The role of ligand-gated chloride channels in behavioural alterations at elevated CO2 in a cephalopod

Thomas, Jodi T., Spady, Blake L., Munday, Philip L., and Watson, Sue-Ann (2021) The role of ligand-gated chloride channels in behavioural alterations at elevated CO2 in a cephalopod. Journal of Experimental Biology, 224 (13). jeb242335.

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Abstract

Projected future carbon dioxide (CO2) levels in the ocean can alter marine animal behaviours. Disrupted functioning of γ-aminobutyric acid type A (GABAA) receptors (ligand-gated chloride channels) is suggested to underlie CO2-induced behavioural changes in fish. However, the mechanisms underlying behavioural changes in marine invertebrates are poorly understood. We pharmacologically tested the role of GABA-, glutamate-, acetylcholine- and dopamine-gated chloride channels in CO2-induced behavioural changes in a cephalopod, the two-toned pygmy squid (Idiosepius pygmaeus). We exposed squid to ambient (~450 μatm) or elevated (~1000 μatm) CO2 for 7 days. Squid were treated with sham, the GABAA receptor antagonist gabazine or the non-specific GABAA receptor antagonist picrotoxin, before measurement of conspecific-directed behaviours and activity levels upon mirror exposure. Elevated CO2 increased conspecific-directed attraction and aggression, as well as activity levels. For some CO2-affected behaviours, both gabazine and picrotoxin had a different effect at elevated compared with ambient CO2, providing robust support for the GABA hypothesis within cephalopods. In another behavioural trait, picrotoxin but not gabazine had a different effect in elevated compared with ambient CO2, providing the first pharmacological evidence, in fish and marine invertebrates, for altered functioning of ligand-gated chloride channels, other than the GABAAR, underlying CO2-induced behavioural changes. For some other behaviours, both gabazine and picrotoxin had a similar effect in elevated and ambient CO2, suggesting altered function of ligand-gated chloride channels was not responsible for these CO2-induced changes. Multiple mechanisms may be involved, which could explain the variability in the CO2 and drug treatment effects across behaviours.

Item ID: 70284
Item Type: Article (Research - C1)
ISSN: 1477-9145
Keywords: GABA, Gabazine, Ligand-gated chloride channels, Ocean acidification, Picrotoxin, Squid
Copyright Information: © 2021. Published by The Company of Biologists Ltd
Funders: Australian Research Council Centre of Excellence for Coral Reef Studies (ARC CECRS)
Research Data: https://doi.org/10.25903/y6kz-hm11
Date Deposited: 08 Nov 2021 22:38
FoR Codes: 31 BIOLOGICAL SCIENCES > 3109 Zoology > 310906 Animal neurobiology @ 50%
31 BIOLOGICAL SCIENCES > 3109 Zoology > 310913 Invertebrate biology @ 25%
31 BIOLOGICAL SCIENCES > 3199 Other biological sciences > 319902 Global change biology @ 25%
SEO Codes: 18 ENVIRONMENTAL MANAGEMENT > 1802 Coastal and estuarine systems and management > 180203 Coastal or estuarine biodiversity @ 30%
19 ENVIRONMENTAL POLICY, CLIMATE CHANGE AND NATURAL HAZARDS > 1905 Understanding climate change > 190504 Effects of climate change on Australia (excl. social impacts) @ 35%
19 ENVIRONMENTAL POLICY, CLIMATE CHANGE AND NATURAL HAZARDS > 1905 Understanding climate change > 190507 Global effects of climate change (excl. Australia, New Zealand, Antarctica and the South Pacific) (excl. social impacts) @ 35%
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