Densities of glutamatergic and GABAergic presynaptic terminals are altered in experimental cortical dysplasia.
OBJECTIVE
Cortical dysplasia (CD) is a major cause of epilepsy in children and adults, but underlying mechanisms of epileptogenesis in this disorder are poorly understood. We have utilized the irradiated rat model to study an injury-based form of diffuse CD in rats. Prior studies in this model have shown reduced numbers of γ-aminobutyric acid (GABA)ergic interneurons and reduced inhibitory synaptic currents in pyramidal cells in CD. We analyzed the number of excitatory and inhibitory presynaptic terminals in the neocortex of irradiated rats to better characterize altered connectivity in experimental CD.


METHODS
Antibodies to vesicular glutamate transporter 1 (VGLUT1), vesicular glutamate transporter 2 (VGLUT2), vesicular GABA transporter (VGAT), and parvalbumin (PV) were used to quantify glutamatergic and GABAergic presynaptic terminals in control and dysplastic cortex.


RESULTS
We found that the density of VGLUT1 terminals was increased in CD in comparison to layers IV, V, and VI in control cortex. VGLUT2 terminals were increased in CD compared to layers IV and VI. VGAT terminals were reduced in CD compared to layers II/III, IV, and V in controls as were PV-immunoreactive somata and terminals.


CONCLUSIONS
These findings suggest an overall increase in excitatory synaptic connectivity and decrease in inhibitory synaptic connectivity in CD in irradiated rat. We propose that these changes contribute to hyperexcitability in these animals and may contribute to epileptogenicity in some forms of human CD.
Zhou
Fu-Wen
FW
Department of Neurosurgery and the McKnight Brain Institute, University of Florida, Gainesville, Florida, USA.
Roper
Steven N
SN
D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D002540:Cerebral Cortex / Q000196:embryology / Q000254:growth & development / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D004622:Embryo, Mammalian; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism*; D017619:Hemibody Irradiation / Q000009:adverse effects; D008297:Male; D054220:Malformations of Cortical Development / Q000209:etiology / Q000473:pathology*; D010320:Parvalbumins / Q000378:metabolism; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000503:physiopathology; D017729:Presynaptic Terminals / Q000378:metabolism*; D051381:Rats; D050599:Vesicular Glutamate Transport Protein 2 / Q000378:metabolism; D050496:Vesicular Glutamate Transport Proteins / Q000378:metabolism; D050495:Vesicular Inhibitory Amino Acid Transport Proteins / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D010320:Parvalbumins; C493475:Slc17a6 protein, rat; C118623:Slc32a1 protein, rat; D050599:Vesicular Glutamate Transport Protein 2; D050496:Vesicular Glutamate Transport Proteins; D050495:Vesicular Inhibitory Amino Acid Transport Proteins; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid