RT Journal Article
SR Electronic
T1 A sex difference in synaptic efficacy at the laryngeal neuromuscular junction of Xenopus laevis
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 1660
OP 1668
DO 10.1523/JNEUROSCI.15-03-01660.1995
VO 15
IS 3
A1 ML Tobias
A1 DB Kelley
A1 M Ellisman
YR 1995
UL http://www.jneurosci.org/content/15/3/1660.abstract
AB Under physiological conditions, the response of Xenopus laevis laryngeal muscle fibers to nerve stimulation is sexually differentiated; subthreshold potentials are common in males and rare in females. This sex difference in muscle fiber response is correlated with sex differences in vocal behavior. Quantal analyses at male and female laryngeal synapses were performed to determine if there is a sex difference in synaptic strength. Quantal content at laryngeal synapses is significantly higher in females than in males. Values for quantal content in males can be increased by raising extracellular calcium concentration. There is no sex difference in miniature endplate potential amplitude suggesting that ACh receptor number or properties are not different in the sexes. Sex difference in synaptic strength thus appear presynaptic in origin; transmitter release is less in males. Ultrastructural analyses of the laryngeal motor terminal indicate that there is no sex difference in the length of active zones or in the number of channels per length of active zone. Thus, ultrastructural characteristics of the laryngeal motor terminal do not account for the pronounced sex difference in quantal content.