Rcentage of GAP-43IR (76.59 61.49 ) migrating neurons from DRG explants in neuromuscular coculture is also higher than that in DRG explants culture alone (39.86 62.10 ) (P,0.001) (Fig. 7).Results Morphology of DRG neurons and SKM cells in neuromuscular coculturesIn the DRG explants cultures, the DRG explants sent large radial projections 
to the peripheral area. The axons formed a lacelike network 
with crossing patterns in the peripheral area. The single migrating neurons scattered in the space of the network and sent axons to join the network (Fig. 1). In neuromuscular coculture, most of SKM cells are fused to form myotubes which maybe branched or take the shape of long rods. The axons from DRG explant frequently. Some axons terminate upon contact with the contracting SKM cells, others may choose to ignore the surfaces of SKM cells. The axons would cross each other to form a fine network on the surface of the single layered SKM cells. The crossing axons adhere to each other hence the displacement of one TA01 terminal axon on a contracting muscle cell would also oscillate the proximally area of the axonal network. The configurations of the terminal axons observed under SEM were variable. Some axons would widen into a varicosity, some would become 548-04-9 site smaller in caliber and many others appear to be no different from the immediate proximal configuration. The endings enlarge and terminate on the surface of SKM cells to form neuromuscular junction (NMJ)-like structures (Fig. 1,2).The mRNA levels of NF-200 and GAP-To determine the mRNA levels of NF-200 and GAP-43, the DRG explants at 6 days of culture age in the presence or absence of SKM cells were analyzed by real time-PCR. NF-200 mRNA levels increased in neuromuscular cocultures 15481974 (1.7560.09 folds, P,0.001) as compared with that in DRG explants culture alone. Similarly, GAP-43 mRNA levels also increased in neuromuscular cocultures (2.0060.16 folds, P,0.01) as compared with that in DRG explants culture alone (Fig. 8).The protein levels of NF-200 and GAP-To determine the protein levels of NF-200 and GAP-43, the DRG explants at 6 days of culture age in the presence or absence of SKM cells were analyzed by Western blot assay. NF-200 protein levels increased in neuromuscular cocultures (1.4660.02 folds, P,0.001) as compared with that in DRG explants culture alone (Fig. 9). GAP-43 protein levels increased in neuromuscular cocultures (1.6860.04 folds, P,0.001) as compared with that in DRG explants culture alone, too (Fig. 15755315 10).DiscussionDuring development, neurons extend axons to their targets. The neurites’ survival then becomes dependent on the trophic substances secreted by their target cells [34]. Target tissues contribute to the phenotypic and functional development of sensory neurons [35?6]. The interdependence of sensory neurons and SKM cells has not been fully understood. To better understand the interactions between sensory neurons and SKM cells, neuromuscular cocultures of organotypic DRG explants and dissociate SKM cells were established in the present study. Using this culture system, the morphological relationship between DRG neurons and SKM cells, neurites growth and neuronal migration were investigated. The results reveal that DRG explants show denser neurites outgrowth in neuromuscular cocultures as compared with that in the culture of DRG explants alone. The number of total migrating neurons (the MAP-2-expressing neurons) and the percentage of NF-200-IR and GAP-43-IR neurons increased signif.Rcentage of GAP-43IR (76.59 61.49 ) migrating neurons from DRG explants in neuromuscular coculture is also higher than that in DRG explants culture alone (39.86 62.10 ) (P,0.001) (Fig. 7).Results Morphology of DRG neurons and SKM cells in neuromuscular coculturesIn the DRG explants cultures, the DRG explants sent large radial projections to the peripheral area. The axons formed a lacelike network with crossing patterns in the peripheral area. The single migrating neurons scattered in the space of the network and sent axons to join the network (Fig. 1). In neuromuscular coculture, most of SKM cells are fused to form myotubes which maybe branched or take the shape of long rods. The axons from DRG explant frequently. Some axons terminate upon contact with the contracting SKM cells, others may choose to ignore the surfaces of SKM cells. The axons would cross each other to form a fine network on the surface of the single layered SKM cells. The crossing axons adhere to each other hence the displacement of one terminal axon on a contracting muscle cell would also oscillate the proximally area of the axonal network. The configurations of the terminal axons observed under SEM were variable. Some axons would widen into a varicosity, some would become smaller in caliber and many others appear to be no different from the immediate proximal configuration. The endings enlarge and terminate on the surface of SKM cells to form neuromuscular junction (NMJ)-like structures (Fig. 1,2).The mRNA levels of NF-200 and GAP-To determine the mRNA levels of NF-200 and GAP-43, the DRG explants at 6 days of culture age in the presence or absence of SKM cells were analyzed by real time-PCR. NF-200 mRNA levels increased in neuromuscular cocultures 15481974 (1.7560.09 folds, P,0.001) as compared with that in DRG explants culture alone. Similarly, GAP-43 mRNA levels also increased in neuromuscular cocultures (2.0060.16 folds, P,0.01) as compared with that in DRG explants culture alone (Fig. 8).The protein levels of NF-200 and GAP-To determine the protein levels of NF-200 and GAP-43, the DRG explants at 6 days of culture age in the presence or absence of SKM cells were analyzed by Western blot assay. NF-200 protein levels increased in neuromuscular cocultures (1.4660.02 folds, P,0.001) as compared with that in DRG explants culture alone (Fig. 9). GAP-43 protein levels increased in neuromuscular cocultures (1.6860.04 folds, P,0.001) as compared with that in DRG explants culture alone, too (Fig. 15755315 10).DiscussionDuring development, neurons extend axons to their targets. The neurites’ survival then becomes dependent on the trophic substances secreted by their target cells [34]. Target tissues contribute to the phenotypic and functional development of sensory neurons [35?6]. The interdependence of sensory neurons and SKM cells has not been fully understood. To better understand the interactions between sensory neurons and SKM cells, neuromuscular cocultures of organotypic DRG explants and dissociate SKM cells were established in the present study. Using this culture system, the morphological relationship between DRG neurons and SKM cells, neurites growth and neuronal migration were investigated. The results reveal that DRG explants show denser neurites outgrowth in neuromuscular cocultures as compared with that in the culture of DRG explants alone. The number of total migrating neurons (the MAP-2-expressing neurons) and the percentage of NF-200-IR and GAP-43-IR neurons increased signif.