title: Androgen stimulates neuronal plasticity in the perineal motoneurons of aged male rats.
abstract: Ten aged male rats (24 months of age) were castrated and implanted subcutaneously with Silastic capsules containing testosterone (T)(5 males) or nothing (5 males). Five sham-castrated males (25 months of age) served as controls. Four weeks after castration, cholera toxin-horseradish peroxidase (CT-HRP) was injected into the bulbocavernosus muscles and animals were killed 2 days later. The spinal cords containing the spinal nucleus of the bulbocavernosus (SNB) were dissected, processed with a modified tetramethylbenzidine method for visualization of retrogradely transported CT-HRP, and examined ultrastructurally. Neuronal structures apposing the membranes of 150 CT-HRP-labeled SNB motoneurons were analyzed by measuring the percentage of somatic membranes covered by synaptic contacts, synaptoid contacts, and neuron-neuron contacts. Most of the neuronal structures in the control and experimental SNB motoneurons consisted of synaptic contacts. The mean percentage of somatic membranes covered by synapses in castrated, aged males treated with T was significantly greater than that in control or castrated animals. Size and number of synaptic contacts per unit length of somatic membranes in castrated, aged males treated with T were also significantly greater than those in control or castrated animals. Plasma levels of T in castrated, aged males treated with T were significantly greater than that in controls. These results suggest that the SNB motoneurons of aged male rats retain a considerable synaptic plasticity in response to androgen, and that androgen may be, at least in part, involved in the process of aging of the SNB system in male rats.
authors.affiliation: Department of Anatomy, Juntendo University School of Medicine, Hongo, Tokyo 113-0033, Japan. akira@med.juntendo.ac.jp
authors.forename: A
authors.initials: A
authors.lastname: Matsumoto
mesh_terms: D000375:Aging / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D002369:Castration / Q000009:adverse effects; D002772:Cholera Toxin / Q000494:pharmacology; D005837:Genitalia, Male / Q000187:drug effects / Q000294:innervation / Q000502:physiology; D008297:Male; D009046:Motor Neurons / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000187:drug effects / Q000294:innervation / Q000378:metabolism; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D010502:Perineum / Q000294:innervation / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar / Q000033:anatomy & histology / Q000378:metabolism*; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D013569:Synapses / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D013739:Testosterone / Q000097:blood / Q000494:pharmacology*
chemical_list: D013739:Testosterone; D002772:Cholera Toxin