Electroencephalographic Response in Juvenile Tambaqui, Colossoma macropomum, Exposed to Short-Term Anaesthetic Baths with Geraniol and Citronellol

Abstract

The aim of this study was to evaluate the level of neuronal depression in juvenile tambaqui, Colossoma macropomum, exposed to geraniol (GRL) and citronellol (CTL) in immersion baths. A total of 36 juveniles weighing 35.2 ± 9.4 g were used, organised into six experimental groups: I—control (clean water); II—ethanol (water containing the highest volume of ethanol used in the anaesthetic pre-dilution); III—GRL induction (70 µL·L−1); IV—CTL induction (90 µL·L−1); V—GRL recovery; VI—CTL recovery. Electroencephalographic (EEG) recordings were performed for 300 s in each group. EEG tracings of the control and ethanol groups showed regular and similar activity. Upon exposure to the anaesthetics, irregularities were observed in the tracings showing neuronal excitability and increased amplitudes, mainly in the case of CTL. Overall, GRL-exposed fish showed depression of the central nervous system with low and regular tracings throughout induction, presenting a gradual recovery and stable tracings, which were consistent with an adequate general anaesthetic effect. On the other hand, fish exposed to CTL showed altered EEG activity during induction, that could be considered incompatible with an appropriate anaesthetic effect and smooth recovery, presenting high and irregular EEG tracing amplitudes.

Behavioral and electrophysiological study in Colossoma macropomum treated with different concentrations of Nepeta cataria oil in an immersion bath revealed a therapeutic window for anesthesia

“…However, studies involving electrocardiographic data during induction of anesthesia with agents such as citronellol, geraniol, Piper divaricatum oil, eugenol and lidocaine did not show P wave apiculation (De Araújo et al 2023, Vilhena et al 2022Fujimoto et al 2017;Vieira et al 2023), which may be related to the effect of EON on the heart.…”