Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCB261

Poster Communications

GABAergic modulation of cells within the
neurogenic niche of the postnatal spinal cord

N. Shafin1, J. Deuchars1, A. Wilson2, J. Chuquet3, S. Deuchars1

1. School of Biomedical Sciences, University of Leeds, Leeds, West Yorkshire, United Kingdom. 2. School of Chemistry, University of Leeds, Leeds, United Kingdom. 3. INSERM Lab, University of ROUEN, ROUEN, France.

Modulation of GABA mediated inhibition is one of the most important approaches for the treatment of CNS diseases. Precise targeting of such treatments depends on identification and characterisation of the different subunit complexes that exist. In the CNS, there are pools of neural stem cells (NSC), which can differentiate to become neurones, astrocytes or oligodendrocytes while progenitor cells have limited lineage. In addition to brain regions, where NSCs are now known to exist, the spinal cord area also has a neurogenic potential in the form of ependymal cells (ECs)1. Ependymal cells (ECs) around the central canal of the spinal cord respond to GABA2. One approach to develop pharmacological treatments to modulate stem cell activity is to determine how endogenous proteins and receptors on NSCs can regulate their behaviour. Responses to GABA were determined and compounds known to modulate GABA receptors at selective sites were tested using both bath and puff applications. Prolonged application of FGIN-1-27; 1 μM (peripheral benzodiazepine (BZD) receptor (TSPO) agonist) significantly enhanced (P<0.05) responses to GABA in ECs. This may be due to the neurosteroidogenic effect of TSPO activation. Bath applications of octadecaneuropeptide (ODN), the endogenous ligand of the central BZD receptor alone caused both depolarising and hyperpolarising effects on ECs but did not significantly affect responses to GABA. Local ODN application caused fast hyperpolarisations that were mimicked by local application of low (1.25-2.5 μM) concentrations of GABA. To further characterise the GABA receptor mediated responses, agonists and antagonists were used to enhance and block the receptor accordingly. Since TPMPA antagonised responses to ODN (P<0.05) and reduced the responses to low concentrations of GABA, this suggests that GABA receptors contain subunits from both GABAA and GABAC. Baclofen; 1 μM & 5 µM (a selective GABAB receptor agonist) also hyperpolarised ECs, an effect antagonised by CGP 55845 (GABAB antagonist), indicating a further role for GABAB receptors. To examine whether baclofen could affect the level of proliferation in acute spinal cord slices, the thymidine analogue 5-Ethynyl-2'-deoxyuridine (EdU) was added to the slices in the presence or absence of baclofen. The numbers of EdU-positive cells were significantly lower in baclofen treated slices (P<0.05) compared with control EdU-positive cells in central canal area. If cells within the central canal area respond to GABA, it is possible that following an injury or onset of pathological condition, GABA could be released in this area to modulate proliferation and differentiation. These experiments will help to confirm the role of GABA receptors in spinal cord cell proliferation.

Where applicable, experiments conform with Society ethical requirements