Decortication Study
Objective: To determine the role of cortical input in mediating 3-nitropropionic acid (3-NP)-induced striatal lesions by comparing lesion formation in decorticated versus intact animals
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Protocol Steps
Prior decortication surgery
Perform decortication procedure prior to 3-NP administration to remove cortical input
Note: This is the key manipulation to test cortical involvement in 3-NP-induced lesions
View evidence from paper
“The lesions produced by intrastriatal injection or systemic administration of 3-NP were blocked by prior decortication”
Intrastriatal 3-NP injection
Administer 3-NP directly into the striatum at varying doses to produce dose-dependent lesions
Note: Produces dose-dependent striatal lesions affecting both spiny projection neurons and aspiny interneurons
View evidence from paper
“Following intrastriatal injection 3-NP produced dose-dependent striatal lesions”
Subacute systemic 3-NP administration
Administer 3-NP systemically via subacute dosing regimen
Note: Produces age-dependent bilateral striatal lesions with sparing of dopaminergic afferent projections
View evidence from paper
“Subacute systemic administration of 3-NP produced age-dependent bilateral striatal lesions with a similar neurochemical profile”
Chronic systemic 3-NP administration
Administer 3-NP systemically over extended duration
Note: Produces lesions confined to striatum with relative sparing of NADPH-diaphorase interneurons and growth-related proliferative changes in dendrites
View evidence from paper
“chronic (1 month) administration produced lesions confined to the striatum in which there was relative sparing of NADPH-diaphorase interneurons”
MK-801 antagonist testing
Administer NMDA antagonist MK-801 to test whether NMDA receptors mediate 3-NP effects
Note: MK-801 did not block intrastriatal 3-NP effects, suggesting non-NMDA excitotoxic mechanism
View evidence from paper
“the NMDA antagonist MK-801 did not block the effects of intrastriatal 3-NP, consistent with a non-NMDA excitotoxic mechanism”
Freeze-clamp energy metabolism measurement
Measure energy metabolism in striatum using freeze-clamp technique
Note: Demonstrates that 3-NP impairs energy metabolism in vivo
View evidence from paper
“Both freeze-clamp measurements and chemical shift magnetic resonance spectroscopy showed that 3-NP impairs energy metabolism in the striatum in vivo”
Magnetic resonance spectroscopy measurement
Measure energy metabolism using chemical shift magnetic resonance spectroscopy
Note: Confirms energy metabolism impairment in striatum
View evidence from paper
“Both freeze-clamp measurements and chemical shift magnetic resonance spectroscopy showed that 3-NP impairs energy metabolism in the striatum in vivo”
Microdialysis glutamate measurement
Measure extracellular glutamate concentrations using microdialysis
Note: Shows no increase in extracellular glutamate after systemic 3-NP administration
View evidence from paper
“Microdialysis showed no increase in extracellular glutamate concentrations after systemic administration of 3-NP”
Neurochemical evaluation
Assess markers of spiny projection neurons (GABA, substance P, calbindin) and aspiny interneurons (somatostatin, neuropeptide Y, NADPH-diaphorase)
Note: Both neuron types equally affected by intrastriatal injection; chronic systemic administration shows relative sparing of NADPH-diaphorase interneurons
View evidence from paper
“Neurochemical and histologic evaluation showed that markers of both spiny projection neurons (GABA, substance P, calbindin) and aspiny interneurons (somatostatin, neuropeptide Y, NADPH-diaphorase) were equally affected”
Histologic evaluation
Perform histologic examination of striatal lesions and neuronal changes
Note: Chronic administration shows growth-related proliferative changes in dendrites similar to Huntington's disease
View evidence from paper
“Chronic administration of 3-NP over 1 month produces selective striatal lesions that replicate many of the characteristic histologic and neurochemical features of HD”