Nociceptive Responses Research Articles

Optimizing anesthesia depth to enhance seizure quality during electroconvulsive therapy in major depressive disorder

This editorial evaluated the findings of a comprehensive study focused on the effects of anesthesia depth on seizure parameters during electroconvulsive therapy (ECT) in patients with major depressive disorder. The study utilized quantitative consciousness and quantitative nociceptive indices for monitoring sedation, hypnosis, and nociceptive responses. The analysis included 193 ECT sessions across 24 patients, revealing significant impacts of anesthesia depth on electroencephalography (EEG) seizure parameters. Key findings include that lighter anesthesia resulted in longer EEG seizure duration and higher post-ictal suppression index, without increasing complications. These insights emphasize the importance of optimal anesthesia management to improve therapeutic outcomes in ECT.

Effect of swearing on physical performance: a mini-review.

Swearing, or using taboo language with the potential to offend, has been shown to improve physical performance during short and intense tasks requiring strength and power development. While consistent ergogenic effects of swearing have been observed across studies, the mechanisms by which swearing impacts physical performance are not fully clear. Swearing has been shown to modulate physiological (i.e., heart rate, blood pressure, skin conductance), psychological (i.e., state disinhibition), and nociceptive (i.e., pain threshold, pain tolerance, pain perception) responses, thus making it plausible that these mechanisms allow swearing to positively impact physical performance. A variety of dosages of swearing (i.e., word used, intensity, frequency, quantity) have been reported to improve physical performance. Although habituation to the positive physical performance effects of swearing has not been explored formally through empirical research, habituation to swearing has been observed in other contexts. From a practical application standpoint, swearing represents a low-risk, effective, and inexpensive intervention that has the potential to acutely improve physical performance although the taboo nature of swearing may limit its utility in real-world situations. The purpose of the following review is to provide an overview of available evidence on swearing and physical performance and discuss likely underlying mechanisms. Exploration of different swearing approaches and habituation will also be highlighted and suggestions for future research will be discussed, to more comprehensively understand if swearing can be strategically used for performance enhancement.

Characterization of a rapid avoidance behavior in Manduca sexta larvae in response to noxious stimuli.

This study focuses on the nociceptive responses observed in the tobacco hornworm (Manduca sexta). While prior investigations have described the sensory neurons and muscle activation patterns associated with the 'strike' behavior, there remains a gap in our understanding of the alternative 'withdrawal' movement, wherein the animal bends its head and thorax away from the stimulus. Our results show that stimulus location determines which nocifensive behavior is elicited. Interestingly, stimulation of specific mid-body segments could result in either withdrawal or strike, indicating a decision process rather than a hard-wired circuit. The withdrawal behavior was characterized using high-speed videography and electromyography. The results show that withdrawal in Manduca is driven by contralateral ventral muscles, followed by an increase in ipsilateral muscle activation just before the bending stops. Dorsal muscles are co-activated throughout the movement. Although both withdrawal and strike behaviors involve sequential activation of lateral muscles, these behaviors involve different muscle groups. This discovery provides a novel model system to investigate the context-dependence and decision-making processes triggered by stressful or noxious stimuli.

Putative Nociceptive Responses in a Decapod Crustacean: The Shore Crab (Carcinus maenas).

Nociceptors are receptors that detect injurious stimuli and are necessary to convey such information from the periphery to the central nervous system. While nociception has been extensively studied in various taxa, there is relatively little electrophysiological evidence for the existence of nociceptors in decapod crustaceans. This study investigated putative nociceptive responses in the shore crabs, specifically their response to mechanical and noxious chemical stimuli. Extracellular multi-unit electrophysiological recordings were conducted from the anterior ganglion and the circumesophageal connective ganglia to assess nociceptive responses. Soft tissues at the joints of the chelae, antennae, and walking legs were stimulated using acetic acid (noxious stimulus) and von Frey hairs (mechanical stimulus), while nearby ganglion activity was recorded. The results indicate the existence of nociceptors in the tested areas, with mechanical stimuli eliciting shorter, more intense neural activity compared with acetic acid. Although acetic acid triggered responses in all areas, the antennae and antennules did not respond to mechanical stimuli. Though we acknowledge the challenges of conducting in vivo electrophysiological recordings, future research should focus on further characterizing nociceptor activity because the results suggest the presence of nociceptors.

