Figure 1

Alarm substance-induced fear conditioning and GPR139 antagonist and agonist treatment timeline during the conditioning. (A) Schematic of treatment timeline. After an acclimatization of 1 week, fish were given a choice of their preferred color (Day 1), either a yellow or white colored compartment (basal preference). On Day 2 (conditioning phase), fish were individually placed into the compartment, and after 5 min of acclimatization time, AS was delivered in water, followed by 5 min of video recording. The fish were then immediately transferred into the non-preferred compartment of the new experimental tank and exposed to 2 mL of distilled water (H₂O) for 5 min. Intracranial injection of GPR139 antagonist and intraperitoneal injection of GPR139 agonist were then administered after 60 min of the recovery from the conditioned stimuli, and fish were transferred to their respective home tank. On Day 3 (post-conditioning phase), change in preference was assessed based on their total time spent in AS-paired (originally preferred) compartment as compared to the initial preference. (B) Schematic representation of conspecific alarm substance (AS)-induced fear conditioning paradigm. Adopted by Sivalingam et al. (2020) (Created with BioRender.com).