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Tripathi, P.P.* ; di Giovannantonio, L.G.* ; Viegi, A.* ; Wurst, W. ; Simeone, A.* ; Bozzi, Y.*

Serotonin hyperinnervation abolishes seizure susceptibility in Otx2 conditional mutant mice.

J. Neurosci. 28, 9271-9276 (2008)
DOI
Open Access Green as soon as Postprint is submitted to ZB.
The homeobox-containing transcription factor Otx2 is crucially involved in fate determination of midbrain neurons. Mutant mice, in which Otx2 was conditionally inactivated by a Cre recombinase expressed under the transcriptional control of the Engrailed1 (En1) gene (En1(cre/+); Otx2(flox/flox)), show a reduced number of dopaminergic neurons and an increased number of serotonergic neurons in the ventral midbrain. Despite these developmental anatomical alterations, En1(cre/+); Otx2(flox/flox) adult mice display normal motor function. Here, we further investigated the neurological consequences of Otx2 inactivation in adult En1(cre/+); Otx2(flox/flox) mice. Adult En1(cre/+); Otx2(flox/flox) mice showed increased serotonin (5-HT) levels in the pons, ventral midbrain, hippocampus (CA3 subfield), and cerebral cortex, as indicated by HPLC and immunohistochemistry. Conversely, SERT (5-HT transporter) levels were decreased in conditional mutant brains. As a consequence of this increased 5-HT hyperinnervation, En1(cre/+); Otx2(flox/flox) mice were resistant to generalized seizures induced by the glutamate agonist kainic acid (KA). Indeed, prolonged pretreatment of En1(cre/+); Otx2(flox/flox) mice with the 5- HT synthesis inhibitor para- chlorophenylalanine (pCPA) restored brain 5-HT content to control levels, fully reestablishing KA seizure susceptibility. Accordingly, c- fos mRNA induction after KA was restricted to the hippocampus in En1(Cre/+); Otx2(flox/flox) mice, whereas a widespread c- fos mRNA labeling was observed throughout the brain of En1(Cre/+); Otx2(flox/flox) mice pretreated with pCPA. These results clearly show that increased brain 5- HT levels are responsible for seizure resistance in En1(cre/+); Otx2(flox/flox) mice and confirm the important role of 5-HT in the control of seizure spread.
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Publication type Article: Journal article
Document type Scientific Article
Keywords serotonin transporter; pCPA; kainic acid; hippocampus; seizures; epilepsy
ISSN (print) / ISBN 0270-6474
e-ISSN 1529-2401
Journal Journal of Neuroscience
Quellenangaben Volume: 28, Issue: 37, Pages: 9271-9276 Article Number: , Supplement: ,
Publisher Society for Neuroscience
Reviewing status Peer reviewed
Institute(s) Institute of Developmental Genetics (IDG)