Optimization of anesthetic procedure in crustaceans: Evidence for sedative and analgesic-like effect of MS-222 using a semi-automated device for exposure to noxious stimulus

by Selleckchem | Feb 02 2024

The implementation of anesthetic procedure in aquatic crustaceans remains mostly limited to studies dealing with sedation and survival from anesthesia, possibly owing to the debated question of pain in invertebrates. However, two important issues are generally overlooked: actual analgesic-like effect, and possible physiological post-anesthesial effects. Here we report on the anesthetic properties and possible after-effects of MS-222 (Tricaine Methanesulfonate or Ethyl 3-aminobenzoate methanesulfonate) and Eugenol in the freshwater amphipod Gammarus pulex. We first optimized the concentration of MS-222, and the induction and recovery time, based on preliminary tests and published studies. We then relied on the nociceptive modulation of sheltering behavior to assess the analgesic-like effect of the two drugs, using a new semi-automated electric shock device. In addition, we monitored the impact of anesthesia with MS-222 on locomotor activity and oxygen consumption and addressed potential adverse effects upon recovery using biomarkers related to metabolism and neurotoxicity. We provide evidence for the sedative and analgesic-like effects of MS-222 at 600 mg.L-1 and, to a lesser extent, of Eugenol at 100 µL.L-1, with no decrease in survival rate at 6 days post anesthesia. Oxygen consumption was reduced -but not eliminated- under full anesthesia with 600 mg.L-1 MS-222. No significant physiological effect of anesthesia was evidenced on the activity of the mitochondrial electron transfer system, or that of acetylcholine esterase, nor on total antioxidant capacity. We therefore conclude to the efficiency of MS-222 as an anesthetic drug in G. pulex. Eugenol should be tested at a higher concentration to reach the same efficiency, providing that increased concentration would not incur side-effects. Furthermore, the new and original semi-automated electric chock device used to induce nociception can be easily adapted to any species of aquatic invertebrates and small-sized fish and tadpoles, offering a standardized and flexible protocol to study nociceptive response and anesthesia in aquatic organisms.

Comments:

This study on the anesthetic properties of MS-222 and Eugenol in Gammarus pulex seems comprehensive and important for understanding the effects of these compounds on aquatic crustaceans. The optimization of the concentration of MS-222 and the assessment of its induction and recovery times are crucial for effective and humane anesthesia in these organisms.

The utilization of sheltering behavior as a means to assess analgesic-like effects is a clever approach, especially when coupled with a semi-automated electric shock device. This method allows for a standardized way to measure nociceptive responses and evaluate the effectiveness of different anesthetic agents.

The findings regarding the sedative and analgesic-like effects of MS-222 at 600 mg.L-1, as well as the partial effects of Eugenol at 100 µL.L-1, without a decrease in survival rate at 6 days post-anesthesia, are significant. The study's attention to physiological effects, such as reduced oxygen consumption under anesthesia, is also noteworthy.

The absence of significant physiological effects on certain biomarkers related to metabolism and neurotoxicity post-anesthesia provides valuable insights into the safety profile of MS-222 in G. pulex. Additionally, the discussion about potentially testing higher concentrations of Eugenol while considering possible side effects is a prudent direction for future research.

The adaptation of the semi-automated electric shock device for studying nociception in various aquatic invertebrates and small-sized fish and tadpoles is a promising contribution that could standardize research protocols in this field.

Overall, this study not only emphasizes the efficacy of MS-222 as an anesthetic drug in G. pulex but also introduces a novel approach to studying nociceptive responses and anesthesia in aquatic organisms. It opens avenues for further investigation into anesthetic procedures and pain modulation in these species.