Université de Bordeaux, Centre National de la Recherche Scientifique, Centre de Neurosciences Intégratives et Cognitives, Biologie Animale, 33405 Talence Cedex, France.
J Neurosci. 2010 Apr 21;30(16):5603-16. doi: 10.1523/JNEUROSCI.0367-10.2010.
The excitability of the leg postural circuit and its response to serotonin (5-HT) were studied in vitro in thoracic nervous system preparations of dominant and subordinate male crayfishes. We demonstrate that the level of spontaneous tonic activity of depressor and levator motoneurons (MNs) (which control downward and upward movements of the leg, respectively) and the amplitude of their resistance reflex are larger in dominants than in subordinates. Moreover, we show that serotonergic neuromodulation of the postural circuit also depends on social status. Depressor and levator MN tonic firing rates and resistance reflex amplitudes were significantly modified in the presence of 10 mum 5-HT in dominants but not in subordinates. Using intracellular recording from depressor MNs, we show that their input resistance was not significantly different in dominants and subordinates in control conditions. However, 5-HT produced a marked depolarization in dominants and a significantly weaker depolarization in subordinates. Moreover, in the presence of 5-HT, the amplitude of the resistance reflex and the input resistance of MNs increased in dominants and decreased in subordinates. The peak amplitude and the decay phase of unitary EPSPs triggered by sensory spikes were significantly increased by 5-HT in dominants but not in subordinates. These observations suggest that neural networks are more reactive in dominants than in subordinates, and this divergence is even reinforced by 5-HT modulation.
我们在优势和从属雄性螯虾的胸部神经系统标本中研究了腿部姿势回路的兴奋性及其对 5-羟色胺（5-HT）的反应。我们证明，降压和升动机神经元（MNs）（分别控制腿部的向下和向上运动）的自发紧张活动水平及其阻力反射的幅度在优势个体中大于从属个体。此外，我们还表明，姿势回路的 5-羟色胺能调制也取决于社会地位。在优势个体中，存在 10 mum 5-HT 时，降压和升动机 MN 的紧张放电率和阻力反射幅度显著改变，但在从属个体中则不然。通过从降压 MN 进行细胞内记录，我们表明它们的输入电阻在对照条件下在优势个体和从属个体之间没有显著差异。然而，5-HT 在优势个体中产生明显的去极化，而在从属个体中则产生较弱的去极化。此外，在 5-HT 存在下，MN 的阻力反射幅度和输入电阻在优势个体中增加，而在从属个体中降低。由感觉刺触发的单位 EPSP 的峰值幅度和衰减相在优势个体中被 5-HT 显著增加，但在从属个体中则不然。这些观察结果表明，神经网络在优势个体中比在从属个体中更具反应性，而这种差异甚至因 5-HT 调制而得到加强。
