Gap junctions between perineuronal satellite cells increase in number with age in rabbit spinal ganglia.

The gap junctions between perineuronal satellite cells were studied in the spinal ganglia of 12, 42, and 79-month-old rabbits. The mean number of gap junctions per 100 microm2 of surface of the section occupied by satellite cells was significantly greater in old rabbits than young adults. Since the mean length of individual gap junctions did not change with age, the increase in number of gap junctions cannot be due to fragmentation of pre-existing gap junctions but is very likely due to the formation of new gap junctions. The increase in number of gap junctions cannot be related to an increase in number of perineuronal satellite cells since the mean number of these cells is significantly smaller in aged rabbits than in young adults. It is suggested that the increase in number of gap junctions with age may enhance the suggested neuroprotective role of satellite cells towards ganglionic neurons. The present findings, together with previous observations, suggest that the gap junctions between perineuronal satellite cells are dynamic structures, able to adapt to varying neuronal demands and varying environmental conditions.