychiatric disorders, implicating amygdala dysfunction. However, the mechanisms that mediate Δ-tetrahydrocannabinol (THC)-triggered neuroadaptive changes in the maturing amygdala remain unclear.

METHODS

Proteomic analysis of amygdala tissue from male adolescent nonhuman primates chronically treated with THC provided leads for targeted analyses of glial fibrillary acidic protein (GFAP), stathmin-1, and neuronal cell adhesion molecule (NrCAM) in a second species of male adolescent (postnatal day [P]35) and adult (P70) Sprague-Dawley rats. Primate activity monitoring and rat behavioral testing revealed THC-disrupted sleep architecture and anxiety-related behavior, respectively. Primary rat astrocyte cultures provided mechanistic insight into THC activation of astrocyte inflammatory function.

RESULTS

THC-induced upregulation of GFAP and complement factor-B (CF-B) signified proinflammatory glial activation exclusively in the adolescent amygdala, an effect absent in other brain regions and in adults. THC attenuated synaptic plasticity enhancers, stathmin-1 and NrCAM, effects not recapitulated in adults. Co-administered cannabidiol (CBD) prevented astrogliosis but did not restore synaptic plasticity marker levels. Astrogliosis was correlated with fragmented sleep, and attenuated plasticity markers were correlated with anxiety. THC-induced GFAP and CF-B upregulation with attenuation by CBD were replicated in cultured astrocytes, requiring cannabinoid type 1 receptor (CB1R)-activated calcium signaling. Elevated CB1R expression in the maturing brain was astrocyte-localized in the amygdala, but neuronal in the cortex and striatum.

CONCLUSIONS

Brain region- and age-specific regulation of CB1R in astrocytes critically links THC and unique adolescent amygdala vulnerability to inflammatory gliosis, impairing behaviors implicated in neuropsychiatric disorders. Mitigation of specific THC-induced changes by CBD offers leads for attenuating some adverse effects of THC.