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Synaptic changes in the perineal motoneurons of aged male rats
Author(s) -
Matsumoto Akira
Publication year - 1998
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/(sici)1096-9861(19981012)400:1<103::aid-cne7>3.0.co;2-d
Subject(s) - bulbocavernosus reflex , biology , motor neuron , somatic cell , neuron , horseradish peroxidase , anatomy , testosterone (patch) , central nervous system , androgen , synaptogenesis , endocrinology , medicine , spinal cord , neuroscience , hormone , biochemistry , enzyme , gene
Cholera toxin‐horseradish peroxidase (CT‐HRP) was injected into the bulbocavernosus muscles of young (2 months of age) and old (19–20 months of age) male rats, 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 120 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 young and old SNB motoneurons consisted of synaptic contacts. The mean percentage of somatic membranes covered by synapses in old rats was significantly smaller than that in young ones. Size and number of synaptic contacts per unit length of somatic membranes in old animals were also significantly reduced. Plasma levels of testosterone in old males were significantly smaller than those in young ones. These age‐related changes in synaptic inputs to SNB motoneurons and plasma levels of androgen seem to correlate with aging of the SNB system. J. Comp. Neurol. 400:103–109, 1998. © 1998 Wiley‐Liss, Inc.