Differences in AMPA and GABAA/B receptor subunit expression between the chronically reorganized cortex and brainstem of adult squirrel monkeys

Abstract

The primate somatosensory neuraxis provides a highly translational model system with which to investigate adult neural plasticity. Here, we report immunohistochemical staining data for AMPA and GABAA/B receptor subunits of area 3b cortex and cuneate nucleus of adult squirrel monkeys one to five years after median and ulnar nerve transection. In Area 3B cortex, the expression of GluR1 AMPAR subunits in reorganized regions are significantly increased, while the expression of GluR2/3 AMPAR subunits are not. GABAA α1 subunit expression in the reorganized region is not significantly different from control regions. Presynaptic GABABR1a subunit expression was also not significantly different between reorganized and control regions, while postsynaptic GABABR1b subunit expression was significantly decreased. In the cuneate nucleus of the brainstem, the expression of GluR1 AMPAR subunits in reorganized regions was not significantly different, while GluR2/3 AMPAR subunit expression was significantly elevated. GABAA α1 subunit expression in the reorganized region was significantly decreased. Presynaptic GABABR1a subunit expression was not significantly different, while postsynaptic GABABR1b subunit expression was significantly decreased. When subunit expression is compared, brainstem and cortical patterns diverge over longer periods of recovery. Persistent patterns of change in the cortex are stable by 1-year. Alternatively, subunit expression in the cuneate nucleus one to five years after nerve injury is similar to that seen 1-month after a reorganizing injury. This suggests that cortical plasticity continues to change over many months as receptive field reorganization occurs, while brainstem plasticity obtains a level of stable persistence by one month.