Dendritic sprouting

Axonal and dendritic sprouting lead to abnormal recurrent excitatory synaptic circuits among the dentate granule cells in epileptic brain 633... 

The dendrites of neurons adjacent to those which degenerate also show extensive growth and sprouting which could facilitate abnormal and disorganised synaptic transmission and cause hyperactivity. It is also known that the dendrites of cells around an alumina focus in monkeys, as well as in human epileptic brain, lose their spinous processes, which might contribute to the paroxysmal discharge by facilitating the spread of depolarisation to the neuron soma. Certainly an increase in the number of Na+ channels on the dendrites of spinal motoneurons, which would facilitate the occurrence of reactive dendritic Na+ spikes, has been seen after axotomy. 

Estrogens stimulate sprouting of axons and dendrites in neurons in cell cultures, and there is preliminary evidence that the hormone improves memory in healthy women and in those with Alzheimer disease.285... 

FIGURE 1-22. The dendritic tree of a neuron can sprout branches, grow, and establish a multitude of new synaptic connections throughout its life. The process of making dendritic connections on an undeveloped neuron may be controlled by various growth factors, which act to promote the branching process and thus the formation of synapses on the dendritic tree. 

In humans with epilepsy, both mossy fiber sprouting, as well as decreased dendritic branching and spine density are seen (Babb and Brown, 1986 Swann et al., 2000 Wong, 2005). 

In a study of the effects of hyperthyroidism on the developing granule cell-pyramidal cell pathway (Lauder and Mugnaini, 1977, 1980) we found that thyroxine could stimulate the growth of the mossy fibers, in a dose-dependent manner, causing them to sprout collaterals which grew down into the infrapyramidal region and synapsed with the basal dendrites of pyramidal cells. Normally, the mossy fibers innervate only the apical pyramidal cell dendrites where they synapse on... 

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