Bhandari R N, Carter T L, Houghton A K, Clarke R W
Division of Animal Physiology, School of Biological Sciences, University of Nottingham, Loughborough, UK.
Neuroscience. 1999 Apr;90(1):191-9. doi: 10.1016/s0306-4522(98)00425-4.
The expression of Fos-like immunoreactivity has been studied in spinal segments L5-S1 of decerebrated, unanaesthetized, but otherwise unstimulated rabbits. The aim of the study was to establish baseline levels of Fos in such preparations, and to examine how these might change after spinalization and opioid receptor blockade. In animals with an intact spinal cord, approximately 30 Fos-positive profiles per section were found in the superficial dorsal horns (i.e. laminae I and II) of each 40-microm section, while about 20 profiles per section were found immediately adjacent to the central canal (lamina X). Fos-like immunoreactive profiles were rare elsewhere in the gray matter. When the spinal cord was sectioned at L1 (after blockade with local anaesthetic), significantly more Fos-like immunoreactivity was found in superficial and central regions of the gray matter (approximately 90 profiles per section) in animals perfused 4 h after decerebration, but not when perfusion was performed 2 or 8 h after decerebration. The opioid antagonist naloxone (0.25 mg/kg/h) had little effect on expression of Fos-like immunoreactivity in spinalized preparations, but significantly increased the numbers of Fos-positive profiles in all but the ventral areas of the spinal gray matter in non-spinalized preparations. The present data show that spinal section induces a transient increase in expression of Fos in the superficial and central parts of the spinal gray matter. It appears that spinalization induces spontaneous activity in some neurons in these regions of the cord, presumably as a result of relief of descending inhibition. The effects of naloxone indicate that endogenous opioids exert tonic inhibition over Fos-expressing spinal neurons in non-spinalized rabbits.
在去大脑、未麻醉但未受其他刺激的兔L5 - S1脊髓节段中，研究了Fos样免疫反应性的表达。本研究的目的是确定此类标本中Fos的基线水平，并研究脊髓横断和阿片受体阻断后这些水平可能如何变化。在脊髓完整的动物中，每40微米切片的浅背角（即I层和II层）中，每个切片大约有30个Fos阳性细胞，而紧邻中央管（X层）处每个切片约有20个细胞。灰质其他部位Fos样免疫反应性细胞很少。当在L1水平切断脊髓（局部麻醉阻断后），在去大脑后4小时灌注的动物中，灰质浅部和中央区域发现显著更多的Fos样免疫反应性（每个切片约90个细胞），但在去大脑后2小时或8小时灌注时则未发现。阿片拮抗剂纳洛酮（0.25mg/kg/h）对脊髓横断标本中Fos样免疫反应性的表达影响很小，但在未脊髓横断的标本中，除脊髓灰质腹侧区域外，显著增加了Fos阳性细胞的数量。目前的数据表明，脊髓横断可导致脊髓灰质浅部和中央部分Fos表达的短暂增加。似乎脊髓横断诱导了脊髓这些区域一些神经元的自发活动，推测是下行抑制解除的结果。纳洛酮的作用表明，内源性阿片类物质对未脊髓横断兔中表达Fos的脊髓神经元发挥着紧张性抑制作用。
