Fargo KN, Sengelaub DR (2002) Androgen manipulation protects remaining motoneurons from dendritic atrophy after induced motoneuron death. Neuroscience 2002 Abstracts 466.13. Society for Neuroscience, Orlando, FL.
Summary: Androgen treatment facilitates axon regrowth after axotomy of facial and sciatic motoneurons, and reverses castration-induced dendritic atrophy in motoneurons of the spinal nucleus of the bulbocavernosus (SNB) in rats. We assessed whether a similar therapeutic effect of androgen would be seen in dendrites following partial depletion of SNB motoneurons. We injected the toxin saporin, conjugated to choleratoxin (β-saporin), unilaterally into the SNB target muscles, bulbocavernosus (BC) and levator ani (LA), of two groups of adult male rats. One group had been castrated six weeks earlier to induce dendritic atrophy, and received testosterone-filled Silastic capsules coincident with β-saporin injection (SAP+T). The other group had no castration or androgen treatment (SAP-only). Four weeks after β-saporin injection, we injected choleratoxin conjugated HRP into the contralateral (non-saporin injected) BC muscle to label SNB motoneurons. A group of untreated normal males was also included. Cell counts were performed, and dendrites of HRP-labeled SNB motoneurons were reconstructed in three dimensions. β-saporin killed ~65% of motoneurons in the SNB ipsilateral to the saporin-injected muscles; contralateral SNB motoneuron numbers were not affected. SNB dendritic arbors on the non-saporin injected side were ~60% shorter in SAP-only animals compared to those of untreated males; in contrast, dendritic arbors in SAP+T animals were unaffected. These results indicate that a) motoneuron death causes dendritic atrophy in remaining SNB motoneurons, and that b) previous castration and concurrent testosterone replacement protects against this atrophy.
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