Effect of the most commonly utilized ‘anaesthetic’ agents on the isolated heart of the cephalopod mollusk Octopus vulgaris

Using an in vitro isolated and perfused working heart, we analysed cardiac performance of Octopus vulgaris following in vivo exposition of the animals to different formulations and exposure times of anaesthetic agents (based on MgCl2 and its combination with ethanol). Hypothermia (4°C) was used as control (exposure for 5-10’) to discriminate a potential toxic effect of substances. Cardiac performance was evaluated both at basal and stimulated conditions (Frank-Starling response). Among MgCl2 formulations, marked differences in terms of preload sensitivity were observed: the higher increases in stroke volume were revealed for MgCl2/ethanol mixture (Mix; 20’) and MgCl2. Exposure to MgCl2 dissolved in dw (1:1), to keep osmolarity at the same values of seawater, and Mix (45’) revealed the worst ability of octopus hearts to respond to preload increases, suggesting that these treatments may compromise the recovery from anaesthesia. Furthermore, heart perfusion with increasing concentrations of MgCl2 solutions revealed a dose-dependent decrease of heart rates (marked with MgCl2 1:1). Overall, these results give insights on cardiac action of MgCl2 formulations which may also contribute to the discussion of their implications as ‘anaesthetic’ agents in relation to the application of the new Directive 2010/63/EU to cephalopods