Adenosine modulates synaptic plasticity in hippocampal slices from aged rats

Adenosine is known to modulate synaptic plasticity in the hippocampus of yo ung animals through activation of adenosine A(1) receptors. The objective o f the present study is to investigate whether the modulatory role of adenos ine on phenomena of synaptic plasticity is maintained or modified in the hi ppocampus of aged animals. We compared the effects of the selective adenosi ne A(1) receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX, 50 nM), on paired-pulse facilitation (PPF), long-term depression (LTD), long-t erm potentiation (LTP) and depotentiation elicited in hippocampal slices ta ken from young adult (5-6 weeks) and old (2 years old) male Wistar rats. DP CPX attenuated PPF both in young (1.64 +/- 0.05 vs. 1.76 +/- 0.05%, n = 6) and in old rats (1.33 +/- 0.05 vs. 1.55 +/- 0.1%, n = 6). LTD was only obse rved in the presence of DPCPX in both young (21.3 +/- 0.6%, n = 4) and old rats (14.4 +/- 0.9%, n = 6). LTP induced by high-frequency stimulation (HFS ) was not significantly different in young and old animals, in the presence or in the absence of DPCPX. A larger depotentiation was observed in the pr esence of DPCPX in young rats (27.6 +/- 4.4% vs. 16.8 +/- 4.7%, PI = 7) as well as in old rats (41.3 +/- 5.1% vs. 16.1 +/- 2.7%, n = 6). LTP induced b y theta-burst stimulation was observed only in the presence of DPCPX (53.9 +/- 4.9%, n = 5) in young rats, but could be obtained either in the control solution (81.8 +/- 17.9%, n = 7) or in the presence of DPCPX (98.5 +/- 24. 2%, n = 7) in old rats. The modulatory role of endogenous adenosine on syna ptic plasticity is generally maintained in aged animals. Drugs interfering with adenosine A(1) receptor effects could then be used in old animals to m odify synaptic plasticity with relevant behavioural consequences. (C) 1999 Elsevier Science B.V. All rights reserved.