Proceedings of The Physiological Society

Future Physiology (Leeds, UK) (2017) Proc Physiol Soc 39, PC06

Poster Communications

Cholinergic modulation of postnatal cell proliferation in the spinal cord

N. Altuwaijri1, S. A. Deuchars1, J. Deuchars1

1. Leeds University, Leeds, United Kingdom.

Spinal cord injury in the UK accounts for an estimated 40.000 people. Primary injury; loss of neurons and demyelination is followed by secondary injury; during which further loss of axons, neurons, and demyelination are accompanied by inflammation and cyst formation (Profyris et al., 2004). While current treatments aim at preventing the second course of injury with anti-inflammatory and anti-apoptotic strategies, a relatively new field investigates the spinal cord neurogenic niche to determine its overall neuroregenerative therapeutic potential. Many studies have elucidated the occurrence of postnatal neurogenesis in several neurogenic niches within the central nervous system. However, the microenvironment of these niches, the factors influencing their activity, and the range of their regenerative potential are yet to be investigated. The ependymal cells of the spinal cord are thought to be the neural stem/progenitor cells of this niche. Since ependymal cells respond to manipulation of nicotinic acetylcholine receptors (Corns et al., 2015); we aimed to investigate the effect of an acetylcholinesterase inhibitor on neural and glial cell proliferation and differentiation in vivo and in vitro. Adult C57BL/6 -6 week old mice (N=4 experimental group, N=4 control) received daily i.p injections of donepezil (1mg/kg) or vehicle (0.1ml saline) along with the thymidine analogue EdU (10mM) for 7 days. Spinal cord sections were treated for EdU detection then immunohistochemically analysed for astrocytic and oligodendrocytic differentiation using S100β and PanQkI respectively. In the central canal of donepezil treated animals (mean 2.56 ± SEM 0.311, N=4 animals, n=88 sections) there were significantly lower (P=0.002) numbers of EdU positive cells compared to control (mean 3.95 ± 0.36, N=4 animals, n= 75 sections). The positive control to this experiment was the hippocampus of each animal. The cholinergic modulatory effect of donepezil on the hippocampus was clearly discernable; significantly increasing proliferation in the dentate gyrus (P=0.0054). The differentiation of EdU positive cells into astrocytes but not oligodendrocytes was modulated by donepezil. The effects of donepezil were tested in vitro by the addition of (5µM) of donepezil and (1µM) EdU to in vitro spinal cord slices and compared to a control group. The numbers of EdU positive cells around the central canal in donepezil treated slices were significantly lower (P=0.002, mean 3.95 ± 0.38 SEM, N=3, n=23) in comparison to control (mean 5.05 ± 1.57 SEM, N=3, n=17). Slices treated with cytisine (20 µM; a partial nicotinic acetylcholine receptor agonist had significantly lower (P=0.016, mean 1.1875 ± 0.22 SEM, N=3, n=16) numbers of EdU positive cells in the central canal compared to those in control. Thus the identity and role of each receptor subtype is yet to be tested in the spinal cord.

Where applicable, experiments conform with Society ethical requirements