The Journal of Neuroscience, November 15, 2000, 20(22):8586-8595
Androgen-Induced Changes in the Response Dynamics of Ampullary
Electrosensory Primary Afferent Neurons
Joseph A.
Sisneros and
Timothy C.
Tricas
Department of Biological Sciences, Florida Institute of Technology,
Melbourne, Florida 32901
Male stingrays use their ampullary electroreceptors to locate
mates, but the effect of gonadal androgens on electrosensory encoding
during the reproductive season is unknown. We tested the hypothesis
that gonadal androgens induce neurophysiological changes in the
electrosense of male Atlantic stingrays. During the primary androgen
increase in wild males, the electrosensory primary afferent neurons
show an increase in discharge regularity, a downshift in best frequency
(BF) and bandpass, and a greater sensitivity to low-frequency stimuli
from 0.01 to 4 Hz. Experimental implants of dihydrotestosterone in male
stingrays induced a similar lowered BF and bandpass and increased
average neural sensitivity to low-frequency stimuli (0.5-2 Hz) by a
factor of 1.5. Primary afferents from long ampullary canals (>3 cm)
were more sensitive and had a lower bandpass and BF than did afferents
from short canals (<2 cm). We propose that these androgen-induced
changes in the frequency response properties of electrosensory
afferents enhance mate detection by male stingrays and may ultimately
increase the number of male reproductive encounters with females.
Furthermore, differences in primary afferent sensitivity among short
and long canals may facilitate detection, orientation, and localization of conspecifics during social interactions.
Key words:
ampullae of Lorenzini; androgen; elasmobranch; electroreceptor; DHT; frequency response
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