Factors that influence the expression of neurotransmitter-gated ion channels on developing peripheral neurons

Synapse formation involves multiple coordinated events between the presynaptic and the postsynaptic nerve that ultimately results in the expression of the appropriate neurotransmitters at the presynaptic nerve terminal and the matching neurotransmitter receptors on the opposing postsynaptic membrane. For my thesis research, I investigate different aspects of neurotransmitter receptor gene expression, an early step in the process of synaptogenesis. Specifically, I focus on two different neurotransmitter-gated ion channels that are expressed on neonatal rat peripheral neurons: the serotonin 5-HT₃ receptor (5-HT₃R) and the neuronal nicotinic acetylcholine receptor (nAChR).; The 5-HT₃R is expressed on both nodose sensory neurons and sympathetic neurons. However, little is known about 5-HT₃R expression during neonatal development or about the factors that regulate its expression. To investigate 5-HT₃R gene expression, first I examined 5-HT ₃R mRNA levels in nodose and sympathetic neurons as they develop in vivo and in culture. My results show that 5-HT ₃R gene expression is differentially regulated in these two populations of neurons. In addition, I demonstrate that 5-HT₃R gene expression in nodose neurons depends on target innervation and can be modulated by neurotrophins.; Neonatal sympathetic neurons express five different neuronal nAChR subunit genes. One unresolved issue is the contribution of these five subunits to nAChR function. To investigate this issue, I altered the expression of one nAChR subunit gene, α3, using transient transfection procedures. To do this, first I modified and optimized gene transfer procedures for sympathetic neurons, based on recombinant adenovirus vectors. sing this approach, I overexpressed sense and antisense α3 mRNA and investigated how the changes in α3 subunit expression affect ACh-evoked currents on cultured sympathetic neurons. I show that changes in α3 mRNA levels alter the magnitude of ACh-evoked current densities. My results indicate that α3 gene expression is rate-limiting for the assembly and insertion of nAChRs on sympathetic neurons.; Together, my results show that multiple mechanisms influence the expression neurotransmitter-gated ion channel genes on peripheral neurons.