Recognizing the opponent: The consolidation of long-term social memory in zebrafish males

Abstract

In male zebrafish, Danio rerio, we observed that there is a memory of an agonistic encounter against a particular opponent, which generates a behavioral modulation in successive encounters. This effect is prevented by treatment with an amnesic agent (MK-801) after the first encounter. Evaluating the neuronal activation through C-fos protein quantification in thelencephalic nuclei, significant differences were found between the fish with social interaction and the control group (isolated fish without interaction), showing greater neuronal activation in the ventral nucleus of the ventral telencephalic region (Vv) when the individuals had social interaction. The same trend was observed in the dorsal nucleus of the ventral region (Vd) and in the medial nucleus of the dorsal region (Dm). In the lateral nucleus of the dorsal telencephalic area (Dl), a greater activation was observed in fish previously exposed to MK-801 (they interact against an opponent of which they would have no memory) than in fish treated with water (they interact with an opponent of which they would have memory). We also found differences in the correlation between nuclei (Vv,Vd,Dm,Dl) for each treatment (water, MK-801 and control group), evaluating not only the activation of each nucleus but also the interaction between them. Finally, we did not observe a clear relationship between the levels of aggressiveness shown by individuals and neuronal activation.