NMDA receptor activation in the aged rat hippocampus.
Age-related alterations of N-methyl-D-aspartate receptor (NMDAr) activation were investigated in the CA1 field of hippocampal slices from young (3-6 months old) and aged (25-33 months old) Sprague-Dawley rats by using ex vivo extracellular electrophysiological recording techniques. NMDAr-mediated field excitatory postsynaptic potentials (fEPSPs) were induced by electrical stimulation of glutamatergic fibers in a magnesium (Mg(2+))-free medium supplemented with the non-NMDAr antagonist CNQX. The fEPSPs were significantly smaller in aged rats, whereas the response of presynaptic afferent fibers remained unaffected. No significant age-related differences were found in the ability of Mg(2+) to depress the magnitude of NMDAr-mediated fEPSPs. The responsiveness of postsynaptic NMDAr to the agonist was assessed in both groups of animals. No age-related differences were recorded either in the depolarizing effect of bath-applied NMDA or in the magnitude of the depolarization after altering extracellular Mg(2+) concentration. Finally, short-term potentiation (STP) of excitatory transmission was studied in young and aged rats considering the pivotal role of NMDAr in synaptic plasticity. No age-related alterations of the magnitude and the time course of STP in response to 10 or 30Hz conditioning stimulation were found. Because of the decrease in the magnitude of NMDAr-mediated synaptic transmission in aged animals, the absence of obvious modifications of synaptic plasticity suggests the occurrence of compensatory mechanisms that are discussed.
Potier
B
B
Dynamique des Systèmes Neuroendocriniens, INSERM U159, 2ter rue d'Alesia, 75014, Paris, France.
Poindessous-Jazat
F
F
Dutar
P
P
Billard
J M
JM
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000375:Aging / Q000502:physiology*; D000818:Animals; D004594:Electrophysiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D016202:N-Methylaspartate / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D013569:Synapses / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D016202:N-Methylaspartate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D008274:Magnesium