Dye-coupling in human neocortical tissue resected from children with intractable epilepsy

Interneuronal communication mediated by gap junctions has been proposed to have an important role in brain development and in the genesis of epilepsy. Indirect evidence for the existence and function of gap junctions has been obtained by studying dye-coupling, the transfer of the low-molecular-weight fluorescent dye Lucifer yellow (LY), among neurons. In the present study, the incidence of dye-coupling was assessed at different stages of human postnatal brain development. Pathological neocortical tissue was obtained from children from 3 to 172 months of age suffering from pediatric epilepsy and undergoing surgery to alleviate intractable seizures. Tissue samples were classified into least and most abnormal according to a number of diagnostic measures to ascertain if the incidence of dye-coupling could be related to the degree of epileptogenicity of the sample. Regardless of the degree of abnormality, a significant developmental decrease in the incidence of dye-coupling was observed. In children 3-16 months, dye-coupling occurred in 38% of single intracellular injections of LY. From 32 to 83 months, the frequency of dye-coupling decreased to 13%. Finally, from 93 to 172 months, dye-coupling was observed in only 4% of injections. The frequency of dye-coupling between the least and most abnormal samples was not significantly different, although the frequency of dye-coupling was higher in the least abnormal samples from the youngest group (3-16 months). These findings underscore the role of gap junctions during brain development. However, they do not provide support, at least in vitro, for the hypothesis that gap junctions have an important role underlying epilepsy.