Exposure to menthol is expected to alleviate physiological and oxidative stress in fish. Yet, its effects as an anesthetic-like compound on the heart function and associated physiological and biochemical changes still need further clarification. This study aimed to analyze the effects of menthol on the cardiac function and oxidative stress responses of Colossoma macropomum exposed to short-term baths. Fish were divided into three groups: control, menthol-exposed fish (40, 60 and 80 mg L⁻¹) and fish in recovery. The electrocardiogram (ECG) tracing patterns, wave intervals (RR; QT), complex duration (QRS) and heart rate were assessed after 5 min recordings throughout exposure and recovery. Total antioxidant capacity against peroxyl radicals (ACAP), glutathione S-transferase (GST) activity and lipoperoxidation (LPO) levels were also evaluated in the heart tissue. All concentrations of menthol depressed the heart rate and prolonged RR and QT intervals in a concentration-dependent fashion. QRS complex duration was only reduced at the highest dose of menthol. During recovery, heart rate and mean amplitude were still reduced at 60 or 80 mg L⁻¹ menthol, whereas wave intervals were still longer at these concentrations. Notwithstanding, QRS complex resumed its normal duration during recovery. GST activity and ACAP were unchanged in fish exposed to menthol. However, LPO reduced in fish exposed to 40 and 60 mg L⁻¹ menthol. In conclusion, all concentrations of menthol induced anesthesia in C. macropomum without causing mortality, albeit provoking transient cardiac alterations. Menthol at 40 and 60 mg L⁻¹ could be considered suitable concentrations to immobilize fish as they not only did not compromise cardiac function but reduced LPO in the heart. Yet, menthol at 80 mg L⁻¹ or higher doses should be avoided as there is a potential for the emergence of a life-threatening cardiac depression and oxidative stress.

暴露于薄荷醇有望减轻鱼类的生理和氧化应激。然而，其作为麻醉剂样化合物对心脏功能以及相关的生理和生化变化的作用仍需要进一步阐明。这项研究旨在分析薄荷醇对短期洗澡对巨斗兽场的心脏功能和氧化应激反应的影响。将鱼分为三组：对照，薄荷暴露的鱼（40、60和80 mg L ^-1）和恢复中的鱼。在整个暴露和恢复过程中记录5分钟后，评估心电图（ECG）的追踪模式，波间隔（RR; QT），复杂持续时间（QRS）和心率。还评估了心脏组织中抗过氧自由基（ACAP），谷胱甘肽S-转移酶（GST）活性和脂过氧化（LPO）水平的总抗氧化剂能力。所有浓度的薄荷醇均以浓度依赖的方式降低了心率并延长了RR和QT间隔。QRS复合物的持续时间仅在最高剂量的薄荷醇下才减少。在恢复过程中，心率和平均振幅仍在60或80 mg L ^-1时降低薄荷醇，而在这些浓度下波间隔仍更长。尽管如此，QRS复合体在恢复过程中恢复了其正常工期。暴露于薄荷醇的鱼的GST活性和ACAP不变。但是，暴露于40和60 mg L ^-1薄荷醇的鱼的LPO降低。总之，尽管引起短暂的心脏改变，所有浓度的薄荷醇都能在大果梭菌中诱导麻醉，而不会引起死亡。薄荷醇在40和60 mg L ^-1时被认为是固定鱼类的合适浓度，因为它们不仅不会损害心脏功能，而且会降低心脏中的LPO。然而，薄荷醇含量为80 mg L ^-1 否则应避免使用高剂量或高剂量的药物，因为这可能会危及生命，降低心脏的抑郁症和氧化应激。