The data on the responses of inhibitory circuits to the spinal cord transection are conflicting. We examined the segmental distribution of determinants of GABAergic and glycinergic transmission in adult rats five weeks after complete spinal cord transection at Th9-10. Concentrations of the GABA and glycine (Gly) in segments below the lesion were evaluated in rats that did not receive any treatment. Decreases in GABA (24%) and Gly (26%) were found only in the lumbar L1-2 segments. Two other groups of spinal rats received microinjections of PBS (SP-PBS) or AAV- EGFP transgene (SPEGFP) to L1-2. Both led to GABA decrease (43% in L1-2 and 23% in L3-6 segments) and a decrease in mRNA for GAD67 (43% in L1-2 in both groups and 10% in L3-6 segment of SP-PBS vs 49% in L3-6 of SP-EGFP rats). The respective decreases in mRNA for Gly transporter GlyT2 were 68 vs. 72% in L1-2 and 29 vs. 76% in L3-6 segments. These changes were not accompanied by changes in the density of GABAergic/glycinergic network and inputs to motoneurons identified with GAD67/GlyT2 immunostaining. We conclude that albeit spinalization does not reduce inhibitory inputs to lumbar motoneurons it leads to long-term impairment in presynaptic determinants of inhibitory neurotransmission which may attenuate inhibitory signaling. Support: NN401 324739 grant.
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