Sedative effect of 2-phenoxyethanol and essential oil of Lippia alba on stress response in gilthead sea bream (Sparus aurata)

• Essential oil of Lippia alba (EOLA) was tested as anesthetic in Sparus aurata.
• Concentration below 50 and 100–300 μL L− 1 produced sedation and anesthesia, respectively.
• Stress parameters were measured in S. aurata after 4 h of exposure to anesthetics.
• The anesthetic 2-phenoxyethanol prevented a stress response in S. aurata.

The anesthetic efficacy of the essential oil of Lippia alba (EOLA) in Sparus aurata was evaluated by induction and recovery times of anesthesia. After, specimens were exposed to anesthetics low concentrations for 4 h, under nonstress or stress conditions. Range 100–300 μL L− 1 EOLA induced anesthesia. Plasmatic cortisol, glucose, lactate, and osmolality enhanced after EOLA exposure in the undisturbed (UF) and stressed fish (SF). Lower corticotropin-releasing hormone binding-protein expression occurred in SF/EOLA compared with 2-PHE/stress combination or to EOLA/undisturbed conditions. Stress processes reduced prolactin (PRL) expression in the control fish, while UF exhibited reduced PRL levels after exposure to both anesthetics. Proopiomelanocortin (POMCa) mRNA was higher after 2-PHE exposure in SF compared to control; POMCb expression was higher in SF/EOLA in contrast to control and UF/EOLA conditions. Thus, EOLA was an effective anesthetic, but it was unable to prevent a stress response in S. aurata; while 2-PHE is advisable to sedate S. aurata without causing stress, but it was not effective at preventing a stress response in the present work.