Robledo-Sanchez, K. C. M. | bioRxiv Science

bioRxiv2021

The effect of hydrophobic gases on the nervous system of Daphnia magna

Hundreds of hydrophobic substances: alkanes, alcohols, benzodiacepines, barbiturates, ethers and even gases, can induce General Anaesthesia (GA) in mammal animals. Moreover, it has been suggested that the primary site of action of such agents is on the spinal cord. Here, we investigate a scenario that is in double measure important to understand the mechanisms behind GA: its induction under water in invertebrate animals. We evaluate the capacity of xenon, nitrous oxide and krypton to suppress harmful sensations, provoked by intense light, in the crustacean D. magna. Due to the hydrophobic characteristics of those gases, we designed a special chamber to force them to dissolve in water at pressures up to to 50 atmospheres, whereas at the same time measure in real time the motility of the animals. Surprisingly, the aquatic animals are immobilized with xenon and nitrous oxide. Under this condition, they dont respond to a noxious stimulus. Our results are crucial to understand the action of inert gases in GA and the role of the spinal cord.

neuroscience↗

bioRxiv2021

The effect of hydrophobic gases on the nervous system of Daphnia magna

It is well known that some hydrophobic atomic and molecular gases provoke anaesthetic effects in mammal animals. Depending on the gas, there is a Minimum Alveolar Concentration (MAC) to produce anaesthesia. The gas enters in the lungs, dissolve in the blood and reaches the brain. Where are the targets and which are the action mechanisms are subjects not fully understood yet. Very recently, we reported the effects of local anaesthetics on the swimming behaviour of the water flea Daphnia magna (STOTEN 691, 278-283, 2019). Our aim now is to report new studies on the behaviour of this aquatic invertebrate in the presence of three hydrophobic gases: xenon, nitrous oxide and krypton. However, if local anaesthetics easily dissolve in water, these gases do not. Therefore, we designed a chamber to dissolve the gases using pressures up to 50 atmospheres. Simultaneously, we were able to measure in real time the response of the animals through transparent windows able to support such high pressures. Xenon and nitrous oxide effectively induce lack of movement in the daphnids. The effective pressures EP50 for xenon and nitrous oxide were and 5.2 atmospheres, respectively. Krypton does not present clear effects on the motile suppression, even after the exposure to 44 atmospheres. Our findings provide insight on the physiological effects important gases used in human medicine produce in aquatic invertebrate animals considered as potential models to study anesthesia.

neuroscience↗