High-Fat Diet-Induced Blood-Brain Barrier Dysfunction: Impact on Allodynia and Motor Coordination in Rats.

The associations among increased pain sensitivity, obesity, and systemic inflammation have not been described as related to BBB dysfunctions. To analyze the metabolic, behavioral, and inflammatory effects of a high-fat diet (HFD) and ultrastructural modifications in brain regions, we used an in vivo experimental model. Adult male Wistar rats were randomly assigned to one of two conditions, an ad libitum control group or an HFD (60%)-fed group, for eight weeks. At the end of the protocol, glucose and insulin tolerance tests were performed. Additionally, we analyzed the response to a normally innocuous mechanical stimulus and changes in motor coordination. At the end of the protocol, HFD-fed rats presented increased HOMA-IR and metabolic syndrome (MetS) prevalence. HFD-fed rats also developed an increased nociceptive response to mechanical stimuli and neurological injury, resulting in impaired motor function. Hypothalamus and cerebellum neurons from HFD-fed rats presented with nuclear swelling, an absence of nucleoli, and karyolysis. These results reveal that HFD consumption affects vital brain structures such as the cerebellum, hippocampus, and hypothalamus. This, in turn, could be producing neuronal damage, impairing cellular communication, and consequently altering motricity and pain sensitivity. Although direct evidence of a causal link between BBB dysfunction and sensory-motor changes was not observed, understanding the association uncovered in this study could lead to targeted therapeutic strategies.

Analgesic and Anti-Arthritic Potential of Methanolic Extract and Palmatine Obtained from Annona squamosa Leaves

Background/Objectives: Annona squamosa is used in folk medicine to treat pain and arthritis. Palmatine is an alkaloid isolated from several plants, including A. squamosa leaves. The aim of the present study was to investigate the analgesic, anti-arthritic, and anti-inflammatory potential of the methanolic extract of A. squamosa (EMAS) and palmatine. Methods: The chemical profile of EMAS was evaluated by ultra high-performance liquid chromatography with electrospray ionization coupled to mass spectrometry (UHPLC-ESI/MS). EMAS and palmatine were evaluated in carrageenan-induced pleurisy, zymosan-induced joint inflammation, formalin-induced nociception, and tumor necrosis factor (TNF)-induced mechanical hyperalgesia in experimental models in mice. A cytotoxicity test of EMAS and palmatine was performed using a methylthiazolidiphenyl-tetrazolium (MTT) bromide assay. Results: The analysis of the chemical profile of the extract showed the presence of palmatine, liriodenine, and anonaine. Oral administration of EMAS and palmatine significantly reduced leukocyte migration and oxide nitric production in the carrageenan-induced pleurisy model. EMAS and palmatine reduced mechanical hyperalgesia, leukocyte migration, and edema formation in the joint inflammation induced by zymosan. In the formalin test, palmatine was effective against the second-phase nociceptive response, mechanical hyperalgesia, and cold allodynia. In addition, palmatine reduced mechanical hyperalgesia induced by TNF. EMAS and palmatine did not demonstrate cytotoxicity. Conclusions: The present study showed that A. squamosa and palmatine are analgesic and anti-inflammatory agents, and that the anti-hyperalgesic properties of palmatine may involve the TNF pathway. Palmatine may be one of the compounds responsible for the anti-hyperalgesic and/or anti-arthritic properties of this medicinal plant.

High-frequency terahertz stimulation alleviates neuropathic pain by inhibiting the pyramidal neuron activity in the anterior cingulate cortex of mice.

