Three-dimensional molecular atlas highlights spatial and neurochemical complexity in the axial nerve cord of octopus arms.

Octopus arms, notable for their complex anatomy and remarkable flexibility, have sparked significant interest within the neuroscience community. However, there remains a dearth of knowledge about the neurochemical organization of various cell types in the arm's nervous system. To address this gap, we used hybridization chain reaction (HCR) to identify distinct neuronal types in the axial nerve cords of the pygmy octopus, Octopus bocki, including putative dopaminergic, octopaminergic, serotonergic, GABAergic, glutamatergic, cholinergic, and peptidergic cells.

Repeating ultrastructural motifs provide insight into the organization of the octopus arm nervous system.

The peripheral nervous system of the octopus is among the most complex of any animal. In each arm, hundreds of serial ganglia form a central core of nervous tissue processing sensory input, issuing motor commands, and exchanging information with the central brain. In addition to the central cord, there are two other types of neural elements: fine intramuscular nerve cords (INCs) and small sucker ganglia at the base of each sucker.

Perspective: Social License as a Lens for Improving Ethical and Welfare Standards in Cephalopod Research.

Interest in cephalopods as comparative models in neuroscience, cognition, behavior, and ecology is surging due to recent advances in culture and experimental techniques. Although cephalopods have a long history in research, their use had remained limited due to the challenges of funding work on comparative models, the lack of modern techniques applicable to them, and the small number of labs with the facilities to keep and house large numbers of healthy animals for long periods. Breakthroughs in each of these areas are now creating new interest in cephalopods from researchers who trained and worked in other models, as well as allowing established cephalopod labs to grow and collaborate more widely.

Post-injury pain and behaviour: a control theory perspective.

Injuries of various types occur commonly in the lives of humans and other animals and lead to a pattern of persistent pain and recuperative behaviour that allows safe and effective recovery. In this Perspective, we propose a control-theoretic framework to explain the adaptive processes in the brain that drive physiological post-injury behaviour. We set out an evolutionary and ethological view on how animals respond to injury, illustrating how the behavioural state associated with persistent pain and recuperation may be just as important as phasic pain in ensuring survival.

Evaluation of Candidates for Systemic Analgesia and General Anesthesia in the Emerging Model Cephalopod, .

Cephalopods' remarkable behavior and complex neurobiology make them valuable comparative model organisms, but studies aimed at enhancing welfare of captive cephalopods remain uncommon. Increasing regulation of cephalopods in research laboratories has resulted in growing interest in welfare-oriented refinements, including analgesia and anesthesia. Although general and local anesthesia in cephalopods have received limited prior study, there have been no studies of systemic analgesics in cephalopods to date.

Persistent nociceptor hyperactivity as a painful evolutionary adaptation.

Chronic pain caused by injury or disease of the nervous system (neuropathic pain) has been linked to persistent electrical hyperactivity of the sensory neurons (nociceptors) specialized to detect damaging stimuli and/or inflammation. This pain and hyperactivity are considered maladaptive because both can persist long after injured tissues have healed and inflammation has resolved. While the assumption of maladaptiveness is appropriate in many diseases, accumulating evidence from diverse species, including humans, challenges the assumption that neuropathic pain and persistent nociceptor hyperactivity are always maladaptive.

Behavioral changes in senescent giant Pacific octopus (Enteroctopus dofleini) are associated with peripheral neural degeneration and loss of epithelial tissue.

Most species of octopus experience extreme physical decline after a single reproductive bout which extends over a period of days, weeks, or months before eventual death. Although outward indicators of senescence are widely recognized, comparatively little is known about physiological and neural changes accompanying terminal decline in octopuses. Here, we measured changes in behavioral response to nociceptive stimuli across the lifespan in giant Pacific octopus (GPO), Enteroctopus dofleini, held in public aquariums in the USA.

Anesthetic Efficacy of Magnesium Chloride and Ethyl Alcohol in Temperate Octopus and Cuttlefish Species.

