| Abstract: | ![]()
Adult central neurons exhibit significant structural and moledular chnges in epilepsy. We have examined changesin two markers of morphological and physiological plasticuity, Tα1 α-tubkulin (Tα1) and neuropeptide Y (NPY) mRNAs, inresponse tointermittent (20 Hz, 10 seconds), 1 stimulation of therat perforant path in vivo. Stimulus trins elicited brief (0.5–3 seconds) afterdischarges intheipsilateral dentate gyrus (DG). Four hours of stimulation caused no significant loss ofinhibitiobn intthe DG 40–48 hours after stimulationceased. Hiowever, it did lead to an increase in NPY mRNA in neurons of the ipsilateral and to a lesser extent, contralateral DGs and Ammon's Horn. Many of these were presumably interneurons tht normally express NPY. However, dentate granule cells (DGCs), which do not normally express this peptide, also expressed robust levels of NPY mRNA bilaterally. NPY mRNA levels peaked at 4–24 hours and returned to baseline by 48 hours poststimulation. Although 24 hourz of stimulation induced a similar increse in interneurons, DGCs showed no detecstable NPY mRNA. Afterdischarges were necessaryto elevate NPY mRNA exprssion. Four hours of stimulation evelvated Tα1 mRNA expsression in both ipsilateral and, to a lesser extent, contralteral DGCs; this elevation peaked at 24 hours poststimulation and declined to baseline by 72 hours. Stimulation for 24 hors caused broader changes in Tα1 mRNA expression, with incrases in DGCs and in CA3 pyramidal cells bilterally. Acute denervattion of the DG did not affect Tα1 mRNA level in the hippocampal formation. Elevated sysnaptic input resulting in afterdischarges, but not necessarily in excitbility changes in the DG, led to altrations in the exspression of molecuar markers of plasticity. These changes may rflect adaptive rsponses to physiological activation. © 1996 Wiley-Liss, Inc. |
