Kiehn O, Sillar K T, Kjaerulff O, McDearmid J R
Section for Neurophysiology, Department of Physiology, The Panum Institute, 2200 Copenhagen N, Denmark.
J Neurophysiol. 1999 Aug;82(2):741-6. doi: 10.1152/jn.1999.82.2.741.
We have studied the effects of the biogenic amine noradrenaline (NA) on motor activity in the isolated neonatal rat spinal cord. The motor output was recorded with suction electrodes from the lumbar ventral roots. When applied on its own, NA (0.5-50 microM) elicited either no measurable root activity, or activity of a highly variable nature. When present, the NA-induced activity consisted of either low levels of unpatterned tonic discharges, or an often irregular, slow rhythm that displayed a high degree of synchrony between antagonistic motor pools. Finally, in a few cases, NA induced a slow locomotor-like rhythm, in which activity alternated between the left and right sides, and between rostral and caudal roots on the same side. As shown previously, stable locomotor activity could be induced by bath application of N-methyl-D-aspartate (NMDA; 4-8.5 microM) and/or serotonin (5-HT; 4-20 microM). NA modulated this activity by decreasing the cycle frequency and increasing the ventral root burst duration. These effects were dose dependent in the concentration range 1-5 microM. In contrast, at no concentration tested did NA have consistent effects on burst amplitudes or on the background activity of the ongoing rhythm. Moreover, NA did not obviously affect the left/right and rostrocaudal alternation of the NMDA/5-HT rhythm. The NMDA/5-HT locomotor rhythm sometimes displayed a time-dependent breakdown in coordination, ultimately resulting in tonic ventral root activity. However, the addition of NA to the NMDA/5-HT saline could reinstate a well-coordinated locomotor rhythm. We conclude that exogenously applied NA can elicit tonic activity or can trigger a slow, irregular and often synchronous motor pattern. When NA is applied during ongoing locomotor activity, the amine has a distinct slowing effect on the rhythm while preserving the normal coordination between flexors and extensors. The ability of NA to "rescue" rhythmic locomotor activity after its time-dependent deterioration suggests that the amine may be important in the maintenance of rhythmic motor activity.
我们研究了生物胺去甲肾上腺素（NA）对新生大鼠离体脊髓运动活性的影响。通过吸力电极从腰段腹根记录运动输出。单独应用时，NA（0.5 - 50微摩尔）要么未引发可测量的根活动，要么引发高度可变的活动。当出现NA诱导的活动时，其活动包括低水平的无模式强直放电，或者通常不规则的缓慢节律，这种节律在拮抗运动池之间表现出高度同步性。最后，在少数情况下，NA诱导出类似慢运动的节律，其中活动在左右两侧以及同侧的头端和尾端根之间交替。如先前所示，通过浴加N - 甲基 - D - 天冬氨酸（NMDA；4 - 8.5微摩尔）和/或5 - 羟色胺（5 - HT；4 - 20微摩尔）可诱导出稳定的运动活性。NA通过降低周期频率和增加腹根爆发持续时间来调节这种活动。在1 - 5微摩尔的浓度范围内，这些效应呈剂量依赖性。相反，在任何测试浓度下，NA对爆发幅度或正在进行的节律的背景活动均无一致影响。此外，NA并未明显影响NMDA/5 - HT节律的左右和头尾交替。NMDA/5 - HT运动节律有时会出现时间依赖性的协调性破坏，最终导致强直腹根活动。然而，向NMDA/5 - HT盐溶液中添加NA可恢复协调良好的运动节律。我们得出结论，外源性应用NA可引发强直活动或触发缓慢、不规则且通常同步的运动模式。当在正在进行的运动活动期间应用NA时，该胺对节律有明显的减慢作用，同时保持屈肌和伸肌之间的正常协调性。NA在其时间依赖性恶化后“挽救”节律性运动活动的能力表明，该胺可能在维持节律性运动活动中起重要作用。
