Tricaine Methanesulfonate (MS222) Has Short-Term Effects on Young Adult Zebrafish (Danio rerio) Working Memory and Cognitive Flexibility, but Not on Aging Fish

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

The purpose of this study was to characterize the activity of essential oils from Nepeta Cataria (EON) at concentrations of 125 μ L  L-1, 150 μ L  L-1, 175 μ L  L-1, and 200 μ L  L-1 on the behavior of loss of the posture reflex and recovery of the posture reflex and electrocardiographic activity and recording of the opercular beat of Colossoma macropomum during immersion bathing for a period of 5 min, in order to obtain a window for safe use during anesthesia. The fish (23.38 ± 3.5 g) were assigned to the following experiments: experiment 1 (latency to loss and recovery of the posture reflex): (a) 125 μ L  L-1, (b) 150 μ L  L-1, (c) 175 μ L  L-1, and (d) 200 μ L  L-1 (n = 9) per group. Experiment 2 (electrocardiographic and heartbeat recordings): (a) control group; (b) vehicle control group (2 ml of alcohol per liter of water), (c) 125 μ L  L-1, (d) 150 μ L  L-1, (e) 175 μ L  L-1, and (f) 200 μ L  L-1 (n = 9), per group. All the concentrations used showed efficacy in inducing loss of the posture reflex and reversibility with recovery of the posture reflex, but the electrocardiographic recordings indicated morphographic changes such as bradycardia during induction and p wave apiculation during recovery at the highest concentrations tested. In this way, we suggest a safe use window for short-term anesthesia with EON in the concentration range of 125 to 150 μ L  L-1 for juvenile Colossoma macropomum.

Comparison of Tricaine Methanesulfonate (MS-222) and Alfaxalone Anesthesia in Zebrafish (Danio rerio)

The research use of zebrafish has risen exponentially over the past decade while anesthetic options have remained largely unchanged.6 ricaine methanesulfonate (MS-222) is widely accepted as an anesthetic for routine husbandry procedures, however it has limitations and safety concerns. 11 A greater variety of effective anesthetic options for surgical procedures would be advantageous for the research community. Adult zebrafish were randomly assigned to one of the following groups (n = 10, 5 males and 5 females): 200 mg/L MS-222; 6-, 10-, 13-, and 16-mg/L alfaxalone, and control. All zebrafish in the MS-222 group reached a surgical plane of anesthesia within 95 ± 32 s. By contrast, only 2 of 10, 1 of 10, 0 of 10, and 0 of 4 of the 6, 10, 13, and 16 mg/L alfaxalone groups, respectively, reached a surgical plane of anesthesia within the allotted 10-min period. Recovery time was also significantly slower in the alfaxalone groups as compared with MS-222, with some fish taking greater than 10 min to recover. In addition, 33 of 34 zebrafish (the 16 mg/L group was not completed due to safety concerns) in the alfaxalone groups lost opercular movements for greater than one minute during their anesthetic event and had to be removed to the recovery tank. The results demonstrated that alfaxalone was unable to provide a reliable and safe surgical plane of anesthesia at any of the drug doses tested. Therefore, we recommend alfaxalone not be used as an anesthetic for painful procedures on zebrafish and conclude that MS-222 remains a more viable anesthetic for immersion anesthesia in zebrafish.

The Use of Tricaine Methanesulfonate (MS-222) in Asian Seabass (Lates calcarifer) at Different Temperatures: Study of Optimal Doses, Minimum Effective Concentration, Blood Biochemistry, Immersion Pharmacokinetics, and Tissue Distributions

This study was conducted to determine the optimal doses and minimum effective concentrations (MECs) of tricaine methanesulfonate (MS-222) in marketable-size Asian seabass reared at two temperatures (22 and 28 °C). Serum biochemical parameters, pharmacokinetics, and tissue distributions of MS-222 following immersion at the determined optimal doses were also evaluated in order to delineate possible mechanisms dictating the temperature difference. The definition of optimal dose is set as the dose when fish attain stage III anesthesia within 5 min, sustain this stage for 3 min, and re-attain equilibrium within 5 min. The MEC is the fish serum MS-222 concentration when stage III anesthesia is reached. The results showed that water temperature exerted no or minimal impact on the designated parameters. The optimal doses at 22 and 28 °C were 140 and 150 µg/mL, while the MECs were 70.48 and 78.27 µg/mL, respectively. Fish exposed to the optimal doses of MS-222 had significantly elevated blood concentrations of lactate, glucose, calcium, magnesium, and sodium, while the blood pH was significantly decreased. The fish eliminated MS-222 faster at 28 °C than at 22 °C, with serum half-lives of 18.43 and 37.01 h, respectively. Tissue-specific distribution patterns were evident. Irrespective of water temperature, MS-222 peaked at 5 min for the brain and gill but peaked slightly later at 10-20 min for the liver and kidney. Most tissues exhibit a gradual decline of drug concentration except for the gill, which was maintained at a steady level. Muscle is the least perfused tissue with the lowest drug concentration throughout the 90 min period. This study provided physiological and pharmacokinetic evidence contributing to a better understanding of the actions of MS-222 in Asian seabass at different temperatures.

Treatment of Pain in Fish

This chapter provides an overview of our current understanding of clinical analgesic use in fish. Recently, the efficacy and pharmacokinetics of several analgesic drugs for use in fish have been investigated, and the most important data indicates that μ-opioid agonist drugs (e.g, morphine) are consistently effective as analgesics across fish species. In addition, bath application of some analgesic drugs may be useful, which affords multiple methods for delivering analgesics to fish. Although few published studies of non-steroidal anti-inflammatory drugs administered to fish show promise, we have much to learn about the analgesic efficacy of most drugs in this class.

Behavioural Aversion and Cortisol Level Assessment When Adult Zebrafish Are Exposed to Different Anaesthetics

The use of zebrafish (Danio rerio) as an animal model is growing and occurs in a wide range of scientific areas. Therefore, researchers need better and more appropriate anaesthetics for stressful and/or painful procedures to prevent unpleasant experiences. Thus, we aimed to study if adult zebrafish displayed aversion-associated behaviours (conditioned place aversion) and alterations in cortisol levels when exposed to equipotent concentrations of MS222, propofol/lidocaine, clove oil, or etomidate. Adult AB zebrafish (mixed-sex, N = 177) were randomly assigned to MS222 (150 mg/L), Propofol/Lidocaine (5 mg/L propofol + 150 mg/L lidocaine), Clove Oil (45 mg/L), or Etomidate (2 mg/L) groups. The conditioned place aversion test was used to assess behavioural aversion. Only etomidate resulted in a similar aversion to the positive control group (HCl; pH = 3). Cortisol levels were measured 5 and 15 min after loss of equilibrium. Etomidate induced low levels of cortisol by impairing its synthesis, whereas all the other groups had similar cortisol levels. Based on our data, etomidate was ruled out as an alternative to MS222, as it showed an aversive profile. The remaining protocols were not innocuous, displaying a weak aversive profile when compared to the positive control. In conclusion, a combination of propofol with lidocaine, clove oil, and MS222 were valid candidates for use as anaesthetic protocols.