Many fish species perform alarm reactions when exposed to olfactory cues from injured conspecifics. In the crucian carp this response includes characteristic components of avoidance behaviour such as escape and freezing. The peripheral parts of the olfactory system implicated in the alarm reaction have been described, but the central mechanisms involved are largely unknown. Corticotrophin-releasing factor (CRF) is central in the mediation of behavioural and physiological reactions to fear and stress, but its role in non-mammalian vertebrates needs further investigation. The involvement of CRF in the crucian carp alarm reaction was studied by intraperitoneal injections of the non-peptidergic CRF₁ antagonist antalarmin. One hour after injection, the fish were exposed to skin extract from conspecifics. The treatment resulted in an inhibition of both escape and freezing behaviour, while vehicle treated individuals displayed fully expressed alarm reactions. These observations suggest that the CRF₁ receptor is involved in the crucian carp alarm reaction, and give support to the idea that CRF might be a component in fear induced behaviour among vertebrates.

Supported by the Norwegian Research Council