Wp. Few et Hh. Zakon, Androgens alter electric organ discharge pulse duration despite stability in electric organ discharge frequency, HORMONE BEH, 40(3), 2001, pp. 434-442
Weakly electric fish in the genus Sternopygus emit a sinusoidal, individual
ly distinct, and sexually dimorphic electric organ discharge (EOD) that is
used in electrolocation and communication. Systemically applied androgens d
ecrease EOD frequency, which is set by a medullary pacemaker nucleus, and i
ncrease pulse duration, which is determined by the cells of the electric or
gan (the electrocytes), in a coordinated fashion. One possibility is that a
ndrogens broaden the EOD pulse duration by acting on the pacemaker neurons,
thereby effecting a change in pacemaker firing frequency, and that the cha
nge in EOD pulse duration is due to an activity-dependent process. To deter
mine whether androgens can alter pulse duration despite a stable pacemaker
nucleus firing frequency, we implanted small doses of dihydrotestosterone i
n the electric organ. We found that androgen implants increased EOD pulse d
uration, but did not influence EOD frequency. In addition, using immunocyto
chemistry, we found that electrocytes label positively with an androgen rec
eptor antibody. While it is not known on which cells androgens act directly
, together these experiments suggest that they likely act on the electrocyt
es to increase EOD pulse duration. Since pulse duration is determined by el
ectrocyte action potential duration and ionic current kinetics, androgens m
ay therefore play a causative role in influencing individual variation and
sexual dimorphism in electrocyte electrical excitability, an important comp
onent of electrocommunicatory behavior. (C) 2001 Academic Press.