Effect of isoeugenol sedation on plasma cortisol, glucose, and lactate dynamics in channel catfish Ictalurus punctatus exposed to three stressors

Abstract

The effect of isoeugenol sedation (2.5 mg l −1) on plasma cortisol, glucose, and lactate dynamics in channel catfish ( Ictalurus punctatus), relative to two controls, was examined during confinement, exposure to high unionized ammonia, and acute oxygen depletion. The positive control (PC) for each treatment was no sedation, and the negative control (NC) was sedation with metomidate hydrochloride (1.5 mg l −1). Isoeugenol sedated catfish had 60% lower ( P<0.05) plasma cortisol levels than PC fish after 15-min of confinement. No differences ( P>0.05) in plasma levels of glucose or lactate were observed between treatments during 45-min of confinement. Fish exposed to high ammonia for 24-h had elevated ( P<0.05) cortisol levels in PC and isoeugenol treatment groups. Sedation with isoeugenol during exposure to high ammonia had no effect on plasma glucose or lactate levels relative to PC fish. Levels of plasma cortisol, glucose, and lactate all increased significantly ( P<0.05) in PC fish following acute oxygen depletion for 30 min. Plasma glucose levels were similar ( P>0.05) between isoeugenol and control treated fish throughout oxygen stress and recovery. Sedation with isoeugenol significantly suppressed the resulting plasma cortisol and lactate response by 74% and 46%, respectively, compared to PC fish. Plasma cortisol levels in NC fish were below detection limits for all stress treatments. As a sedative, isoeugenol had suppressive effects on channel catfish plasma cortisol levels during confinement and low oxygen conditions, and reduced the plasma lactate response to acute oxygen depletion.