| 16725129 |
Skov J, Andreasen M, Nedergaard S: Postnatal development of a new type of epileptiform activity in the rat hippocampus. Brain Res. 2006 Jun 22;1096(1):61-9. Epub 2006 May 24.
Long-term application of Cs (+) (5 mM) induces an epileptiform field potential (Cs-FP) in area CA1 of the rat hippocampus, which is independent of N-methyl-D-aspartate (NMDA) and non-NMDA glutamate receptors and gamma-aminobutyric acid (GABA)(A) receptors. To gain insight into possible mechanisms for the induction of the Cs-FP, we investigated the postnatal development of the response. In brain slices prepared from rats at different ages, the Cs-FP was evoked by stimulation of the Schaffer-collateral-commisural pathway. We found that expression of this potential was clearly dependent on the postnatal age. Thus, the Cs-FP was completely absent at 1 week of age. By 2 weeks, a reduced form of the response was observed, whereas slices taken from 3-week-old rats, displayed full Cs-FP, which were indistinguishable in size and shape from the adult form. In the presence of 4-aminopyridine, potentials resembling the Cs-FP were evoked. These potentials showed a similar age-dependency as the Cs-FP. The Na (+)/K (+) pump inhibitor dihydroouabain (DHO), when present during wash-in of Cs (+), gave a partial block of the Cs-FP in adult slices. This effect was not seen when DHO was applied after development of the Cs-FP. The data indicate that the processes necessary for expression of the Cs-PF are absent at birth and develop during the second postnatal week. We propose that the Cs-FP depends on Cs (+) entry into presynaptic neurons, and that the Na (+)/K (+) pump contributes to this transport of Cs (+). The observed age-dependency could therefore, in part, reflect the delayed development of the Na (+)/K (+) pump. |
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