Abstract
In animal husbandry, livestock industry and research facilities, anaesthetic agents are frequently used to moderate stressful intervention. For mammals and birds, procedures have been established to fine-tune anaesthesia according to the intervention. In ectothermic vertebrates, however, and despite changes in legislation and growing evidence on their cognitive abilities, the presently available information is insufficient to make similarly informed decisions. Here we suggest a straightforward way for rapidly filling this gap. By recording from a command neuron in the brain of fish whose crucial role requires it to integrate and process information from all sensory systems and to relay it to motor output pathways, the specific effects of candidate anaesthesia on central processing of sensory information can directly and efficiently be probed. Our approach allows a rapid and reliable way of deciding if and at which concentration a given anaesthetic affects the central nervous system and sensory processing. We employ our method to four anaesthetics commonly used in fish and demonstrate that our method quickly and with small numbers of animals provides the critical data for informed decisions on anaesthetic use.
Highlights
In many countries, legislation no longer distinguishes between ‘higher’ and ‘lower’ vertebrates, but requires for all vertebrates that anaesthetics are used in all interventions that could be stressful[1,2,3,4,5]
Given the steadily accumulating evidence on higher cognitive functions in fish[13,14,15,16,17,18,19], given that legislation already demands it in a growing number of states and given the time needed for drug companies and legislation to establish new anaesthetics, it is clear that we do not have long time as we took in mammals and birds to establish appropriate data for ectothermic vertebrates that can be used in legal decision making[20,21]
We first applied anaesthetic concentrations commonly used in teleost fish: 0.2 to 0.6 ml L−1 2-PE, 20 to 100 mg L−1 MS-222 and benzocaine and 10 to 20 mg L−1 Aqui-S, respectively[4,21,23,26,27,28,29]
Summary
Legislation no longer distinguishes between ‘higher’ and ‘lower’ vertebrates, but requires for all vertebrates that anaesthetics are used in all interventions that could be stressful[1,2,3,4,5]. For fish and other ectothermic vertebrates, we are presently lacking information about the effects of potential anaesthetic agents on sensory systems and sensory processing This massively limits the possibilities to make similar informed decisions on anaesthesia so that there currently is a serious gap between legislative demands and the data required to fulfil them. The key is that their natural function requires these neurons to integrate information from all sensory systems and to rapidly issue a motor command that would allow the fish to rapidly escape from potential danger (Fig. 1a) We show that this system is ideally suited to determine quickly the effect of a given anaesthetic on various sensory systems, on central processing and motor output. Our findings thereby can be used as a first guide to scientists, veterinarians and aquaculture specialists until further pursuing our approach leads, in the coming years, to a finer picture with more options
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