Cephalopods in neuroscience: regulations, research and the 3Rs

Cephalopods have been utilised in neuroscience research for more than 100 years particularly because of their phenotypic plasticity, complex and centralised nervous system, tractability for studies of learning and cellular mechanisms of memory (e.g. long-term potentiation) and anatomical features facilitating physiological studies (e.g. squid giant axon and synapse). On 1 January 2013, research using any of the about 700 extant species of "live cephalopods" became regulated within the European Union by Directive 2010/63/EU on the "Protection of Animals used for Scientific Purposes", giving cephalopods the same EU legal protection as previously afforded only to vertebrates. The Directive has a number of implications, particularly for neuroscience research. These include: (1) projects will need justification, authorisation from local competent authorities, and be subject to review including a harm-benefit assessment and adherence to the 3Rs principles (Replacement, Refinement and Reduction). (2) To support project evaluation and compliance with the new EU law, guidelines specific to cephalopods will need to be developed, covering capture, transport, handling, housing, care, maintenance, health monitoring, humane anaesthesia, analgesia and euthanasia. (3) Objective criteria need to be developed to identify signs of pain, suffering, distress and lasting harm particularly in the context of their induction by an experimental procedure. Despite diversity of views existing on some of these topics, this paper reviews the above topics and describes the approaches being taken by the cephalopod research community (represented by the authorship) to produce "guidelines" and the potential contribution of neuroscience research to cephalopod welfare.

Molecular analysis of FMRFamide- and FMRFamide-related peptides (FaRPS) in the cuttlefish Sepia officinalis

The display of complex color patterns of the cuttlefish Sepia officinalis is under the regulation of the FMRFamide-related peptide (FaRP) family, but their exact identities are unknown. We report the isolation and characterization of a full-length FaRP cDNA from the brain of S. officinalis. This cDNA is 1850 base pairs long, including an open reading frame of 996 base pairs. The cDNA encodes a precursor protein containing four FaRPs: ALSGDAFLRF, FIRF, FLRF and FMRF. Each propeptide has a C-terminal glycine residue that is presumably converted post-translationally to an amide. Every FaRP propeptide is also flanked by basic amino acid residues at the amino and carboxy termini, indicative of putative cleavage sites during post-translational processing. Each of the four FaRPs encoded by this cDNA causes chromatophore expansion when assayed in an in vitro chromatophore bioassay. Thus, it is likely that one or more of the FaRPs identified in this study are involved in controlling chromatophore activity in cuttlefish.

Peptidergic regulation of chromatophore function in the European cuttlefish Sepia officinalis

Color patterning in cephalopod molluscs involves activation of a peripheral chromatophore system that is under neuromuscular control. The complex behavior of individual chromatophores is mediated by a specific set of muscles, the chromatophore muscles, that receive direct innervation from the central nervous system. To date, glutamate is the only excitatory transmitter that has been proposed to act at the chromatophore neuromuscular junction of cephalopods. We present data demonstrating that the chromatophore muscles in the European cuttlefish Sepia officinalis are also regulated by the FMRFamide family of neuropeptides. Using an in vitro chromatophore bioassay, it has been determined that several FMRFamide-related peptides (FaRPs) are potent excitors of the chromatophore muscles, causing chromatophore expansion. Immunocytochemical analyses of the central nervous system using an FMRFamide antibody revealed the presence of FMRFamide-like immunoreactive cell bodies in the posterior chromatophore lobes, the region of the brain containing the chromatophore motoneurons of the fin and mantle. FMRFamide-like immunoreactivity was also seen in the periphery, in the nerves around the chromatophores and in close apposition to the muscles in the chromatophore layer of the fin. HPLC analysis of the fin dermis isolated four bioactive peaks that were FMRFamide-immunoreactive when tested on an immunoblot assay. Two of these peaks co-eluted with known FaRPs, FMRFamide and ALSGDAFLRFamide, a decapeptide isolated from squid. Taken together, these data suggest that the FaRPs are likely to be endogenous excitors of the chromatophore muscles in cephalopods.

From behavior to molecules: an integrated approach to the study of neuropeptides

Despite extensive information on many aspects of peptide neurobiology, the links between the behavioral effects of neuropeptides and their actions at the cellular and molecular levels are not fully understood. A pair of insect neuropeptides, the cardioacceleratory peptides (CAPs) of the tobacco hawkmoth Manduca sexta, provide an opportunity to elucidate these links. The CAPs are involved in the modulation of four distinct types of behavior during the life cycle of this moth. Functional differences at these four developmental periods can be explained by stage-specific changes in target sensitivity and the distribution of the CAP-containing neurons, including a set of peptidergic neurons that alter their transmitter phenotype postembryonically. Studies show that inositol 1, 4, 5-trisphosphate (IP3), linked to intracellular Ca2+, mediates the response of the cells to the CAPs. This preparation thus provides additional insights into the mechanisms underlying the action of multifunctional neuropeptides.

Insect cardioactive peptides: neurohormonal regulation of cardiac activity by two cardioacceleratory peptides during flight in the tobacco hawkmoth, Manduca sexta

The relationship between two cardioactive neuropeptides, the cardioacceleratory peptides (CAPs), and changes in heart rate during flight was investigated in the tobacco hawkmoth, Manduca sexta. In vivo heart recordings from intact, tethered adults revealed a marked increase in heart rate associated with flying. Both anterior-to-posterior and posterior-to-anterior contraction waves showed a measurable elevation in contraction frequency. These changes in heart activity were noted in animals engaged in short (20 min) or long (60 min) bouts of continuous flight. Bioassay of blood taken from flying animals revealed the presence of an activity-dependent, blood-borne cardioacceleratory factor(s). Biochemical analyses of the blood of flying insects on HPLC identified two cardioacceleratory factors which co-eluted with the two CAPs. A depletion in the ventral nerve cord levels of both CAPs was observed during flight. In vivo injections of an anti-CAP monoclonal antibody blocked the increase in cardiac activity associated with flight. These results confirm the hypothesis that both CAPs act as cardioregulatory neurohormones during flight in Manduca sexta.