Slc6a4, Tph2, Htr1b, Htr2a genes expression in the mouse spinal cord after microgravity exposure simulation on earth

Aim. To determine the level of gene expression of the serotonergic neurotransmission system (Slc6a4, Tph2, Htr1b, Htr2a) in the cervical and lumbar enlargement of the spinal cord for mice after 30-day microgravity exposure simulation by using the antiorthostatic unloading model by Morey-Holton et al. and a subsequent 7-dayrecovery period. Methods. The experimental animals were divided into three groups: Unloading group with mice undergoes hindlimb-unloading procedure for 30 days (n=5); Recovery group with mice undergoes hindlimb-unloading procedure for 30 days, followed by readaptation within 7 days (n=5); Control group with mice kept at standard vivarium conditions (n=5). The expression level of genes encoding synaptic proteins in the central nervous system was estimated by a real-time polymerase chain reaction. Results. There were no statistically significant differences between the studied groups regarding the Tph2, Htr1b, and Htr2a expressions in the cervical and lumbar enlargement of the spinal cord. Compared to the Control group, a statistically significant increase (6.3 times) in the level of Slc6a4 expression in the lumbar spinal cord was revealed after microgravity exposure simulation (Unloading group), followed by a 3-fold decrease during the readaptation period (Recovery group ). Conclusion. The expression level of the Slc6a4 gene, which encodes carrier protein involved in the function of serotonergic synapses, may indicate the potential involvement of this neurotransmitter system in the pathogenesis of movement disorders after microgravity exposure simulation on earth.