“Neuronal migration is a fundamental process of brain development, and its disruption underlies devastating neurodevelopmental disorders. The transcriptional programs governing this process are relatively well characterized. However, how environmental cues instruct neuronal migration remains poorly understood. Here, we demonstrate that the cannabinoid CB 1 receptor is strictly required for appropriate pyramidal neuron migration in the developing cortex. Acute silencing of the CB 1 receptor alters neuronal morphology and impairs radial migration. Consequently, CB 1 siRNA-electroporated mice display cortical malformations mimicking subcortical band heterotopias and increased seizure susceptibility in adulthood. Importantly, rescuing the CB 1 deficiency-induced radial migration arrest by knockdown of the GTPase protein RhoA restored the hyperexcitable neuronal network and seizure susceptibility. Our findings show that CB 1 receptor/RhoA signaling regulates pyramidal neuron migration, and that deficient CB 1 receptor signaling may contribute to cortical development malformations leading to refractory epilepsy independently of its canonical neuromodulatory role in the adult brain.”