Figure 7.

Alarm substance-induced fear conditioning and GPR139 agonist treatment timeline during the conditioning. (A) Schematic drawing of conspecific alarm substance (AS)-induced fear conditioning paradigm. Adopted by Sivalingam et al. (2020)³⁰. During pre-conditioning (Day-1), fish was given a choice for their preferred colour, either yellow or white coloured compartment (basal preference). After conditioning to AS-induced fear responses (Day-2), their change in preference was assessed based on their total time spent in AS-paired (originally preferred) compartment as compared to the initial preference (Day-3). (B) On Day-2 (conditioning phase), fish were individually placed into the compartment, and after 5 min of acclimatisation time, AS was delivered in water followed by 5-min of video recording. The fish was then immediately transferred into the non-preferred compartment of the new experimental tank and exposed with 2 mL of distilled water (H₂O) for 5-min. In order to avoid the conditioning to AS-induced fear but not to intraperitoneal-administration and handling stress, GPR139 agonist was then intraperitoneally injected after 60 min of the recovery from the conditioned stimuli (in total 65-min from the fear conditioning), and fish were transferred to their respective home tank.