Harris E W, Cotman C W
Brain Res. 1985 May 20;334(2):348-53. doi: 10.1016/0006-8993(85)90230-6.
The effects of different synaptic antagonists on paired-pulse plasticity of medial perforant path responses were studied in rat hippocampal slices. Baclofen reduces the response to activation of the perforant path, but does not have the same net effect on the first and second responses to paired stimulation: baclofen lessens the percent paired-pulse depression of medial perforant path responses. Furthermore, at doses that reduced the control medial perforant path response by half, paired-pulse plasticity changed from paired-pulse depression to paired-pulse potentiation. A similar effect on medial perforant path paired-pulse plasticity is produced by decreasing extracellular calcium concentration. Kynurenic acid reduces the first and second responses to paired stimulation proportionately the same, and, therefore, has no effect on the percent paired-pulse depression. These results suggest that baclofen acts presynaptically to reduce the synaptic response, whereas kynurenate acts postsynaptically. Adenosine was also found to be a potent antagonist of medial perforant path responses, with effects on paired-pulse plasticity similar to baclofen: a new synaptic antagonist, N-p-chlorobenzoyl-piperazine-2,3-dicarboxylate, was found to have effects like kynurenate, suggesting that it is also a postsynaptic receptor blocker.
在大鼠海马切片中研究了不同突触拮抗剂对内侧穿通通路反应的双脉冲可塑性的影响。巴氯芬可降低对穿通通路激活的反应，但对双脉冲刺激的第一和第二个反应没有相同的净效应：巴氯芬可减轻内侧穿通通路反应的双脉冲抑制百分比。此外，在将对照内侧穿通通路反应降低一半的剂量下，双脉冲可塑性从双脉冲抑制转变为双脉冲增强。降低细胞外钙浓度对内侧穿通通路双脉冲可塑性产生类似影响。犬尿氨酸按比例同等程度降低对双脉冲刺激的第一和第二个反应，因此，对双脉冲抑制百分比没有影响。这些结果表明，巴氯芬通过突触前作用来降低突触反应，而犬尿酸则通过突触后作用。还发现腺苷是内侧穿通通路反应的有效拮抗剂，对双脉冲可塑性的影响与巴氯芬类似：发现一种新的突触拮抗剂N-对氯苯甲酰基哌嗪-2,3-二羧酸酯具有与犬尿酸类似的作用，表明它也是一种突触后受体阻滞剂。
