Ms. Levine et al., Enhanced sensitivity to N-methyl-D-aspartate receptor activation in transgenic and knockin mouse models of Huntington's disease, J NEUROSC R, 58(4), 1999, pp. 515-532
We used two mouse models of Huntington's disease (HD) to examine changes in
glutamate receptor sensitivity and striatal electrophysiology. One model,
a transgenic, consisted of mice expressing exon 1 of the human HD gene and
carrying 141-157 CAG repeat sequences (R6/2 line). The second model, a CAG
repeat "knockin," consisted of mice with different lengths of CAG repeats (
CAG71 and CAG94 repeats). The effects of glutamate receptor activation were
examined by visualizing neurons in brain slices with infrared videomicrosc
opy and differential interference contrast optics to determine changes in s
omatic area (cell swelling). Striatal and cortical neurons in both models (
R6/2 and CAG94) displayed more rapid and increased swelling to N-methyl-D-a
spartate (NMDA) than those in controls, This effect was specific as there w
ere no consistent group differences after exposure to alpha-amino-3-hydroxy
-5-methyl-4-isoxazole propionic acid (AMPA) or kainate (KA). Intracellular
recordings revealed that resting membrane potentials (RMPs) in the R6/2 tra
nsgenics were significantly more depolarized than those in their respective
controls. RMPs in CAG94 mice also were more depolarized than those in CAG7
1 mice or their controls in a subset of striatal neurons. Confirming previo
us results, R6/2 mice expressed behavioral abnormalities and nuclear inclus
ions. However, CAG71 and CAG94 knockins did not, suggesting that increased
sensitivity to NMDA may occur early in the disease process. These findings
imply that NMDA antagonists or compounds that alter sensitivity of NMDA rec
eptors may be useful in the treatment of HD, J. Neurosci. Res. 58:515-532,
1999. (C) 1999 Wiley-Liss, Inc.