Shuttle mission effects on glutamate receptor expression in the developing rodent spinal cord

Background: Within the mammalian central nervous system (CNS), glutamate receptors play a fundamental role in excitatory neurotransmission and synaptic plasticity. Studies of the neonatal cerebral cortex suggests that rearing environment can influence the dynamic patterns of glutamate receptor subunit expression during development. We examined this issue in the developing spinal cord, a well studied region of the CNS in which activity-dependent synaptic plasticity is known to occur. Methods: We compared the abundance (by immunoblot analysis) and tissue distribution (by immunohistology) of glutamate receptor subunits in neonatal animals who participated in the Neurolab Space Shuttle mission. Flight animals were either postnatal day 8 or 13 at launch and spent the next 16 d in microgravity; tissues were recovered within 12 h of landing. Littermate control animals were reared on Earth at 1 G. Results: Using semi-quantitative immunoblot assays, no statistically significant differences were found in the overall abundance of any glutamate receptor subunit in the spinal cords of the two groups of animals. Similarly, immunohistological examination of spinal cords revealed no evidence for differences in the distribution of glutamate receptor subunits between the two groups of animals. Conclusions: These results indicate that the developmental regulation of glutamate receptor subunit expression in the spinal cord is not appreciably affected by the conditions associated with this space shuttle mission and prolonged rearing period in microgravity.