Moudy A M, Schwartzkroin P A
Department of Neurological Surgery, University of Washington, Seattle 98195.
Brain Res Dev Brain Res. 1992 May 22;67(1):57-66. doi: 10.1016/0165-3806(92)90025-r.
The development of hippocampal neuronal sensitivities to the beta-noradrenergic agent, isoproterenol, was examined in tissue from immature rats. The in vitro hippocampal slice preparation was used to assess intracellularly recorded responses from hippocampal neurons to pressure-pulse and bath application of noradrenergic drugs. Effects of the drug on individual hippocampal CA3 pyramidal neurons were compared across several stages of development, ranging from postnatal day 4-5 (P4-5) to maturity. Isoproterenol, pressure-pulse applied to CA3c pyramidal cells, produced a depolarization of membrane potential and an increase in cell input resistance in tissue as young as P7. Spike frequency adaptation (in trains of action potentials triggered by depolarizing pulses) was reduced, as were the slow after-hyperpolarizations following the spike trains. All agonist effects were blocked by timolol, a beta-antagonist. Drug-induced changes in cell membrane and firing properties in immature tissue were qualitatively similar to beta-receptor-mediated noradrenergic effects in adult tissue. These results indicate that the beta-receptor-mediated component of the noradrenergic effect in rat hippocampus is physiologically functional by the seventh day of postnatal life; at earlier times (P4-5) these beta-receptor-mediated noradrenergic actions are, at best, equivocal.
在未成熟大鼠的组织中，研究了海马神经元对β-去甲肾上腺素能药物异丙肾上腺素的敏感性发展情况。体外海马脑片制备用于评估海马神经元对压力脉冲和浴槽施加去甲肾上腺素能药物的细胞内记录反应。在从出生后第4 - 5天（P4 - 5）到成熟的几个发育阶段，比较了该药物对单个海马CA3锥体神经元的影响。对P7幼龄组织中的CA3c锥体神经元施加压力脉冲的异丙肾上腺素，可使膜电位去极化，并增加细胞输入电阻。峰频率适应性（在去极化脉冲触发的动作电位串中）降低，峰串后的慢后超极化也降低。所有激动剂效应均被β拮抗剂噻吗洛尔阻断。未成熟组织中药物诱导的细胞膜和放电特性变化在性质上与成年组织中β受体介导的去甲肾上腺素能效应相似。这些结果表明，大鼠海马中去甲肾上腺素能效应的β受体介导成分在出生后第7天具有生理功能；在更早的时期（P4 - 5），这些β受体介导的去甲肾上腺素能作用充其量是不明确的。
