In histology, serotonin receptors are studied using various techniques such as immunohistochemistry, in situ hybridization, and autoradiography. These methods allow researchers to visualize the distribution and density of serotonin receptors in different tissues. Immunohistochemistry involves using antibodies that specifically bind to serotonin receptors, while in situ hybridization involves using labeled RNA probes to detect receptor mRNA. Autoradiography uses radiolabeled ligands to identify receptor-binding sites.