Pharmacological Protection of Synaptic Function, Spatial Learning, and Memory from Transient Hypoxia in Rats

Hypoxia significantly reduced cholinergic activity in rat CA1 field and intracellular in the CA1 pyramidal cells, recorded in hippocampal slices. The hypoxic responses of the hippocam-pal CA1 pyramidal cells to a brief hypoxia consisted of a short period of “synaptic arrest”, observed as an elimination of exci-tatory postsynaptic current under voltage clamp and recovered immediately as oxygenation was reinitiated. The hypoxic syn-aptic arrest was not associated with reduced postsynaptic responses of the pyramidal cells to externally applied L-gluta-mate, suggesting that the synaptic arrest might result from a presynaptic mechanism. The hypoxic synaptic arrest was abol-ished in the presence of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), a specific adenosine A1 receptor antagonist. Blocking adenosine A1 receptors also eliminated effects of hypoxia o