Activity-dependent expression of GAD(67) in the granule cells of the rat hippocampus

Citation
M. Ramirez et R. Gutierrez, Activity-dependent expression of GAD(67) in the granule cells of the rat hippocampus, BRAIN RES, 917(2), 2001, pp. 139-146
Citations number
25
Categorie Soggetti
Neurosciences & Behavoir
Journal title
BRAIN RESEARCH
ISSN journal
00068993 → ACNP
Volume
917
Issue
2
Year of publication
2001
Pages
139 - 146
Database
ISI
SICI code
0006-8993(20011102)917:2<139:AEOGIT>2.0.ZU;2-M
Abstract
In the normal granule cells of the dentate gyrus glutamate, GABA and glutam ic acid decarboxylase (GAD(67)) coexist. After kindled seizures, this enzym e is transiently overexpressed and simultaneous glutamatergic and GABAergic transmission in the mossy fiber projection occurs. Since this dual transmi ssion is also seen after acutely-induced seizures, we decided to study the relationship between the expression of GAD(67) and the induction of simulta neous glutamatergic and GABAergie transmission by kindled or acutely induce d seizures. We also explored whether kindling of the dentate gyrus in vitro , that does not induce epileptiform activity, could induce the expression o f GAD(67). We confirm that kindling epilepsy induces the expression of GAD( 67) in the dentate gyrus. Despite the emergence of GABAergic transmission i n the mossy fiber projection after a single seizure, GAD(67) expression in the dentate gyrus appeared similar to controls, however, in the mossy fiber s an enhanced immunostaining was evident. Interestingly, kindling the denta te gyrus in vitro induces a marked GAD(67) staining in the granule cells. O ur results show that after the activity-dependent emergence of simultaneous glutamatergic and GABAergic transmission from the mossy fibers, GAD(67) is expressed in the mossy fibers and, upon long-lasting enduring stimulation periods, also in the dentate gyrus. Thus, this phenomenon does not depend o n the presence of epileptic activity, but rather, on increased excitatory i nput onto the dentate gyrus, This can represent a protective mechanism that can sustain GABA synthesis in an activity-dependent manner. (C) 2001 Elsev ier Science B.V. All rights reserved.