Neuropathic pain (NP) is caused by a lesion or disease of the somatosensory system and is characterized by abnormal hypersensitivity to stimuli and nociceptive responses to non-noxious stimuli, affecting approximately 7-10% of the general population. However, current first-line drugs like non-steroidal anti-inflammatory agents and opioids have limitations, including dose-limiting side effects, dependence, and tolerability issues. Therefore, developing new interventions for the management of NP is urgent. In this study, we discovered that the high-frequency terahertz stimulation (HFTS) at approximately 36 THz effectively alleviates NP symptoms in mice with spared nerve injury. Computational simulation suggests that the frequency resonates with the carbonyl group in the filter region of Kv1.2 channels, facilitating the translocation of potassium ions. In vivo and in vitro results demonstrate that HFTS reduces the excitability of pyramidal neurons in the anterior cingulate cortex likely through enhancing the voltage-gated K+ and also the leak K+ conductance. This research presents a novel optical intervention strategy with terahertz waves for the treatment of NP and holds promising applications in other nervous system diseases.

Electroacupuncture Relieves Neuropathic Pain via Adenosine 3 Receptor Activation in the Spinal Cord Dorsal Horn of Mice.

Neuropathic pain (NPP) is a devastating and unbearable painful condition. As prevailing treatment strategies have failed to mitigate its complications, there remains a demand for effective therapies. Electroacupuncture (EA) has proved a potent remedial strategy in NPP management in humans and mammals. However, past studies have investigated the underlying mechanism of the analgesic effects of EA on NPP, focusing primarily on adenosine receptors in peripheral tissues. Herein, we elucidate the role of the adenosine (Adora-3) signaling pathway in mediating pain relief through EA in the central nervous system, which is obscure in the literature and needs exploration. Specific pathogen-free (SPF) male adult mice (C57BL/6 J) were utilized to investigate the effect of EA on adenosine metabolism (CD73, ADA) and its receptor activation (Adora-3), as potential mechanisms to mitigate NPP in the central nervous system. NPP was induced via spared nerve injury (SNI). EA treatment was administered seven times post-SNI surgery, and lumber (L4-L6) spinal cord was collected to determine the molecular expression of mRNA and protein levels. In the spinal cord of mice, following EA application, the expression results revealed that EA upregulated (p < 0.05) Adora-3 and CD73 by inhibiting ADA expression. In addition, EA triggered the release of adenosine (ADO), which modulated the nociceptive responses and enhanced neuronal activation. Meanwhile, the interplay between ADO levels and EA-induced antinociception, using an Adora-3 agonist and antagonist, showed that the Adora-3 agonist IB-MECA significantly increased (p < 0.05) nociceptive thresholds and expression levels. In contrast, the antagonist MRS1523 exacerbated neuropathic pain. Furthermore, an upregulated effect of EA on Adora-3 expression was inferred when the Adora-3 antagonist was administered, and the EA treatment increased the fluorescent intensity of Adora-3 in the spinal cord. Taken together, EA effectively modulates NPP by regulating the Adora-3 signaling pathway under induced pain conditions. These findings enhance our understanding of NPP management and offer potential avenues for innovative therapeutic interventions.

Statins ameliorate oxaliplatin- and paclitaxel-induced peripheral neuropathy via glutathione S-transferase

Some therapeutic agents have been found to have effects beyond their primary indications. Peripheral neuropathy, a common side effect of chemotherapy, remains inadequately treated. Identifying additional properties of existing medications could thus uncover novel therapeutic avenues. Previous studies have identified an additional effect of simvastatin in reducing neuropathy; however, the mechanism underlying this effect remains unclear. We investigated the novel effects of statins on chemotherapy-induced peripheral neuropathy in mice. Mice treated with oxaliplatin or paclitaxel did not show exacerbation or improvement in cold sensations upon acetone testing with statin administration. However, concurrent oral statin treatment mitigated the nociceptive response to mechanical stimuli induced by each anti-tumor agent. Co-administration of a glutathione S-transferase inhibitor, which modulates redox reactions, abolished the ameliorative effect of statins on mechanical nociceptive behavior. Additionally, the glutathione S-transferase inhibitor did not affect normal sensory perception or impair the anti-tumor effect of chemotherapy agents. A search for GST-associated molecules and pathways using artificial intelligence revealed that GST regulates inflammatory cytokines as a regulatory or causative gene. Our findings suggest that statins have class effects that ameliorate cytotoxic anti-cancer drug-induced mechanical allodynia via GST pathway activation.

