Serotonin (5-HT) neurons are currently of research interest since these neurons have a crucial role in regulating human homeostasis and psychological states. These neurons are generated from the hindbrain raphe nuclei and are classified into rostral (r1-r3) and caudal (r5-r8) groups. While rostral groups have been successfully developed, only a few functional caudal 5-HT neurons are available i…