Age-Related Decrease in the Schaffer Collateral-Evoked EPSP in Awake, Freely, Behaving Rats

[摘要] Synaptic response size in the CA1 region ofthe hippocampus in aged rats is reduced for agiven stimulus intensity, compared with thatelicited in young rats. Consistent with the in vitrofindings of reduced Schaffer collateral-evokedCA1 EPSPs in old rats, the population currentsevoked to iontophoretically applied AMPA arealso smaller relative to the presynaptic fiberpotential amplitude. On the other hand, the size ofthe presynaptic fiber potential and amplitude ofunitary intra-cellularly recorded EPSP responsesdo not change across age in the CA1 region. Theseelectrophysiological findings are consistent withthe hypothesis that old rats have fewer functionalsynaptic contacts per Schaffer collateral axonthan do young rats. The possibility that this agechange arises as a result of a differential tissuerecovery response to in vitro preparation wasexamined in the present study. CA1 presynapticfiber potential and EPSP amplitudes evoked bythe stimulation of Schaffer collateral afferentswere studied in intact, freely behaving youngand old rats. We confirmed in vivo the pattern of electrophysiophysiological results previouslyreported in vitro and found significantcorrelations between the synaptic responseamplitudes and the accuracy of spatial behaviorin the Morris swim task. The data suggest thatchanges in functional connectivity of old ratsmay be a significant contributor to cognitivechanges during aging.

[学科分类] 精神健康和精神病学