{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,11,6]],"date-time":"2026-11-06T13:35:03Z","timestamp":1793972103076,"version":"4.8.0"},"reference-count":60,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2021,11,4]],"date-time":"2021-11-04T00:00:00Z","timestamp":1635984000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Biology"],"abstract":"<jats:p>Zebrafish are often euthanized by overdose of anaesthesia. However, fish may have aversion towards some anaesthetics, and protocol efficacy varies between species. Using wild type adult Danio rerio, we assessed time to loss of opercular beat, righting, and startle reflexes during induction of anaesthetic overdose by either tricaine (0.5 g\/L or 1 g\/L), benzocaine (1 g\/L), 2-phenoxyethanol (3 mL\/L), clove oil (0.1%), isoeugenol (540 mg\/L), lidocaine hydrochloride (1 g\/L), or etomidate (50 mg\/L). Initial screening demonstrated that benzocaine and buffered lidocaine hydrochloride achieved the fastest loss of reflexes. The rapid induction times were confirmed when retesting using larger batches of fish. The fastest induction was obtained with 1 g\/L lidocaine hydrochloride buffered with 2 g\/L NaHCO3, in which all adult zebrafish lost reflexes in less than 2 min. Next, we monitored signs of distress during benzocaine or buffered lidocaine hydrochloride overdose induction. The results indicated that buffered lidocaine hydrochloride caused significantly less aversive behaviors than benzocaine. Finally, we tested several buffers to refine the lidocaine hydrochloride immersion. The most efficient buffer for euthanasia induction using 1g\/L lidocaine hydrochloride was 2 g\/L NaHCO3 with 50 mL\/L 96% ethanol, inducing immobility in less than 10 s and with only 2% of adult zebrafish displaying aversive behaviors during treatment.<\/jats:p>","DOI":"10.3390\/biology10111133","type":"journal-article","created":{"date-parts":[[2021,11,4]],"date-time":"2021-11-04T09:11:32Z","timestamp":1636017092000},"page":"1133","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":27,"title":["Screening of Anaesthetics in Adult Zebrafish (Danio rerio) for the Induction of Euthanasia by Overdose"],"prefix":"10.3390","volume":"10","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4886-9699","authenticated-orcid":false,"given":"Kristine","family":"von Krogh","sequence":"first","affiliation":[{"name":"von Krogh Consult, 1266 Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Joseph","family":"Higgins","sequence":"additional","affiliation":[{"name":"The Francis Crick Institute, London NW1 1AT, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yolanda","family":"Saavedra Torres","sequence":"additional","affiliation":[{"name":"The Francis Crick Institute, London NW1 1AT, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4895-6867","authenticated-orcid":false,"given":"Jean-Philippe","family":"Mocho","sequence":"additional","affiliation":[{"name":"Joint Production System Ltd., Potters Bar EN6 3DD, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,11,4]]},"reference":[{"key":"ref_1","unstructured":"European Union (2010). Directive 2010\/63\/EU of the European Parliament and of the Council; On the protection of animals used for scientific purposes. Off. J. Eur. Union, 276, 33\u201379."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1664","DOI":"10.1089\/neu.2013.3243","article-title":"Anesthesia for Euthanasia Influences mRNA Expression in Healthy Mice and after Traumatic Brain Injury","volume":"31","author":"Kriege","year":"2014","journal-title":"J. Neurotrauma"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"560","DOI":"10.1080\/15222055.2012.691013","article-title":"Efficacy and Physiological Responses of Grass Carp to Different Sedation Techniques: I. Effects of Various Chemicals on Sedation and Blood Chemistry","volume":"74","author":"Gause","year":"2012","journal-title":"N. Am. J. Aquac."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"296","DOI":"10.1080\/19425120.2017.1321593","article-title":"Efficacy and Physiological Response to Chemical Anesthesia in Wild Hickory Shad during Spawning Season","volume":"9","author":"Matsche","year":"2017","journal-title":"Mar. Coast. Fish."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"510","DOI":"10.1089\/zeb.2012.0854","article-title":"Mapping of Zebrafish Research: A Global Outlook","volume":"10","author":"Kinth","year":"2013","journal-title":"Zebrafish"},{"key":"ref_6","unstructured":"European Commission (2020). 2019 Report on the Statistics on the Use of Animals for Scientific Purposes in the Member States of the European Union in 2015\u20132017, European Commission. Report from the commission to the European parliament and the council; Report no. COM(2020) 16 final."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1891","DOI":"10.1111\/jfb.13278","article-title":"International survey on the use and welfare of zebrafish Danio rerio in research","volume":"90","author":"Lidster","year":"2017","journal-title":"J. Fish Biol."