The primary cilium is a sensory organelle found on most cells. In the brain, most or all neurons contain a single primary cilium, yet its function is not entirely understood. Ciliopathies are defined as a group of disorders physiologically characterized by malformation or dysfunction of primary cilia, which in turn result in a variety of symptoms including cognitive deficits, retinal blindness, situs inversus and polydactyly. The serotonin 6 receptor (5-HT6) is the only 5-HT receptor that localizes to neuronal primary cilia, and previous research has implemented the receptor in learning, memory, and drug addiction. Our experiment will investigate the link between neuronal primary cilia and 5-HT6 in an attempt to better understand the significance of this unique localization. Using an immortalized line of rat adrenal cells (PC12), we will express the 5-HT6 receptor using viral vectors, and then pharmacologically manipulate the activity of the receptors with either an agonist (WAY 399885) or an antagonist (SB 208466). We will first stain the cells using immunohistochemistry, then image using florescence microscopy, and lastly quantify the morphological change in primary cilia length. We expect to see a shortening of primary cilium in response to the introduction of an antagonist, and an increase in length with an agonist. Since the 5-HT6 receptor has been shown to be homologous between rats and humans, a practical application of this research could eventually result in a pharmaceutical solutions to some of the cognitive symptoms associated with ciliopathies like congenital cerebellar ataxia or Joubert syndrome.