Serotonin has different effects on two classes of Betz cells from the cat.
Serotonin has different effects on two classes of Betz cells from the cat.
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血清素对猫的两类 Betz 细胞有不同的影响。
DOI：
10.1152/jn.1994.72.4.1925
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发表时间：
1994
影响因子：
2.5
通讯作者：
Spain,WJ
中科院分区：
文献类型：
--
作者：
Spain,WJ
1. 体外猫 Betz 细胞的细胞内记录显示，血清素 (5-HT) 的主导作用与其发生的 Betz 细胞亚型之间存在很强的相关性。在表现出超极化后兴奋的大 Betz 细胞（称为 PHE 细胞）中，5-HT 引起持久的膜去极化，而 5-HT 在表现出超极化后抑制的较小 Betz 细胞（称为 PHI 细胞）中引起不同持续时间的初始超极化。 2.电压钳研究表明，5-HT引起阳离子电流Ih激活的去极化转变，从而导致PHE细胞去极化，而PHI细胞超极化是由静息钾电导增加引起的。 3. 在恒流刺激期间，5-HT 对放电特性的影响在两种类型的 Betz 细胞中也存在一致的差异。在 PHE 细胞中，施加 5-HT 后初始放电速率增加，但稳定放电不受影响。 Ih 激活的去极化偏移导致初始放电速率增加。 4.在PHI细胞中，5-HT导致尖峰频率适应能力下降。适应性的下降是由两种电导变化的组合引起的。首先，5-HT 会导致 PHI 细胞缓慢后去极化，在没有进一步刺激的情况下可能会引发重复放电。 sADP 依赖于钙通过电压门控通道的进入，并与膜电导的降低相关。其次，5-HT 导致缓慢的钙依赖性钾电流减少，该钾电流通常会导致缓慢的适应。 5. 总之，5-HT 对兴奋性的影响在 Betz 细胞亚型中存在系统性差异，部分原因是它们具有不同的受调节的主要离子机制。如果我们假设 PHE 细胞和 PHI 细胞分别代表快锥体束 (PT) 神经元和慢速锥体束 (PT) 神经元，则 5-HT 将导致快 PT 细胞的早期募集，并在低水平突触兴奋期间延迟慢 PT 细胞的募集。
1. Intracellular recording from cat Betz cells in vitro revealed a strong correlation between the dominant effect of serotonin (5-HT) and the Betz cell subtype in which it occurred. In large Betz cells that show posthyperpolarization excitation (termed PHE cells), 5-HT evoked a long-lasting membrane depolarization, whereas 5-HT evoked an initial hyperpolarization of variable duration in smaller Betz cells that show posthyperpolorization inhibition (termed PHI cells). 2. Voltage-clamp studies revealed that 5-HT caused a depolarizing shift of activation of the cation current Ih, which resulted in the depolarization in PHE cells, whereas the hyperpolarization in PHI cells is caused by an increase in a resting potassium conductance. 3. The effect of 5-HT on firing properties during constant current stimulation also differed consistently in the two types of Betz cells. In PHE cells the initial firing rate increased after 5-HT application, but the steady firing was unaffected. The depolarizing shift of Ih activation caused the increase of initial firing rate. 4. In PHI cells 5-HT caused a decrease in spike frequency adaptation. The decrease in adaptation was caused by a combination of two conductance changes. First, 5-HT caused a slow afterdepolarization in PHI cells that could trigger repetitive firing in the absence of further stimulation. The sADP depended on calcium entry through voltage-gated channels and was associated with a decrease in membrane conductance. Second, 5-HT caused reduction of a slow calcium-dependent potassium current that normally contributes to slow adaptation. 5. In conclusion, the effect of 5-HT on excitability differs systematically in Betz cell subtypes in part because they have different dominant ionic mechanisms that are modulated. If we assume that PHE cells and PHI cells represent fast and slow pyramidal tract (PT) neurons respectively, 5-HT will cause early recruitment of fast PT cells and delay recruitment of slow PT cells during low levels of synaptic excitation.