کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6273583 | 1614799 | 2014 | 11 صفحه PDF | دانلود رایگان |
- The kinetic of Clâ transport was quantified in rat and human neocortical neurons.
- The KCC2 blocker VU0240551 decreased of Clâ transport in rat and human neurons.
- In about two-thirds of human neurons KCC2 are reduced by about 70% vs. the others.
- The transport rate by the anion exchanger was indistinguishable in rat and human neurons.
The normal function of GABAA receptor-mediated inhibition is governed by several factors, including release of GABA, subunit composition and density of the receptors and in particular by the appropriate ionic gradient. In the human epileptogenic neocortex an impaired chloride (Clâ) gradient has been proposed, due to decreases of potassium-coupled chloride transport (KCC2) and voltage-gated Clâ channels (ClC). Regarding sodium- and potassium-coupled Clâ transport (NKCC1) both up- and downregulations have been proposed.We investigated changes of Clâ homeostasis of human and rat neocortical neurons (layer 2/3) with intracellular recordings and iontophoretic Clâ loading employing selective compounds. After cessation of iontophoresis, the IPSPA amplitudes of rat neurons recovered with a time constant (Ïrec) of 6.5 s (n = 21). In human neurons, Ïrec averaged 17.8 s (n = 36; 23 resections). Application of the novel KCC2 blocker VU0240551 (1 μM) caused in rat neurons a reversible prolongation of Ïrec from 5.7 to 8.1 s (n = 11), corresponding to a VU0240551-sensitive Clâ transport rate (1/ÎÏrec) of 0.0504 sâ1. In human neurons, Ïrec increased on application of 1 μM VU0240551, on average from 15.1 to 20.3 s (n = 17). The human neurons comprised two subgroups with different Ïrec when segregated according to a border given by the mean + 2 s.d. of rat neurons. In one group, Ïrec averaged 8.7 s (n = 6) and reversibly increased to 14.6 s in the presence of 1 μM VU0240551, corresponding to a Clâ transport rate of 0.0504 sâ1. The other group had an average Ïrec of 18.5 s which increased in the presence of 1 μM VU0240551 to 23.3 s (n = 11), indicating a much smaller rate (0.0151 sâ1). Addition of DIDS, a presumed blocker of anion exchanger (AE), increased the Ïrec of rat neurons from 7.5 to 8.8 s (n = 6) corresponding to a DIDS-sensitive rate of 0.0185 sâ1. In human neurons, DIDS increased Ïrec from 23.3 to 50.7 s (n = 7), corresponding to a DIDS-sensitive rate of 0.0200 sâ1.These data suggest a greatly reduced KCC2-mediated transport rate in most of the human neurons. The two subgroups observed in human tissue indicate a considerable variability of Clâ transport within a given tissue from almost normal to greatly impeded, predominated by a decline of KCC2 whereas AE is unaltered.
Journal: Neuroscience - Volume 277, 26 September 2014, Pages 831-841