A distinct neuronal ensemble of prelimbic cortex mediates spontaneous pain in rats with peripheral inflammation

The absence of a comprehensive understanding of the neural basis of spontaneous pain limits the development of therapeutic strategies targeting this primary complaint of patients with chronic pain. Here we report a distinct neuronal ensemble within the prelimbic cortex which processes signals related to spontaneous pain in rats with chronic inflammatory pain. This neuronal ensemble specifically encodes spontaneous pain-related behaviors, independently of other locomotive and evoked behaviors. Activation of this neuronal ensemble elicits marked spontaneous pain-like behaviors and enhances nociceptive responses, whereas prolonged silencing of its activities alleviates spontaneous pain and promotes overall recovery from inflammatory pain. Notably, afferents from the primary somatosensory cortex and infralimbic cortex bidirectionally modulate the activities of the spontaneous pain-responsive prelimbic cortex neuronal ensemble and pain behaviors. These findings reveal the cortical basis of spontaneous pain at the neuronal level, highlighting a distinct neuronal ensemble within the prelimbic cortex and its associated pain-regulatory brain networks.

Flexible Memristor Based on Lead‐Free Cs2AgBiBr6 Perovskite for Artificial Nociceptors and Information Security

AbstractThe emergence of the artificial intelligence urgently requires novel devices to handle massive data and bionic simulations. As one of new generation memory devices, memristor has great potential in information storage and brain‐like learning due to its merits, such as low energy consumption, high speed and etc. In addition, the randomness for the generation and breakage of the conducting filaments in the memristor can generate the true random numbers and realize the image encryption. In this work, the ITO/Cs2AgBiBr6/Al based devices exhibit prominent resistance variation characteristics and long‐term environmental stability (≥6 months). Additionally, the flexible PET/ITO/Cs2AgBiBr6/Al devices are assembled and measured resistance variation properties, which are adopt to realize the cryptographic processing of image information. The synaptic plasticity of the memristor is also verified, including paired pulse facilitation and spiking timing‐dependent plasticity. Finally, nociceptive responses are also simulated with the memristor via imposing different voltage. Nociceptive characteristics including “threshold,” “relaxation,” and “sensitization” have been successfully determined. The work provides possibility for lead‐free flexible perovskite memristors in information security and biomimicry.

Pregnancy ameliorates neuropathic pain through suppression of microglia and upregulation of the δ-opioid receptor in the anterior cingulate cortex in late-pregnant mice.

Pregnancy-induced analgesia develops in late pregnancy, but its mechanisms are unclear. The anterior cingulate cortex (ACC) plays a key role in the pathogenesis of neuropathic pain. The authors hypothesized that pregnancy-induced analgesia ameliorates neuropathic pain by suppressing activation of microglia and the expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, and by upregulating opioid receptors in the ACC in late-pregnant mice. Neuropathic pain was induced in non-pregnant (NP) or pregnant (P) C57BL/6JJmsSlc female mice by partial sciatic nerve ligation (PSNL). The nociceptive response was evaluated by mechanical allodynia and activation of microglia in the ACC was evaluated by immunohistochemistry. The expressions of phosphorylated AMPA receptors and opioid receptors in the ACC were evaluated by immunoblotting. In von Frey reflex tests, NP-PSNL-treated mice showed a lower 50% paw-withdrawal threshold than NP-Naïve mice on experimental day 9. No difference in 50% paw-withdrawal threshold was found among the NP-Naïve, NP-Sham, P-Sham, and P-PSNL-treated mice. The number of microglia in the ACC was significantly increased in NP-PSNL-treated mice compared to NP-Sham mice. Immunoblotting showed significantly increased expression of phosphorylated AMPA receptor subunit GluR1 at Ser831 in NP-PSNL-treated mice compared to NP-Sham mice. Immunoblotting also showed significantly increased δ-opioid receptor in the ACC in P-Sham and P-PSNL-treated mice compared to NP-Sham mice. Pregnancy-induced analgesia ameliorated neuropathic pain by suppressing activation of microglia and the expression of phosphorylated AMPA receptor subunit GluR1 at Ser831, and by upregulation of the δ-opioid receptor in the ACC in late-pregnant mice.

