Seizure-induced formation of basal dendrites on granule cells of the rodent dentate gyrus

Excerpt

Status epilepticus results in several neuroplastic changes to the granule cells of the hippocampal dentate gyrus. These include mossy fiber sprouting, granule cell dispersion, hilar ectopic granule cells and hilar basal dendrites. This chapter reviews the seizure-induced formation of hilar basal dendrites on granule cells in rodents. This aberrant structural change is associated with a new, predominantly excitatory input to granule cells and more excitatory interconnections between granule cells – i.e., a new pathway in addition to that arising from sprouted mossy fibers in the inner molecular layer. Hilar basal dendrites are found on newly generated dentate granule cells; significant increases in the frequency of newly generated granule cells with hilar basal dendrites are found within one day after seizures are induced. The development of hilar basal dendrites on granule cells occurs rapidly after seizures; their persistence may be due to the rapidly forming synapses that integrate these newly-generated granule cells into synaptic circuitry. The basal dendrites appear to use hypertrophied astrocytic processes as guides for growth into the hilus. These data provide insight into anatomical and functional plasticity of rodent granule cells following seizures. The role that these basal dendrites play in the development of spontaneous seizures has yet to be determined.