Teruyama R, Armstrong W E
Department of Anatomy and Neurobiology, College of Medicine, University of Tennessee, Memphis, TN 38163, USA.
J Neuroendocrinol. 2002 Dec;14(12):933-44. doi: 10.1046/j.1365-2826.2002.00844.x.
To better understand the plasticity of intrinsic membrane properties of supraoptic magnocellular neuroendocrine cells associated with reproductive function, intracellular recordings were performed in oxytocin (OT) and vasopressin (VP) neurones from virgin, late pregnant (E19-22), and lactating (8-12 days of lactation) rats in vitro, using hypothalamic explants. OT neurones from virgin rats displayed a narrower spike width than neurones from pregnant and lactating rats, characterized by faster rise and decay times. Spike width changes in VP neurones were not as prominent as those observed in OT neurones. In OT neurones, the amplitude and the decay of the afterhyperpolarization following spike trains was significantly larger and faster, respectively, in pregnant and lactating rats compared to virgin rats. These properties did not change during pregnancy and lactation in VP neurones. The incidence of the depolarizing afterpotential following spikes significantly increased from approximately 20% in virgin rats to 40-50% during pregnancy and lactation in OT neurones, but was stable (80-90%) across states in VP neurones. Repetitive firing properties (frequency adaptation, the first interspike interval frequency and frequency-current (F-I) relationship) were altered during pregnancy and lactation in OT neurones, but not VP neurones. The increased incidence of depolarizing afterpotentials in OT neurones enhances excitability, while the increased afterhyperpolarization results in suppression of firing rate. Thus, the changes may favour the short bursting activity seen in OT neurones during lactation. These results confirmed reproductive state-dependent changes in intrinsic membrane properties of OT neurones during lactation, and suggest these changes are in place during late pregnancy. This argues that the plasticity in the electrical properties in OT neurones associated with lactation is not instigated by suckling.
为了更好地理解与生殖功能相关的视上核大细胞神经内分泌细胞内在膜特性的可塑性，我们使用下丘脑外植体，对来自处女鼠、妊娠晚期（胚胎期19 - 22天）和哺乳期（哺乳8 - 12天）大鼠的催产素（OT）和加压素（VP）神经元进行了体外细胞内记录。处女鼠的OT神经元的动作电位宽度比妊娠和哺乳期大鼠的神经元窄，其特征是上升和衰减时间更快。VP神经元的动作电位宽度变化不如OT神经元明显。在OT神经元中，与处女鼠相比，妊娠和哺乳期大鼠在一串动作电位后的超极化后电位的幅度和衰减分别显著更大和更快。这些特性在VP神经元的妊娠和哺乳期没有变化。OT神经元中动作电位后去极化电位的发生率从处女鼠的约20%显著增加到妊娠和哺乳期的40 - 50%，但VP神经元在不同状态下保持稳定（80 - 90%）。妊娠和哺乳期OT神经元的重复放电特性（频率适应性、首个峰峰间期频率和频率 - 电流（F - I）关系）发生了改变，但VP神经元没有。OT神经元去极化后电位发生率的增加增强了兴奋性，而超极化后电位的增加导致放电率受到抑制。因此，这些变化可能有利于哺乳期OT神经元中出现的短串发放活动。这些结果证实了哺乳期OT神经元内在膜特性存在生殖状态依赖性变化，并表明这些变化在妊娠晚期就已出现。这表明与哺乳相关的OT神经元电特性的可塑性不是由哺乳引发的。
