Fitzgerald M, Koltzenburg M
Brain Res. 1986 Jan;389(1-2):261-70. doi: 10.1016/0165-3806(86)90194-x.
The postnatal development of descending inhibition in the spinal cord has been studied in the rat. Electrophysiological recordings were made in neonatal rat pups of the activity in single lumbar dorsal horn cells evoked by stimulation of the skin of the hindlimb. Descending inhibition was tested by observing the effect of stimulation of the dorsolateral funiculus (DLF) at thoracic level on the dorsal horn cell responses. In adults the DLF is known to contain descending axons from the brainstem which inhibit dorsal horn cell activity. Such inhibition was always observed in days 22-24 rat pups. At 18 days of age it was present but required higher-intensity stimulation to produce an effect. On day 12 only half the dorsal horn cells tested were inhibited by DLF stimulation and then only weakly. On day 9 no cells were inhibited. Application of horseradish peroxidase to DLF axons in the lumbar cord resulted in retrograde labelling of cells in the medulla, pons and midbrain. The labelling on day 6 was comparable to the adult. The results show that despite the early anatomical existence of a descending DLF pathway, there is no functional descending inhibition until days 10-12 of life. It is suggested that this is due to delayed maturation of crucial interneurones in the dorsal horn or to insufficient levels of 5-hydroxytryptamine or other neurochemicals in the descending DLF axon terminals.
对大鼠脊髓下行抑制的产后发育进行了研究。在新生大鼠幼崽中，对后肢皮肤刺激诱发的单个腰段背角细胞活动进行电生理记录。通过观察胸段背外侧索（DLF）刺激对背角细胞反应的影响来测试下行抑制。已知在成体中，DLF包含来自脑干的下行轴突，这些轴突抑制背角细胞活动。在出生后22 - 24天的大鼠幼崽中总是观察到这种抑制。在18日龄时它存在，但需要更高强度的刺激才能产生效果。在12日龄时，仅一半被测试的背角细胞受到DLF刺激的抑制，而且抑制较弱。在9日龄时，没有细胞受到抑制。将辣根过氧化物酶应用于腰段脊髓的DLF轴突，导致延髓、脑桥和中脑的细胞逆行标记。6日龄时的标记与成体相当。结果表明，尽管早期在解剖学上存在下行DLF通路，但在出生后10 - 12天之前没有功能性的下行抑制。有人认为，这是由于背角关键中间神经元的成熟延迟，或者是下行DLF轴突终末中5 - 羟色胺或其他神经化学物质水平不足所致。
