Testosterone fails to save androgen-sensitive rat motoneurons following early target removal.
Axotomy during development can result in the death of up to 100% of the affected motoneurons. However, axotomy-induced death can be significantly reduced by administration of androgens in young rats. Motoneuron death in the spinal nucleus of the bulbocavernosus (SNB) has previously been shown to be regulated by androgens during development. the present experiment examined the effects of androgen treatment on the survival of SNB motoneurons after target removal and concomitant axotomy early in development. On the day of birth, two target muscles of SNB motoneurons of male and female rats were bilaterally extirpated. Target removal resulted in a dramatic loss of SNB motoneurons within 48 h of surgery, with an ultimate loss of virtually all motoneurons projecting to the extirpated muscles by postnatal day 10. Treatment with testosterone failed to save SNB motoneurons from target removal-induced death. Pups treated with testosterone after target removal did not differ in the pattern or timing of motoneuron loss from untreated pups at any age examined. Counts of degenerating cells in the SNB reflected the extensive motoneuron loss and also did not differ with testosterone treatment. These results indicate that testosterone cannot save the androgen-sensitive SNB motoneurons from death after target removal and concomitant axotomy early in development. The failure of testosterone treatment to rescue SNB motoneurons in the absence of the SNB target musculature further suggests that during normal development, both androgens and target muscles are necessary for SNB motoneuron survival.
Kurz
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EM
Program in Neural Science, Indiana University, Bloomington 47405.
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Sengelaub
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D000728:Androgens / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000502:physiology*; D002470:Cell Survival / Q000187:drug effects; D003714:Denervation; D005260:Female; D008297:Male; D009046:Motor Neurons / Q000166:cytology* / Q000502:physiology; D009409:Nerve Crush; D009434:Neural Pathways / Q000502:physiology; D051381:Rats; D013116:Spinal Cord / Q000166:cytology* / Q000502:physiology; D013739:Testosterone / Q000494:pharmacology*
D000728:Androgens; D013739:Testosterone