SignificancePrimary cilia are antenna-like organelles that represent a frontier of knowledge in neuroscience research. They were first reported by Duncan and Dahl more than 60 years ago, and although they are implicated in neurodevelopmental diseases, our understanding of their function in neurons is limited. In this manuscript, the authors demonstrate that the primary cilium is an excitable organelle richly populated with PKD2L1 ion channels. Using microelectrode electrophysiology and mouse genetics, the authors find that these channels in the cilia contribute to high-frequency action potential firing and their loss of function primarily impacts interneuron excitability. Loss of PKD2L1 expression impairs ciliary maturation in mice, which behaviorally exhibits autism-like features and seizure susceptibility that may have implications to human neuronal ciliopathy conditions.