Pain anticipation is a new behavioural sign of minimally conscious state.

Probing cognition and consciousness in the absence of functional communication remains an extremely challenging task. In this perspective, we imagined a basic clinical procedure to explore pain anticipation at bedside. In a series of 61 patients with a disorder of consciousness, we tested the existence of a nociceptive anticipation response by pairing a somaesthetic stimulation with a noxious stimulation. We then explored how nociceptive anticipation response correlated with (i) clinical status inferred from Coma Recovery Scale-Revised scoring, (ii) with an EEG signature of stimulus anticipation-the contingent negative variation-and (iii) how nociceptive anticipation response could predict consciousness outcome at 6 months. Proportion of nociceptive anticipation response differed significantly according to the state of consciousness: nociceptive anticipation response was present in 5 of 5 emerging from minimally conscious state patients (100%), in 10 of 11 minimally conscious state plus patients (91%), but only in 8 of 17 minimally conscious state minus patients (47%), and only in 1 of 24 vegetative state/unresponsive wakefulness syndrome patients (4%) (χ 2 P < 0.0001). Nociceptive anticipation response correlated with the presence of a contingent negative variation, suggesting that patients with nociceptive anticipation response were more prone to actively expect and anticipate auditory stimuli (Fisher's exact test P = 0.05). However, nociceptive anticipation response presence did not predict consciousness recovery. Nociceptive anticipation response appears as a new additional behavioural sign that can be used to differentiate minimally conscious state from vegetative state/unresponsive wakefulness syndrome patients. As most behavioural signs of minimally conscious state, the nociceptive anticipation response seems to reveal the existence of a cortically mediated state that does not necessarily reflect residual conscious processing.

Insights into Vincristine-Induced Peripheral Neuropathy in Aged Rats: Wallerian Degeneration, Oxidative Damage, and Alterations in ATPase Enzymes.

This study aimed to elucidate vincristine (VCR)-induced peripheral neuropathy in aged rats, a poorly understood neurotoxicity. Both young and old Wistar rats were administered VCR (0.1 mg/kg, intraperitoneally (i.p.)) and compared to age-matched controls (0.9% saline; 10 mg/mL, i.p.). Mechanical (MN) and thermal nociceptive (TN) responses were assessed on days 0, 6, 11, and 17. Locomotor response, cognitive ability, and anxious-like behavior were evaluated on days 14, 15, and 16. Results showed MN and TN responses in both young and old VCR-exposed rats. In old rats, VCR exacerbated MN (on days 6, 11, and 17) and TN (on days 6 and 17) responses. VCR also induced cognitive impairments and anxiety-like behavior. Histological analysis revealed Wallerian degeneration in the spinal cords of VCR-exposed rats accompanied by macrophage migration. Furthermore, VCR increased Ca2+-ATPase activity while inhibiting Na+, K+-ATPase activity in young and old rats. VCR altered the homeostasis of Mg2+-ATPase activity. Lipid peroxidation and nitrite and nitrate levels increased in young and old rats exposed to VCR. This study provides valuable insights into VCR's mechanistic pathways in aged rats, emphasizing the need for further research in this area.

Antiarthritic and Antinociceptive Properties of Ylang-Ylang (Cananga odorata) Essential Oil in Experimental Models.