},{"key":"ref_8","first-page":"785","article-title":"Evaluation of Rapid Cooling and Tricaine Methanesulfonate (MS222) as Methods of Euthanasia in Zebrafish (Danio rerio)","volume":"48","author":"Wilson","year":"2009","journal-title":"J. Am. Assoc. Lab. Anim. Sci."},{"key":"ref_9","first-page":"816","article-title":"Lidocaine Hydrochloride Compared with MS222 for the Euthanasia of Zebrafish (Danio rerio)","volume":"55","author":"Collymore","year":"2016","journal-title":"J. Am. Assoc. Lab. Anim. Sci."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"109","DOI":"10.3109\/07420528.2010.538105","article-title":"Daily Rhythms of Toxicity and Effectiveness of Anesthetics (MS222 and Eugenol) in Zebrafish (Danio Rerio)","volume":"28","author":"Terry","year":"2011","journal-title":"Chronobiol. Int."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Wong, D., Von Keyserlingk, M.A.G., Richards, J.G., and Weary, D.M. (2014). Conditioned Place Avoidance of Zebrafish (Danio rerio) to Three Chemicals Used for Euthanasia and Anaesthesia. PLoS ONE, 9.","DOI":"10.1371\/journal.pone.0088030"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Readman, G.D., Owen, S., Murrell, J.C., and Knowles, T. (2013). Do Fish Perceive Anaesthetics as Aversive?. PLoS ONE, 8.","DOI":"10.1371\/journal.pone.0073773"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"317","DOI":"10.1177\/0023677221998403","article-title":"Anaesthesia of laboratory, aquaculture and ornamental fish: Proceedings of the first LASA-FVS Symposium","volume":"55","author":"Schroeder","year":"2021","journal-title":"Lab. Anim."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"343","DOI":"10.1093\/ilar.50.4.343","article-title":"Fish Sedation, Anesthesia, Analgesia, and Euthanasia: Considerations, Methods, and Types of Drugs","volume":"50","author":"Neiffer","year":"2009","journal-title":"ILAR J."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1038\/s41598-017-06917-2","article-title":"Species specific anaesthetics for fish anaesthesia and euthanasia","volume":"7","author":"Readman","year":"2017","journal-title":"Sci. Rep."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"19","DOI":"10.12717\/DR.2017.21.1.019","article-title":"Effects of Clove Oil and Lidocaine-HCl Anesthesia on Water Parameter during Simulated Transportation in the Marine Medaka, Oryzias dancena","volume":"21","author":"Park","year":"2017","journal-title":"Dev. Reprod."},{"key":"ref_17","first-page":"76","article-title":"Effectiveness of Recommended Euthanasia Methods in Larval Zebrafish (Danio rerio)","volume":"54","author":"Strykowski","year":"2015","journal-title":"J. Am. Assoc. Lab. Anim. Sci."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"192","DOI":"10.1093\/ilar.53.2.192","article-title":"Anesthesia and Euthanasia in Zebrafish","volume":"53","author":"Matthews","year":"2012","journal-title":"ILAR J."},{"key":"ref_19","first-page":"58","article-title":"Effectiveness of Rapid Cooling as a Method of Euthanasia for Young Zebrafish (Danio rerio)","volume":"57","author":"Wallace","year":"2018","journal-title":"J. Am. Assoc. Lab. Anim. Sci."},{"key":"ref_20","first-page":"e55306","article-title":"Environmental Screening of Aeromonas hydrophila, Mycobacterium spp., and Pseudocapillaria tomentosa in Zebrafish Systems","volume":"130","author":"Mocho","year":"2017","journal-title":"J. Vis. Exp."},{"key":"ref_21","first-page":"198","article-title":"Efficacy and Safety of 5 Anesthetics in Adult Zebrafish (Danio rerio)","volume":"53","author":"Collymore","year":"2014","journal-title":"J. Am. Assoc. Lab. Anim. Sci."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"46","DOI":"10.1089\/154585404774101671","article-title":"The Efficacy of Clove Oil As An Anesthetic for the Zebrafish, Danio rerio (Hamilton)","volume":"1","author":"Grush","year":"2004","journal-title":"Zebrafish"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"5427","DOI":"10.1113\/JP271794","article-title":"In vivo physiological recording from the lateral line of juvenile zebrafish","volume":"594","author":"Olt","year":"2016","journal-title":"J. Physiol."},{"key":"ref_24","first-page":"1535","article-title":"Anesthesia in fishes","volume":"28","author":"McFarland","year":"1969","journal-title":"Fed. Proc."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1258\/002367797780600297","article-title":"Recommendations for euthanasia of experimental animals: Part 2","volume":"31","author":"Close","year":"1997","journal-title":"Lab. Anim."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"17541","DOI":"10.1038\/s41598-018-36130-8","article-title":"Recordings in an integrating central neuron provide a quick way for identifying appropriate anaesthetic use in fish","volume":"8","author":"Machnik","year":"2018","journal-title":"Sci. Rep."