Counts of neurons in spinal cords.

<p><b>A</b>) Number of NeuN immunoreactive nuclei per section (mean ± SEM) in 10 mm segments centred on the injury site at different times after surgery (n = 3–4 animals for each group). For each animal, the average of 12–14 sections was determined. In sham-operated animals (open bars), there was little difference in number of neurons between 24 hours, 4 weeks and 10 weeks after surgery. In the injured animals, the number of neurons was significantly lower at 2 hours compared to sham controls (<i>p</i><0.05, *) and was further reduced at 24 h (<i>p</i><0.05, *). At 24 hours, 4 days, 4 weeks and 10 weeks, the number of neurons was significantly lower than in age matched sham controls (<i>p</i><0.01) and compared to 2 h after injury (<i>p</i><0.05). There was no significant change in the number of neurons from 24 hours to 10 weeks after injury. 2 h = 2 hours, 1d = 24 hours, 4d = 4 days, 4w = 4 weeks, 10w = 10 weeks. <b>B</b>) Number of NeuN neurons per section (mean ± SEM) in injured animals normalised to control animals at different distances from injury site (0 mm). At 2 hours after injury, the number of neurons was higher at each point along the cord compared to all later times after injury. There was little difference in neuron numbers at any point along the cord from 24 hours to 10 weeks after injury. Note the similar pattern of neuron loss rostral and caudal to the injury site. <b>C</b>) Number of grey matter neurons (immunoreactive for PGP9.5, NSE or NeuN) per section normalised to sham operated control animals in 10 mm segments centred on the injury site at different times after surgery. The similar neuron numbers from 24 hours to 10 weeks after injury indicate that the loss of grey matter neurons occurs within the first 24 hours. Data are mean ± SEM, n = 3–4 for each group.