| Summary: | 碩士 === 國防醫學院 === 生物及解剖學研究所 === 92 === 5HT-containing neurons are first detected in the raphe neurons (B4-B9 complex) at embryonic 13th day (E13) and these axons grow rapidly that fibers penetrate the frontal neocortical pole by E17. The 5-HT receptors system has been refined to include transductional and structural characteristics and to date includes 5HT1 to 5HT7 seven receptor classes, each of which may have a number of subclasses. The type 3 serotonin (5HT3) receptor, distinct from the other six classes which are all G-protein coupled receptors, is the only ligand-gated ion channel receptor for serotonin in vertebrate. Two 5HT3 receptor subunits have been cloned, subunit A (5HT3A) and B (5HT3B). 5HT3A can form functional homopentameric and with 5HT3B form heterpentameric functional receptors. 5HT3B have about 45% sequence identify with their 5HT3A homologues, but cannot form homopentameric functional receptors. The 5HT3A subunit transcripts are expressed in central and peripheral neurons in the adult rat. In contrast, 5HT3B subunit transcripts are only expressed in peripheral neurons. At the present, lack of normal 5HT receptors development has been studied. In this study, using the reverse transcriptase-polychain reaction (RT-PCR) technique studies the normal development of 5HT3 receptor subunits transcripts. The results show that both 5HT3A and 5HT3B subunits are first expressed at E11. At the end of fourth week, 5HT3B was no longer expression in the CNS. At postnatal 14th-17th days, 5HT3B transient disappeared on cortex, striatum and spinal cord but not for the brain stem and dorsal root ganglion (DRG). The current data suggest that the development of 5HT3 receptor subunits are expressed from mid-embryonic stage both in CNS and PNS. But 5HT3B stops expression at the end of fourth week postnatally in the CNS. Alternative splicing is also noted in both 5HT3A and 5HT3B subunits from mid-embryonic stage to the end of fourth week postnatally.
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