XXXX -induced changes in electrocommunicatory behavior are correlated with changes in substance P-like immunoreactivity in the brain of the electric fish Apteronotus leptorhynchus.

@entity3800 @entity146 @entity342 @entity3507
The hormonal regulation of sex differences in electrocommunicatory behavior and brain substance P-like immunoreactivity ( @entity3507 -ir) were examined in the weakly electric fish, Apteronotus leptorhynchus. This animal modulates its electric organ discharge (EOD) to produce discrete electric social signals (chirps), which function in @entity146 . Males readily chirp in response to electrosensory stimuli that mimic the presence of a conspecific; females also chirp in response to such stimuli, but do so at much lower rates than males. We have recently demonstrated that @entity342 treatment enhances chirping behavior in females and may also lead to a change in chirp quality or structure. In this study, we quantified @entity342 -induced changes in chirp structure and simultaneously examined whether @entity3800 alter the sexually dimorphic pattern of @entity3507 -ir in a brain region (prepacemaker nucleus, PPn) known to control chirping. Our results demonstrate that, in females, @entity3800 cause both the induction of chirping and an alteration of chirp structure; chirps recorded from @entity342 -implanted females had longer durations and more dramatic frequency and amplitude modulations compared to controls, and appear similar to those reported to be produced during spawning. Moreover, @entity342 -induced changes in chirping are correlated with increased expression of @entity3507 -ir within specific brain nuclei of females. These changes may underly behavioral changes in chirping, since treated females showed a male-like pattern of @entity3507 -ir in the PPn. However, alterations in @entity3507 -ir were not restricted to the PPn, but also occurred in diencephalic regions related to pituitary function and reproductive behavior. The results suggest that @entity3800 modulate chirping activity and cause both specific and wide-spread changes in @entity3507 -ir that may relate to a functional system that interrelates pituitary function, reproductive behavior, and chirping.
