The present study labels the neuronal cell bodies that give rise to afferent fibers that innervate the bladder of cat and rat. The method used was the retrograde transport of horseradish peroxidase (HRP) from its injection site in the bladder to cells in the various dorsal root ganglia. In the rat, the labelled cells are located in the L1–L2 and L6–S1 dorsal root ganglia. In the cat, the labelled cells are located in the L2–L5 and S1–S4 dorsal root ganglia. This confirms older clinical findings, and for the first time directly demonstrates the afferent cell bodies for the bladder. The bladder afferents are small ganglion cells in both rat and cat, and because there is a correlation between the size of axon and the cell body from which it originates, we conclude that the great majority of bladder afferents are small myelinated or unmyelinated axons. In addition, by restricting the HRP to one side of the bladder, we were able to show that some afferent cell bodies send their distal processes across the midline. These results will be useful in considerations of the neural control of bladder function.
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