Persistent inhibitory circuit defects and disrupted social behavior following in utero exogenous cannabinoid exposure

Placental transfer of Δ9-tetrahydrocannabinol (THC) during pregnancy has the potential to interfere with endogenous cannabinoid regulation of fetal nervous system development in utero. Here we examined the effect of maternal cannabinoid intake on mouse hippocampal interneurons largely focusing on cholecystokinin containing interneurons (CCK-INTs), a prominent cannabinoid subtype 1 receptor (CB1R) expressing neuronal population throughout development. Maternal treatment with THC or the synthetic CB1R agonist WIN55,212-2 (WIN) produced a significant loss of CCK-INTs in offspring. Further, residual CCK-INTs in animals prenatally treated with WIN displayed decreased dendritic complexity. Consistent with these anatomical deficits, pups born to cannabinoid treated dams exhibited compromised CCK-INT mediated feedforward and feedback inhibition. Moreover, pups exposed to WIN in utero lacked constitutive CB1R mediated suppression of inhibition from residual CCK-INTs, and displayed altered social behavior. Our findings add to a growing list of potential cell/circuit underpinnings that may underlie cognitive impairments in offspring of mothers that abuse marijuana during pregnancy.