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"395","DOI":"10.1016\/0044-8486(84)90207-2","article-title":"The use of lidocaine-sodium bicarbonate as anaesthetic in fish","volume":"41","author":"Carrasco","year":"1984","journal-title":"Aquaculture"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"20190290","DOI":"10.1098\/rstb.2019.0290","article-title":"Evolution of nociception and pain: Evidence from fish models","volume":"374","author":"Sneddon","year":"2019","journal-title":"Philos. Trans. R. Soc. B Biol. Sci."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"457","DOI":"10.1080\/01621459.1958.10501452","article-title":"Nonparametric Estimation from Incomplete Observations","volume":"53","author":"Kaplan","year":"1958","journal-title":"J. Am. Stat. Assoc."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"331","DOI":"10.1016\/j.otohns.2010.05.007","article-title":"A practical guide to understanding Kaplan-Meier curves","volume":"143","author":"Rich","year":"2010","journal-title":"Otolaryngol. Neck Surg."},{"key":"ref_31","first-page":"163","article-title":"Evaluation of survival data and two new rank order statistics arising in its consideration","volume":"50","author":"Mantel","year":"1966","journal-title":"Cancer Chemother. Rep."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"185","DOI":"10.2307\/2344317","article-title":"Asymptotically Efficient Rank Invariant Test Procedures","volume":"135","author":"Peto","year":"1972","journal-title":"J. R. Stat. Soc. Ser. A"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Armitage, P., and Colton, T. (2005). Linear Rank Tests in Survival Analysis. Encyclopedia of Biostatistics, Wiley.","DOI":"10.1002\/0470011815"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"80","DOI":"10.2307\/3001968","article-title":"Individual Comparisons by Ranking Methods","volume":"1","author":"Wilcoxon","year":"1945","journal-title":"Biom. Bull."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"50","DOI":"10.1214\/aoms\/1177730491","article-title":"On a Test of Whether one of Two Random Variables is Stochastically Larger than the Other","volume":"18","author":"Mann","year":"1947","journal-title":"Ann. Math. Stat."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"143","DOI":"10.11613\/BM.2013.018","article-title":"The Chi-square test of independence","volume":"23","author":"McHugh","year":"2013","journal-title":"Biochem. Med."},{"key":"ref_37","first-page":"131","article-title":"A Survey of Exact Inference for Contingency Tables: Rejoinder","volume":"7","author":"Agresti","year":"1992","journal-title":"Stat. Sci."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"583","DOI":"10.1080\/01621459.1952.10483441","article-title":"Use of Ranks in One-Criterion Variance Analysis","volume":"47","author":"Kruskal","year":"1952","journal-title":"J. Am. Stat. Assoc."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"52","DOI":"10.1080\/01621459.1961.10482090","article-title":"Multiple Comparisons among Means","volume":"56","author":"Dunn","year":"1961","journal-title":"J. Am. Stat. Assoc."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"330","DOI":"10.1089\/zeb.2021.0023","article-title":"Adult Zebrafish Anesthesia: A Study of Efficacy and Behavioral Recovery of Different Anesthetics","volume":"18","author":"Jorge","year":"2021","journal-title":"Zebrafish"},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Valentim, A., F\u00e9lix, L., Carvalho, L., Diniz, E., and Antunes, L. (2016). A New Anaesthetic Protocol for Adult Zebrafish (Danio rerio): Propofol Combined with Lidocaine. PLoS ONE, 11.","DOI":"10.1371\/journal.pone.0147747"},{"key":"ref_42","doi-asserted-by":"crossref","unstructured":"Nordgreen, J., Tahamtani, F.M., Janczak, A.M., and Horsberg, T.E. (2014). Behavioural Effects of the Commonly Used Fish Anaesthetic Tricaine Methanesulfonate (MS-222) on Zebrafish (Danio rerio) and Its Relevance for the Acetic Acid Pain Test. PLoS ONE, 9.","DOI":"10.1371\/journal.pone.0092116"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"451","DOI":"10.1089\/zeb.2019.1737","article-title":"Clove Oil and AQUI-S Efficacy for Zebrafish Embryo, Larva, and Adult Anesthesia","volume":"16","author":"Ehrlich","year":"2019","journal-title":"Zebrafish"},{"key":"ref_44","first-page":"564","article-title":"Effects of Clove Oil as a Euthanasia Agent on Blood Collection Efficiency and Serum Cortisol Levels in Danio rerio","volume":"54","author":"Davis","year":"2015","journal-title":"J. Am. Assoc. Lab. Anim. Sci."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"732","DOI":"10.30802\/AALAS-JAALAS-20-000027","article-title":"A Comparison of Buffered Tricaine Methanesulfonate (MS-222) and Isoeugenol Anesthesia for Caudal Fin Clipping in Zebrafish (Danio rerio)","volume":"59","author":"Musk","year":"2020","journal-title":"J. Am. Assoc. Lab. Anim. Sci."