Cephalopods are important in biologic and biomedical research, yet relatively little objective information is available to guide researchers and veterinarians regarding the best methods for anesthetizing these animals for various experimental procedures. Recent studies demonstrate that ethyl alcohol and magnesium chloride are effective at depressing efferent and afferent neural signals in some tropical cephalopod species when measured via the pallial nerve. Here we used similar methods to test 2 temperate species ( and ) and demonstrate that (1) ethyl alcohol and magnesium chloride were effective at reversibly depressing evoked activity in the pallial nerve, (2) ethyl alcohol generally had shorter induction and recovery times compared with magnesium chloride, (3) both agents were associated with a latency between the behavioral and neural effects, and it was longer with magnesium chloride, and (4) senescent animals generally had longer induction or recovery times than young animals.

Behavioral and neurophysiological evidence suggests affective pain experience in octopus.

Pain is a negative affective state arising from tissue damage or inflammation. Because pain is aversive and its relief is innately rewarding, animals may learn to avoid a context in which pain is experienced and prefer one where pain relief occurs. It is generally accepted that vertebrate animals experience pain; however, there is currently inconclusive evidence that the affective component of pain occurs in any invertebrate.

Environmental estrogen exposure disrupts sensory processing and nociceptive plasticity in the cephalopod .

Endogenous estrogens affect multiple sensory systems, including those involved in processing noxious and painful stimuli. Extensive evidence demonstrates that estrogenic environmental pollutants have profound, negative effects on growth and reproductive physiology, but there is limited information about how estrogenic pollutants might affect sensory systems known to be modulated by endogenous estrogens. Here, we show that ethinyl estradiol, the most common artificial estrogen found in coastal marine environments, disrupts normal behavioral and neural responses to tissue injury in the sepiolid (Hawaiian bobtail squid), which inhabits shallow tropical waters close to dense human habitation.

Early-life injury produces lifelong neural hyperexcitability, cognitive deficit and altered defensive behaviour in the squid .

Injury occurring in the neonatal period in mammals is known to induce plasticity in pain pathways that may lead to pain dysfunction in later life. Whether these effects are unique to the mammalian nervous system is not well understood. Here, we investigate whether similar effects of early-life injury are found in a large-brained comparative model, the cephalopod .

Ontogenetic and Experience-Dependent Changes in Defensive Behavior in Captive-Bred Hawaiian Bobtail Squid, .

Cephalopod molluscs are known for their extensive behavioral repertoire and their impressive learning abilities. Their primary defensive behaviors, such as camouflage, have received detailed study, but knowledge is limited to intensive study of relatively few species. A considerable challenge facing cephalopod research is the need to establish new models that can be captive bred, are tractable for range of different experimental procedures, and that will address broad questions in biological research.

Recording of Neural and Behavioral Correlates of Anesthesia Induction, Reversal, and Euthanasia in Cephalopod Molluscs.

Cephalopod molluscs are among the most behaviorally and neurologically complex invertebrates. As they are now included in research animal welfare regulations in many countries, humane and effective anesthesia is required during invasive procedures. However, currently there is no evidence that agents believed to act as anesthetics produce effects beyond immobility.

Collectively Improving Our Teaching: Attempting Biology Department-wide Professional Development in Scientific Teaching.

Many efforts to improve science teaching in higher education focus on a few faculty members at an institution at a time, with limited published evidence on attempts to engage faculty across entire departments. We created a long-term, department-wide collaborative professional development program, Biology Faculty Explorations in Scientific Teaching (Biology FEST). Across 3 years of Biology FEST, 89% of the department's faculty completed a weeklong scientific teaching institute, and 83% of eligible instructors participated in additional semester-long follow-up programs.

The selective serotonin reuptake inhibitor fluoxetine increases spontaneous afferent firing, but not mechanonociceptive sensitization, in octopus.

Serotonin is a widely studied modulator of neural plasticity. Here we investigate the effect of fluoxetine, a selective serotonin reuptake inhibitor, on short-term, peripheral nociceptive plasticity in the neurologically complex invertebrate, octopus. After crush injury to isolated mantle (body wall) tissue, application of 10 nM fluoxetine increased spontaneous firing in crushed preparations, but had a minimal effect on mechanosensory sensitization.

Rapid Associative Learning and Stable Long-Term Memory in the Squid Euprymna scolopes.

