Impact of Lidocaine on Pain-Related Grooming in Cuttlefish

SIMPLE SUMMARY: Cuttlefish is an important species both in scientific and commercial use. To improve their welfare, assessments and reducing pain in animals are necessary. However, studies on nociception in cephalopods have so far focused on the octopus and squid, with no investigations with respect to our knowledge on cuttlefish. We used acetic acid to identify grooming, a key behaviour linked to pain in cuttlefish, as the assessment of pain and ascertained the efficacy of analgesics on pain perception in cuttlefish. We found that when more acetic acid is injected, increased grooming behaviour is induced in cuttlefish, and the injection of lidocaine reduced grooming behaviours in acetic-acid-injected cuttlefish; thus, we can recommend this drug for use as a local anesthetic. ABSTRACT: Nociception is the neural process of encoding noxious stimuli and is typically accompanied by a reflex withdrawal response away from the potentially injurious stimulus. Studies on nociception in cephalopods have so far focused on octopus and squid, with no investigations to our knowledge on cuttlefish. Yet, these are an important species both in scientific and commercial use. Therefore, the present study demonstrated that a standard pain stimulus, acetic acid, induced grooming behaviour directed towards the injection site in cuttlefish and that the injection of lidocaine reduces grooming behaviours in acetic-acid-injected cuttlefish. Wound-directed behaviour demonstrates that the animal is aware of the damage; thus, when subjecting these animals to any painful treatments in the laboratory, researchers should consider alleviating pain by the administration of pain-relieving drugs.