Androgen-induced neural plasticity and the regulation of electric-social behavior in the brown ghost knifefish: current status and future directions

Abstract

The weakly electric brown ghost knifefish (Apteronotus leptorhynchus) modulates its electric organ discharge to produce intraspecific communication signals called “chirps”. Although males and females are known to produce chirps during courtship and spawning, they show clear sex differences in their propensity to chirp in response to artificial electrosensory stimuli; males consistently chirp, whereas females generally do not. This species also shows prominent sex differences in substance P-like immunoreactivity (SPl-ir) in brain. Males, but not females, have intense SPl-ir in a number of forebrain regions known to control reproductive functions, including the prepacemaker nucleus (PPn), the command center for chirping behavior. However, androgen treatment enhances both chirping behavior and brain SPl-ir in females. In addition, chirps produced by androgen-treated females are similar to those reported to occur during spawning. The results suggest that steroid-induced neural plasticity of SPl input to the PPn may play an important role in modulating female chirping activity. However, potential problems with this interpretation are discussed.