Learning and memory in cephalopod molluscs have received intensive study because of cephalopods' complex behavioral repertoire and relatively accessible nervous systems. While most of this research has been conducted using octopus and cuttlefish species, there has been relatively little work on squid. Euprymna scolopes Berry, 1913, a sepiolid squid, is a promising model for further exploration of cephalopod cognition.

Peripheral injury alters schooling behavior in squid, Doryteuthis pealeii.

Animals with detectable injuries are at escalated threat of predation. The anti-predation tactic of schooling reduces individual predation risk overall, but it is not known how schooling behavior affects injured animals, or whether risks are reduced equally for injured animals versus other school members. In this laboratory study we examined the effects of minor fin injury on schooling decisions made by squid.

Persistent pain after spinal cord injury is maintained by primary afferent activity.

Chronic pain caused by insults to the CNS (central neuropathic pain) is widely assumed to be maintained exclusively by central mechanisms. However, chronic hyperexcitablility occurs in primary nociceptors after spinal cord injury (SCI), suggesting that SCI pain also depends upon continuing activity of peripheral sensory neurons. The present study in rats (Rattus norvegicus) found persistent upregulation after SCI of protein, but not mRNA, for a voltage-gated Na(+) channel, Nav1.

Neuroethology: self-recognition helps octopuses avoid entanglement.

How an octopus performs complex movements of its eight sucker-studded arms without entanglement has been a mystery. A new study has found that self-recognition of the octopus's skin by its suckers inhibits reflexive grasping of its own arms, simplifying the mechanisms needed to generate intricate arm behavior.

Nociceptive sensitization reduces predation risk.

Sublethal injury triggers long-lasting sensitization of defensive responses in most species examined, suggesting the involvement of powerful evolutionary selection pressures [1]. In humans, this persistent nociceptive sensitization is often accompanied by heightened sensations of pain and anxiety [2]. While experimental [3] and clinical [4] evidence support the adaptive value of immediate nociception during injury, no direct evidence exists for adaptive benefits of long-lasting sensitization after injury.

Arm injury produces long-term behavioral and neural hypersensitivity in octopus.

Cephalopod molluscs are the most neurally and behaviorally complex invertebrates, with brains rivaling those of some vertebrates in size and complexity. This has fostered the opinion that cephalopods, particularly octopuses, may experience vertebrate-like pain when injured. However, it is not known whether octopuses possess nociceptors or if their somatic sensory neurons exhibit sensitization after injury.

TRPV1 channels make major contributions to behavioral hypersensitivity and spontaneous activity in nociceptors after spinal cord injury.

Chronic neuropathic pain is often a severe and inadequately treated consequence of spinal cord injury (SCI). Recent findings suggest that SCI pain is promoted by spontaneous activity (SA) generated chronically in cell bodies of primary nociceptors in dorsal root ganglia (DRG). Many nociceptors express transient receptor potential V1 (TRPV1) channels, and in a preceding study most dissociated DRG neurons exhibiting SA were excited by the TRPV1 activator, capsaicin.

Squid have nociceptors that display widespread long-term sensitization and spontaneous activity after bodily injury.

Bodily injury in mammals often produces persistent pain that is driven at least in part by long-lasting sensitization and spontaneous activity (SA) in peripheral branches of primary nociceptors near sites of injury. While nociceptors have been described in lower vertebrates and invertebrates, outside of mammals there is limited evidence for peripheral sensitization of primary afferent neurons, and there are no reports of persistent SA being induced in primary afferents by noxious stimulation. Cephalopod molluscs are the most neurally and behaviorally complex invertebrates, with brains rivaling those of some vertebrates in size and complexity.

Spinal cord injury triggers an intrinsic growth-promoting state in nociceptors.

Although most investigations of the mechanisms underlying chronic pain after spinal cord injury (SCI) have examined the central nervous system (CNS), recent studies have shown that nociceptive primary afferent neurons display persistent hyperexcitability and spontaneous activity in their peripheral branches and somata in dorsal root ganglia (DRG) after SCI. This suggests that SCI-induced alterations of primary nociceptors contribute to central sensitization and chronic pain after SCI. Does SCI also promote growth of these neurons' fibers, as has been suggested in some reports? The present study tests the hypothesis that SCI induces an intrinsic growth-promoting state in DRG neurons.