LAUSR

Significance One of the most important morphological properties in the cerebral cortex is the columnar structure, where axonal projections occur precisely within individual vertical columns. However, how such precise axonal projections arise during development is not well known. Previous studies indicate that columnar topographical axonal projections are achieved by selective addition of axons within individual columns without identifying the molecule involved in this process. We show that the endocannabinoid is crucial for shaping columnar axonal projections of layer 4 neurons in the mouse barrel cortex by using mice with global knockout of the synthetic enzyme of the endocannabinoid 2-arachidonoylglycerol, pharmacological activation of type 1 cannabinoid receptor (CB1R), and knockout of CB1R in layer 4 neurons.