Behavioral Alterations in Male Zebrafish After Administration of Androgen Receptor Blockers and an Activator

Androgen receptor (AR) signaling is crucial for mediating male-typical behaviors across vertebrates. Enzalutamide (ENZ) and apalutamide (APA) are two second-generation androgen receptor inhibitors (SGARIs) that have been primarily used in the treatment of prostate cancer. However, these drugs still possess side effects, and there remains limited information regarding their behavioral and neurophysiological impacts following chronic exposure in non-mammalian animal models, particularly in fish. Thus, this study aimed to evaluate the behavioral alterations in adult male zebrafish (Danio rerio) following exposure to specific AR blockers (ENZ and APA) and an activator, dihydrotestosterone (DHT), to provide a comprehensive comparison between each tested drug. Adult male zebrafish were exposed via aqueous immersion to each compound at a 1 ppm concentration for ~2 weeks and were subjected to a battery of behavioral tests. From the results, both AR blockers were found to slightly compromise fish locomotion, with contrary results observed in DHT-treated fish, which displayed an increased locomotor activity together with slight alterations in fish exploratory behaviors. Furthermore, ENZ also caused a tightened shoal formation in zebrafish, while exposure to APA was observed to slightly diminish the fear response of fish. On the other hand, the DHT-treated group displayed a higher level of aggression compared to the vehicle control group. In conclusion, functional modulation of androgen receptor signaling leads to significant alterations in male zebrafish behavior, particularly affecting fear responses, aggression, and anxiety-related behaviors. We believe that these findings could contribute to a deeper understanding of the relationship between androgens and behaviors in vertebrates, especially zebrafish.