The aim of this study was to evaluate the effect of ylang-ylang (Cananga odorata) essential oil (YEO) on models of experimental arthritis, persistent inflammation, and nociception in mice. YEO treatment at doses of 100 and 200 mg/kg reduced the infiltration of leukocytes into the joint cavities of mice submitted to zymosan-induced arthritis 6 h and 7 days after arthritis induction. At these doses, YEO treatment reduced the formation of joint edema 4 and 6 h after arthritis induction, and at a dose of 200 mg/kg, YEO treatment reduced mechanical hyperalgesia 3 and 4 h after arthritis induction. At the dose of 200 mg/kg, YEO treatment reduced interleukin-6 (IL-6) levels and cartilage destruction in the zymosan-induced arthritis model, and reduced edema formation and mechanical hyperalgesia in the model of persistent inflammation (21 days) induced by complete Freund's adjuvant (CFA) in mice. YEO treatment at a dose of 200 mg/kg reduced the nociceptive response in experimental models of nociception induced by acetic acid and formalin. The YEO treatment reduced inflammatory parameters in the experimental arthritis model, and presented antiarthritic, anti-hyperalgesic, antinociceptive, and anti-inflammatory properties.

Endocannabinoids regulate enteric neuron-glia networks and visceral hypersensitivity following inflammation through a glial-dependent mechanism.

Acute gastrointestinal (GI) inflammation induces neuroplasticity that produces long-lasting changes in gut motor function and pain. The endocannabinoid system is an attractive target to correct pain and dysmotility, but how inflammation changes endocannabinoid control over cellular communication in enteric neurocircuits is not understood. Enteric glia modulate gut neurons that control motility and pain and express monoacylglycerol lipase (MAGL) which controls endocannabinoid availability. We used a combination of in situ calcium imaging, chemogenetics, and selective drugs to study how endocannabinoid mechanisms affect glial responses and subsequent enteric neuron activity in health and following colitis in Wnt1Cre;GCaMP5g-tdT;GFAP::hM3Dq mice. Trpv1Cre;GCaMP5gtdT mice were used to study nociceptor sensitivity and Sox10CreERT2;Mgllf/f mice were used to test the role of glial MAGL in visceral pain. The data show that endocannabinoid signaling regulates neuro-glial signaling in gut neurocircuits in a sexually dimorphic manner. Inhibiting MAGL in healthy samples decreased glial responsiveness but this effect was lost in females following colitis and converted to an excitatory effect in males. Manipulating CB1 and CB2 receptors revealed further sex differences amongst neuro-glia signaling that were impacted following inflammation. Inflammation increased gut nociceptor sensitivity in both sexes but only females exhibited visceral hypersensitivity in vivo. Blocking MAGL normalized nociceptor responses in vitro and deleting glial Mgll in vivo rescued visceral hypersensitivity in females. These results show that sex and inflammation impact endocannabinoid mechanisms that regulate intercellular enteric glia-neuron communication. Further, targeting glial MAGL could provide therapeutic benefits for visceral nociception in a sex-dependent manner.

Rosacea in East Asian populations: Clinical manifestations and pathophysiological perspectives for accurate diagnosis.

Rosacea is a chronic inflammatory disorder primarily affecting the facial skin, prominently involving the cheeks, nose, chin, forehead, and periorbital area. Cutaneous manifestations encompass persistent facial erythema, phymas, papules, pustules, telangiectasia, and flushing. The pathogenesis of rosacea is associated with various exacerbating or triggering factors, including microbial infestation, temperature fluctuations, sunlight exposure, physical exertion, emotional stress, consumption of hot beverages and spicy foods, and exposure to airborne pollen. These environmental factors interact with genetic predispositions in the development of rosacea. The roles of the lipophilic microbiome, ultraviolet radiation, nociceptive responses, and vascular alterations have been proposed as significant factors in the pathogenesis. These insights contribute to understanding the anatomical specificity of facial involvement and the progressive nature of rosacea. East Asian skin, predominantly classified as Fitzpatrick skin phototypes III to IV, is characterized by relatively diminished skin barrier function and increased sensitivity to irritants. Airborne pollen exposure may particularly act as a trigger in East Asian individuals, possibly mediated through toll-like receptors. The lack of specificity in objective clinical and histopathological findings leads to diagnostic challenges for individuals with colored skin, including East Asians, particularly when erythema is the sole objective manifestation. An alternative diagnostic scheme may thus be necessary. A diagnostic approach emphasizing vascular manifestations and nociceptive symptoms potentially holds promise for individuals with darker skin tones. More research focusing on potential variations in skin physiology across different racial groups is essential to establish more effective diagnostic schemes applicable to both dark and light skin colors.

