Molecular bases of sympathetic innervation and developmental changes in ion channels

(1)交感神经支配介导蛋白交感神经束密集地支配第二伸肌，但不支配骨骼肌。培养时交感神经纤维密集分布于第二伸肌的基底上，而避开骨骼肌的基底。从心肌细胞条件培养液中纯化了引起交感神经纤维密集分布的蛋白质作为底物。在非还原和还原条件下，最纯化的组分在SDS-PAGE上显示单一条带，表观分子量为370，000道尔顿。在心肌细胞条件培养液中制备抗血清。鸡皮下注射抗血清可抑制6-羟基多巴胺诱导的外周组织（心、脾、肾和血管）轴突切断后肾上腺素能纤维的再生。结果提示，该蛋白可能参与了损伤交感神经纤维的再支配过程 ...更多信息 在小鸡体内的目标组织上。(2)电压敏感性离子通道的发育性变化采用全细胞电压钳技术，观察了小鼠趾短屈肌单纤维不同类型的Ca^<2 +>通道Ba^<2 +>电流、Na^+电流和内向整流K^+电流的发育性变化。出生后第1天（P1）分离的肌纤维显示瞬时电流I（Ca，T）和持续电流I（Ca，S）。I（Ca，T）在前30天内由P17检测不到，I（Ca，S）增加了4倍。失神经支配并不能阻止I（Ca，T）的消失。Geographutoxin II（GTX）区分GTX敏感，I（Na，s），和GTX抗性，I（Na，r）电流。I（Na，r）在P16时检测不到。I（Na，s）在前20天增加了15倍。在失神经支配的肌纤维I（Na，r）的增加高于正常纤维的水平。瞬时整流电流分为三个分量，I（稳态），I（上升）和I（衰减）。I（衰变）在整个产后发育过程中观察到。I（稳态）和I（升高）在P12后变得明显。失神经抑制I（稳态）和I（上升）的增加。我们的结论是，不同类型的离子通道电流在肌肉纤维中经历了戏剧性的变化，在他们的数量以及他们的属性由几个星期后出生。有些变化是在神经支配的控制下发生的，但另一些变化则不受神经支配的影响。少

(1) SYMPATHETIC INNERVATION-MEDIATING PROTEIN Sympathetic nerve fibirs densely innervate expansor secundariorum muscle, but not skeletal muscle. In cilture sympathetic nerve fibers densely distributed on the substrate from expansor secundariorum but avoided distributing on the substrate from skeletal muscle. The protein which caused the dense distribution of sympathetic fibers as the substrate has been purified from heart cell conditioned medium. The most purified fraction showed single band with apparent molecular weight of 370,000 daltons on SDS-PAGE under non-reducing and reducing conditions. Antiserum was raised against the factor in heart cell conditioned medium. Subcutaneous injection of the antiserum into the chick inhibited the regeneration of adrenergic fibers following 6-hydroxydopamine-induced axotomy in peripheral tissues (heart, spleen, kidney and blood vessel). The results indicate that the protein may function in the process of reinnervation of lesioned sympathetic fiber … More s on target tissues in the chick.(2) DEVELOPMENTAL CHANGES OF VOLTAGE-SENSITIVE ION CHANNELS The whole-cell voltage-clamp technique was used to examine developmental changes in different types of Ba^<2+> currents through Ca^<2+> channels, Na^+ currents and inward rectifier K^+ currents in single fibres isolated from mouse flexor digitorum brevis muscle. The muscle fibres isolated on day 1 post-natal (P1) showed transient, I(Ca,T), and sustained currents, I(Ca,S). I(Ca,T) became undetectable by P17 and I(Ca,S) increased four-fold in the first 30 days. Denervation did not prevent the disappearance of I(Ca,T). Geographutoxin II(GTX) distinguished GTX-sensitive, I(Na,s), and GTX-resistant, I(Na,r) currents. I(Na,r) became undetectable by P16. I(Na,s) increased 15-fold in the first 20 days. In denervated muscle fibres I(Na,r) was increased above the level of normal fibers. Inwardly rectifying current was split into three components, I(steady-state), I(rise) and I(decay). I(decay) was observed throughout post-natal development. I(steady-state) and I(rise) became apparent after P12. Denervation depressed the increase of I(steady-state) and I(rise). We conclude that different types of ion channel currents in the muscle fibres undergo dramatic changes in their numbers as well as their properties by a few weeks after birth. Some changes are under the control of innervation, but others occur independent of innervation. Less