Figure 3: Serotonin main signaling pathways. 5-HT or agonists/antagonists for each receptor (•) interact in the extracellular side and the conformational changes of 5-HTRs modify the activity of specific intracellular enzymes, which in time modify other targets state to provoke different cellular responses [43]. G-protein βγ pathways are not represented in the figure. All of the serotonin receptor subtypes are represented for a hippocampal pyramidal cell, as reported, but subpopulations of these neurons might differentially express 5-HT receptors. AC, adenylate cyclase; PLC, phospholipase C. The 7TMD images of each subtype receptor are represented with the defined number of exons that code for the mature protein [44]; putative intron location in correspondent pre-mRNA is marked by a lightning symbol (), and alternative splicing sites are marked with stars (⋆⋆⋆).