Mechanical Nociception Assay in Drosophila Larvae.

The nervous system of animals can sense and respond to noxious stimuli, which include noxious thermal, chemical, or mechanical stimuli, through a process called nociception. Here, we describe a simple behavioral assay to measure mechanically induced nociceptive responses in Drosophila larvae. This assay tests larval mechanosensitivity to noxious force with calibrated von Frey filaments. First, we explain how to construct and calibrate the customizable von Frey filaments that can be used to deliver reproducible stimuli of a defined force or pressure. Next, we describe how to perform the mechanical nociception assay on third-instar larvae. Through comparison of the responses of genotypes of interest, this assay can be useful for investigation of molecular, cellular, and circuit mechanisms of mechanical nociception. At the molecular level, prior studies have identified the importance of sensory ion channels such as Pickpocket/Balboa, Piezo, dTRPA1, and Painless. At the cellular level, the class IV multidendritic arborizing (md-da) neurons are the main mechanical nociceptor neurons of the peripheral system, but class III and class II md-da have been found to also play a role. At the circuit level, studies have shown that mechanical nociception relies on interneurons of the abdominal ganglia that integrate inputs from these various md-da neuron classes.

Optogenetic Stimulation of Nociceptive Escape Behaviors in Drosophila Larvae.

In animals, noxious stimuli activate a neural process called nociception. Drosophila larvae perform a rolling escape locomotion behavior in response to nociceptive sensory stimuli. Noxious mechanical, thermal, and chemical stimuli each trigger this same escape response in larvae. The polymodal sensory neurons that initiate the rolling response have been identified based on the expression patterns of genes that are known to be required for nociception responses. The synaptic output of these neurons, known as class IV multidendritic sensory neurons, is required for behavioral responses to thermal, mechanical, and chemical triggers of the rolling escape locomotion. Importantly, optogenetic stimulation of the class IV multidendritic neurons has also shown that the activation of those cells is sufficient to trigger nociceptive rolling. Optogenetics uses light-activated ion channels expressed in neurons of interest to bypass the normal physiological transduction machinery so that the cell may be activated in response to light that is applied by the investigator. This protocol describes an optogenetic technique that uses channelrhodopsin-2 (ChR2) to activate larval nociceptors and trigger nociceptive rolling. First, we explain how to set up the necessary genetic crosses and culture the larval progeny. Next, we describe how to perform the optogenetic nociception assay on third-instar larvae.

Assaying Nociception Behaviors in Drosophila Larvae During Parasitoid Wasp Attacks.

Nociception in fruit fly (Drosophila melanogaster) larvae is characterized by a stereotyped escape behavior. When a larva encounters a noxious (potentially harmful) stimulus, it responds by curving its body into a c-shape and rolling in a corkscrew-like manner around its long-body axis. This rolling behavior may serve to quickly remove the larva from the source of the noxious stimulus, and is particularly adaptive to escape from a common natural predator of fruit fly larvae: parasitoid wasps (Leptopilina boulardi). L. boulardi completes its life cycle by using fruit fly larvae as hosts for its offspring. Female wasps sting fly larvae with an ovipositor and lay an egg within the larva. The wasp offspring hatches inside the fly larva, consumes the fly tissues during pupation, and eventually emerges from the pupal case as an adult wasp. Fruit fly larvae respond to oviposition attacks by rolling, which causes the long flexible ovipositor to be wound around the larval body like a spool. This dislodges the wasp and allows the larva to attempt to escape by crawling. Rolling behavior is triggered by the activation of sensory neurons (nociceptors) whose function can inform our understanding of the mechanisms of nociception. In this protocol, we describe a simple behavioral assay to test and measure nociceptive responses in Drosophila larvae during oviposition attacks by female parasitoid wasps. First, we discuss parasitoid wasp husbandry and culturing methods in the laboratory. We then describe how to perform the wasp nociception assay on third-instar fruit fly larvae.