Comparing the Expression of Genes Related to Serotonin (5-HT) in C57BL/6J Mice and Humans Based on Data Available at the Allen Mouse Brain Atlas and Allen Human Brain Atlas

Figure 1

Representation of serotonergic synapses (synthesis, storage, liberation, and recapture). Processes related to serotonergic synapses. (a) Synthesis and metabolism: tryptophan is taken by the neuron through active transport mechanisms; (b) storage: once synthesized, it is stored in synaptic vesicles by vesicular transporters of monoamines (Vmat). When it is liberated, the serotonin interacts with various types of receptors; (c) postsynaptic receptors: the vast majority of postsynaptic receptors are G-protein coupled metabotropic receptors (HTR1A and HTR1B coupled to protein Gi and receptors HTR4, HTR6, and HTR7 are coupled to protein Gs) that activate adenylyl cyclase (AC), which in turn activates cyclic AMP, generating a cellular response; HTR2A and HTR2C are coupled to protein Gq and when activated, activate phospholipase C that triggers activity in inositol trisphosphate (IP₃), diglyceride (DAG), and an increase in levels of intracellular calcium (Ca⁺⁺), leading to a cellular response. The HTR3 receptors are postsynaptic and ionotropic, activated by ligands, allowing the flow of sodium (Na⁺) ions; (d) inactivation: once recaptured, the serotonin is inactivated by monoamine oxidase (MAO) enzymes, generating 5-hydroxyindoleacetic acid (5-HIAA); (e) presynaptic stimulation: HTR1B and HTR1D receptors modulate the liberation of serotonin. Adapted from [12].