Transient and progressive electrophysiological alterations in the corticostriatal pathway in a mouse model of Huntington's disease.
Alterations in the corticostriatal pathway may precede symptomatology and striatal cell death in Huntington's disease (HD) patients. Here we examined spontaneous EPSCs in striatal medium-sized spiny neurons in slices from a mouse model of HD (R6/2). Spontaneous EPSC frequency was similar in young (3-4 weeks) transgenics and controls but decreased significantly in transgenics when overt behavioral symptoms began (5-7 weeks) and was most pronounced in severely impaired transgenics (11-15 weeks). These differences were maintained after bicuculline or tetrodotoxin, indicating they were specific to glutamatergic input and likely presynaptic in origin. Decreases in presynaptic and postsynaptic protein markers, synaptophysin and postsynaptic density-95, occurred in 11-15 week R6/2 mice, supporting the electrophysiological results. Furthermore, isolated, large-amplitude synaptic events (>100 pA) occurred more frequently in transgenic animals, particularly at 5-7 weeks, suggesting additional dysregulation of cortical inputs. Large events were blocked by tetrodotoxin, indicating a possible cortical origin. Addition of bicuculline and 4-aminopyridine facilitated the occurrence of large events. Riluzole, a compound that decreases glutamate release, reduced these events. Together, these observations indicate that both progressive and transient alterations occur along the corticostriatal pathway in experimental HD. These alterations are likely to contribute to the selective vulnerability of striatal medium-sized spiny neurons.
Cepeda
Carlos
C
Mental Retardation Research Center, University of California at Los Angeles, Los Angeles, California 90095, USA.
Hurst
Raymond S
RS
Calvert
Christopher R
CR
Hernández-Echeagaray
Elizabeth
E
Nguyen
Oanh K
OK
Jocoy
Emily
E
Christian
Lindsey J
LJ
Ariano
Marjorie A
MA
Levine
Michael S
MS
D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects / Q000503:physiopathology*; D003342:Corpus Striatum / Q000187:drug effects / Q000503:physiopathology*; D004195:Disease Models, Animal; D018450:Disease Progression; D004594:Electrophysiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D018756:GABA Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism; D006816:Huntington Disease / Q000503:physiopathology*; D066298:In Vitro Techniques; D051379:Mice; D009434:Neural Pathways / Q000187:drug effects / Q000503:physiopathology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D019782:Riluzole / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D018696:Neuroprotective Agents; D026902:Potassium Channel Blockers; D018698:Glutamic Acid; D013779:Tetrodotoxin; D019782:Riluzole