Modificazioni delle giunzioni gap fra le cellule satelliti dei gangli spinali di topo nel corso dell'invecchiamento

Glial cells in both central and peripheral nervous systems are connected by gap junctions, which allow electrical and metabolic coupling between them. This study investigated coupling between satellite glial cells that envelope the spinal ganglion neurons in mice aging from 90 to 730 days using the dye coupling technique and electron microscopy. Experiments were done on spinal ganglia L4 and L5. Both the dye coupling technique and the electron microscopy showed that clusters of two-six neurons sharing a common satellite cell sheath were present in mice of all ages. Dye coupling incidence between satellite cells associated with a single neuron increased from 24.2% at 90 days to 50.5% at 730 days. Dye coupling incidence between satellite cells that are in contact with two or more neurons increased from 2.7% at 90 days to 18.6% at 730 days. Examination of the ganglia by the electron microscope showed that the density of gap junctions (number of gap junctions per 100 µm2 of surface area of satellite cells) was about seven fold greater in 730 days than in 90 days both in satellite cells associated with a single neuron and in satellite cells that are in contact with two or more neurons. The mean length of individual gap junction did not change with age. These results provide strong evidence for an increase of functional coupling between satellite cells during life. This increase is apparently due to an increase in the total area of the system of gap junctions connecting these cells.