Pain & Central Nervous System Week via NewsEdge :

2008 SEP 8 - (NewsRx.com) -- According to recent research from the United States, "In patients with temporal lobe epilepsy some dentate granule cells develop basal dendrites (see also Epilepsy). The extent of excitatory synaptic input to basal dendrites is unclear, nor is it known whether basal dendrites receive inhibitory synapses."

"We used biocytin to intracellularly label individual granule cells with basal dendrites in epileptic pilocarpine-treated rats. An average basal dendrite had 3.9 branches, was 612 mu m long, and accounted for 16% of a cell's total dendritic length. In vivo intracellular labeling and postembedding GABA-immunocytochemistry were used to evaluate synapses with basal dendrites reconstructed from serial electron micrographs. An average of 7% of 1,802 putative synapses were formed by GABA-positive axon terminals, indicating synaptogenesis by interneurons. Ninety-three percent of the identified synapses were GABA-negative. Most GABA-negative synapses were with spines, but at least 10% were with dendritic shafts. Multiplying basal dendrite length/cell and synapse density yielded an estimate of 180 inhibitory and 2,140 excitatory synapses per granule cell basal dendrite. Based on previous estimates of synaptic input to granule cells in control rats, these findings suggest an average basal dendrite receives approximate to 14% of the total inhibitory and 19% of excitatory synapses of a cell," wrote K.K. Thind and colleagues, Stanford University.

The researchers concluded: "These findings reveal that basal dendrites are a novel source of inhibitory input, but they primarily receive excitatory synapses."

Thind and colleagues published their study in the Journal of Comparative Neurology (Synaptic input to dentate granule cell basal dendrites in a rat model of temporal lobe epilepsy. Journal of Comparative Neurology, 2008;509(2):190-202).

For additional information, contact P.S. Buckmaster, Stanford University, Dept. of Comparative Medical, 300 Pasteur Dr., R321 Edwards Bldg, Stanford, CA 94305, USA.

Publisher contact information for the Journal of Comparative Neurology is: Wiley-Liss, Division John Wiley & Sons Inc., 111 River St., Hoboken, NJ 07030, USA.

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