Tanaka E, Niiyama S, Uematsu K, Yokomizo Y, Higashi H
Department of Physiology, Kurume University School of Medicine, 67 Asahi-machi, Kurume, 830-0011, Japan.
Life Sci. 2002 Dec 20;72(4-5):363-74. doi: 10.1016/s0024-3205(02)02282-8.
Superfusion with an oxygen and glucose deprived medium (in vitro ischemia) of rat hippocampal CA1 pyramidal neurons in tissue slices produced a rapid depolarization within 5 min and thereafter showed no functional recovery (irreversible membrane dysfunction), even if oxygen and glucose were reintroduced. We previously suggested that such a rapid depolarization is triggered by the accumulation of extracellular glutamate (Glu). As a result, we examined the effects of either the activation or inhibition of presynaptic receptors, which modulate Glu release from the nerve terminal, on the potential change produced by in vitro ischemia. The adenosine A1 receptor antagonist, 8-cyclopenthyl theophylline, A2a receptor antagonist, ZM241385, and A2b receptor antagonist, alloxazine, did not significantly alter either the latency or the maximal slope of the rapid depolarization. In addition, the GABAB receptor antagonist, 2-hydroxysaclofen, or the metabotropic Glu receptor type 4 antagonist, alpha-methylserine-O-phosphate, did not change either the latency or the maximal slope. The adenosine A(1) receptor agonist, 2-chloro-N6-cyclopentyladenosine, A2a receptor agonist, CGS2168, or A2b receptor agonist, 5'-(N-ethylcarboxamido)-adenosine, did not affect these parameters either. None of these drugs restored the membrane potential to the pre-exposure level after the reintroduction of oxygen and glucose. Simultaneous intracellular recordings from CA1 and CA3 pyramidal neurons in the same slices revealed the membrane of the CA3 neurons to be hyperpolarized when a rapid depolarization occurred in the CA1 neurons. These results suggest that presynaptic Glu release does not accelerate during the generation of the rapid depolarization induced by in vitro ischemia.
用缺氧缺糖培养基（体外缺血）对大鼠海马组织切片中的CA1锥体神经元进行灌流，5分钟内即可产生快速去极化，此后即使重新供氧和供糖，也不会出现功能恢复（不可逆的膜功能障碍）。我们之前认为，这种快速去极化是由细胞外谷氨酸（Glu）的积累引发的。因此，我们研究了调节神经末梢Glu释放的突触前受体激活或抑制对体外缺血产生的电位变化的影响。腺苷A1受体拮抗剂8-环戊基茶碱、A2a受体拮抗剂ZM241385和A2b受体拮抗剂咯嗪，均未显著改变快速去极化的潜伏期或最大斜率。此外，GABAB受体拮抗剂2-羟基舒氯芬或代谢型谷氨酸受体4拮抗剂α-甲基丝氨酸-O-磷酸，也未改变潜伏期或最大斜率。腺苷A(1)受体激动剂2-氯-N6-环戊基腺苷、A2a受体激动剂CGS2168或A2b受体激动剂5'-(N-乙基甲酰胺基)-腺苷，也未影响这些参数。重新供氧和供糖后，这些药物均未使膜电位恢复到暴露前水平。对同一切片中的CA1和CA3锥体神经元同时进行细胞内记录发现，当CA1神经元发生快速去极化时，CA3神经元的膜会发生超极化。这些结果表明，在体外缺血诱导的快速去极化过程中，突触前Glu释放并未加速。
