Objective To investigate the characteristics and possibility of using an image analyzer-aided method to count axotomized retinal ganglion cells (RGCs). Methods The left optic nerves of 18 rats were transected intraorbitally and a piece of gelform soaked in 5% fluorogold was applied to the ocular stump to retrogradely label the surviving RGCs. All animals were executed 2, 7 or 14 days after the operation (n=6 for each time point), respectively. The left retinae were removed, post-fixed and whole-mounted on the slides. The numbers of labeled RGCs were counted using both the conventional sampling method and image analysis, and compared statistically between the two methods. Results The number of surviving RGCs decreased sharply [(12 0663?9 089), (59 285?17 071) and (17 802?19 84) cells/mm 2 for image analyzer-aided method, and (118 237?7 898), (57 648?14 533) and (18 070?1 461) cells/mm 2 for conventional sampling method] when the survival time increased from 2 to 7 and 14 days. No significant difference was detected between the two groups at any corresponding time points. Conclusion The image analyzer-aided method is convenient, objective and reproducible, which can be used in the studies where counting RGCs is needed.

FOS protein in the lumbosacral spinal cord of the rat was detected to study neuronal activation induced by noxious stimulation of the urethra. In rats receiving infusion of 100 μl of 2% formalin into the urethra, a large number of FOS-positive neurons were seen in the lumbosacral cord segments (L6 and S1), and they were primarily distributed in the medial dorsal horn and dorsal commissural nucleus. Nearly all of FOS expression was blocked by bilateral transection of the pudendal nerve, whereas bilateral transection of the pelvic nerve seemed to have no obvious effect on FOS expression.Behavioral changes were also observed in the nerve-transected rats. Bilateral pelvic nerve-transected rats showed frequently licking of the external urethral orifice after application of the irritant to the urethra, which was quite similar to that of the nerve-intact rats. Such behavior completely disappeared in the rats receiving bilateral pudendal nerve transection. The results suggest that the medial dorsal horn and dorsal commissural nucleus in the L6 and S1 segments are involved in processing nociceptive inputs from the urethra, which is carried by the pudendal nerve.