Abstract
Global warming and connected acidification of the world ocean attract a substantial amount of research efforts, in particular in a context of their impact on behaviour and metabolism of marine organisms, such as Cnidaria. Nevertheless, mechanisms underlying Cnidarians’ neural signalling and behaviour and their (possible) alterations due to the world ocean acidification remain poorly understood. Here we researched for the first time modulation of GABAA receptors (GABAARs) in Actinia equina (Cnidaria: Anthozoa) by pH fluctuations within a range predicted by the world ocean acidification scenarios for the next 80–100 years and by selective pharmacological activation. We found that in line with earlier studies on vertebrates, both changes of pH and activation of GABAARs with a selective allosteric agonist (diazepam) modulate electrical charge transfer through GABAAR and the whole-cell excitability. On top of that, diazepam modifies the animal behavioural reaction on startle response. However, despite behavioural reactions displayed by living animals are controlled by GABAARs, changes of pH do not alter them significantly. Possible mechanisms underlying the species resistance to acidification impact are discussed.
Highlights
The present rise of atmospheric C O2 significantly increases the partial pressure of C O2 in the world oceans and, leads to ocean acidification (OA)
We found that GABA (100 nM) and a specific G ABAAR agonist MSC (1 μM) evoke single-channel openings, whereas GABAAR open channel blocker PTX (20 μM) shuts G ABAAR openings induced by MSC (Fig. 1A)
We demonstrated for the first time the effect of a specific agonist of a GABAAR in Anthozoa at a singlereceptor level and studied the projection of such an effect to modulation of the whole cell excitatory signalling and further to the level of behaviour control
Summary
The present rise of atmospheric C O2 significantly increases the partial pressure of C O2 in the world oceans and, leads to ocean acidification (OA). Different model scenarios predict a decline in pH values of oceanic waters by up to 0.45 units by the year 2100 [7, 39], with profound consequences to marine ecosystems [14]. In this context, the potential impact of OA on coral cnidarians (Cnidaria: Anthozoa, Scleractinia) attracts understandably significant research efforts given the global role of coral reefs and their sensitivity to water pH and connected fluctuations of carbonate–bicarbonate balance. The impact of OA on non-symbiotic sea anemones has yet to be determined
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