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1016\/j.applanim.2016.12.003","article-title":"Exploring the efficacy of immersion analgesics in zebrafish using an integrative approach","volume":"187","author":"Schroeder","year":"2017","journal-title":"Appl. Anim. Behav. Sci."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"297","DOI":"10.1089\/zeb.2010.0653","article-title":"Combined Use of MS-222 (Tricaine) and Isoflurane Extends Anesthesia Time and Minimizes Cardiac Rhythm Side Effects in Adult Zebrafish","volume":"7","author":"Huang","year":"2010","journal-title":"Zebrafish"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"1582","DOI":"10.1111\/are.12308","article-title":"The efficacy of MS-222 as anaesthetic agent in four freshwater aquarium fish species","volume":"46","author":"Chambel","year":"2013","journal-title":"Aquac. Res."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"71","DOI":"10.1089\/zeb.2012.0858","article-title":"The Evaluation of Rapid Cooling as an Anesthetic Method for the Zebrafish","volume":"11","author":"Chen","year":"2014","journal-title":"Zebrafish"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"337","DOI":"10.1577\/1548-8659(1982)111<337:E>2.0.CO;2","article-title":"Etomidate: Effective Dosages for a New Fish Anesthetic","volume":"111","author":"Amend","year":"1982","journal-title":"Trans. Am. Fish. Soc."},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Martins, T., Diniz, E., F\u00e9lix, L.M., and Antunes, L. (2018). Evaluation of anaesthetic protocols for laboratory adult zebrafish (Danio rerio). PLoS ONE, 13.","DOI":"10.1371\/journal.pone.0197846"},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"476","DOI":"10.1177\/0023677216670686","article-title":"Anaesthesia and analgesia in laboratory adult zebrafish: A question of refinement","volume":"50","author":"Martins","year":"2016","journal-title":"Lab. Anim."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"32","DOI":"10.1053\/j.jepm.2011.11.009","article-title":"Clinical Anesthesia and Analgesia in Fish","volume":"21","author":"Sneddon","year":"2012","journal-title":"J. Exot. Pet Med."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"719","DOI":"10.1007\/s10695-009-9346-2","article-title":"Anesthesia induces stress in Atlantic salmon (Salmo salar), Atlantic cod (Gadus morhua) and Atlantic halibut (Hippoglossus hippoglossus)","volume":"36","author":"Zahl","year":"2010","journal-title":"Fish Physiol. Biochem."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"2571","DOI":"10.1111\/j.1095-8649.2010.02633.x","article-title":"Humane killing of fishes for scientific research: A comparison of two methods","volume":"76","author":"Blessing","year":"2010","journal-title":"J. Fish Biol."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"94","DOI":"10.1016\/j.applanim.2017.10.014","article-title":"Physiological and behavioural evaluation of common anaesthesia practices in the rainbow trout","volume":"199","author":"Pounder","year":"2018","journal-title":"Appl. Anim. Behav. Sci."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"1942","DOI":"10.1021\/mp2006467","article-title":"Ethanol Effects on Apparent Solubility of Poorly Soluble Drugs in Simulated Intestinal Fluid","volume":"9","author":"Fagerberg","year":"2012","journal-title":"Mol. Pharm."},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"137","DOI":"10.1016\/j.pbb.2013.03.013","article-title":"iPhone\u00ae applications as versatile video tracking tools to analyze behavior in zebrafish (Danio rerio)","volume":"106","author":"Pittman","year":"2013","journal-title":"Pharmacol. Biochem. Behav."},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"174","DOI":"10.1016\/j.physbeh.2013.10.023","article-title":"Startle response memory and hippocampal changes in adult zebrafish pharmacologically-induced to exhibit anxiety\/depression-like behaviors","volume":"123","author":"Pittman","year":"2014","journal-title":"Physiol. Behav."},{"key":"ref_60","doi-asserted-by":"crossref","first-page":"128","DOI":"10.1016\/j.bbr.2010.10.015","article-title":"Preference for ethanol in zebrafish following a single exposure","volume":"217","author":"Mathur","year":"2011","journal-title":"Behav. Brain Res."}],"container-title":["Biology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2079-7737\/10\/11\/1133\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T07:25:50Z","timestamp":1760167550000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2079-7737\/10\/11\/1133"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,11,4]]},"references-count":60,"journal-issue":{"issue":"11","published-online":{"date-parts":[[2021,11]]}},"alternative-id":["biology10111133"],"URL":"https:\/\/doi.org\/10.3390\/biology10111133","relation":{},"ISSN":["2079-7737"],"issn-type":[{"value":"2079-7737","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,11,4]]}}}