Glutamate, GABA and Serotonin concentrations in the cerebrospinal fluid and primary somatosensory cortex of birth-enucleated rats: Searching for S1 intrinsic and extrinsic epigenetic regulatory signals modulating neonatal cross-modal plasticity

Neonatal eye loss leads to an expansion of the primary somatosensory cortex (S1) in rodents. In blind rats, S1 expansion results from the predisplacement of S1 formation during the first three days of life, a process modulated by epigenetic factors. Some of these factors might be local and some others may come from extra-S1 sources such as the cerebrospinal fluid (CSF). Thus, we evaluated the concentration of glutamate, GABA and serotonin in the CSF and S1 of control and birth-enucleated rat pups. These neurotransmitters modulate through epigenetic mechanisms several aspects of brain development and also regulate S1 formation. Our results show, first, that axon segregation during barrel formation is discreetly predisplaced in birth-enucleated rats. Second, S1 glutamate, GABA and serotonin concentrations were similar in control and birth-enucleated rats during S1 formation. Lastly, CSF glutamate concentration decreased in birth-enucleated rats during S1 formation. Overall, our results open the possibility that neurochemical shifts in the CSF might modulate S1 expansion in enucleated rats. Further studies are needed to establish causal links.