RESUMO
Carnosine is a naturally occurring endogenous dipeptide with well-recognized anti-inflammatory, antioxidant, and neuroprotective effects at the central nervous system level. To date, very few studies have been focused on the ability of carnosine to rescue and/or enhance memory. Here, we used a well-known invertebrate model system, the pond snail Lymnaea stagnalis, and a well-studied associative learning procedure, operant conditioning of aerial respiration, to investigate the ability of carnosine to enhance long-term memory (LTM) formation and reverse memory obstruction caused by an immune challenge (i.e., lipopolysaccharide [LPS] injection). Exposing snails to 1 mM carnosine for 1 h before training in addition to enhancing memory formation resulted in a significant upregulation of the expression levels of key neuroplasticity genes (i.e., glutamate ionotropic receptor N-methyl-d-aspartate [NMDA]-type subunit 1-LymGRIN1, and the transcription factor cAMP-response element-binding protein 1-LymCREB1) in snails' central ring ganglia. Moreover, pre-exposure to 1 mM carnosine before an LPS injection reversed the memory deficit brought about by inflammation, by preventing the upregulation of key targets for immune and stress response (i.e., Toll-like receptor 4-LymTLR4, molluscan defense molecule-LymMDM, heat shock protein 70-LymHSP70). Our data are thus consistent with the hypothesis that carnosine can have positive benefits on cognitive ability and be able to reverse memory aversive states induced by neuroinflammation.
Assuntos
Carnosina , Lipopolissacarídeos , Lymnaea , Memória de Longo Prazo , Animais , Lymnaea/efeitos dos fármacos , Carnosina/farmacologia , Memória de Longo Prazo/efeitos dos fármacos , Memória de Longo Prazo/fisiologia , Lipopolissacarídeos/farmacologia , Gânglios dos Invertebrados/efeitos dos fármacos , Gânglios dos Invertebrados/metabolismo , Plasticidade Neuronal/efeitos dos fármacos , Plasticidade Neuronal/fisiologia , Condicionamento Operante/efeitos dos fármacos , Comportamento Animal/efeitos dos fármacosRESUMO
Linked rhythmic behaviors, such as respiration/locomotion or swallowing/chewing, often require coordination for proper function. Despite its prevalence, the cellular mechanisms controlling coordination of the underlying neural networks remain undetermined in most systems. We use the stomatogastric nervous system of the crab Cancer borealis to investigate mechanisms of internetwork coordination, due to its small, well-characterized feeding-related networks (gastric mill [chewing, â¼0.1â Hz]; pyloric [filtering food, â¼1â Hz]). Here, we investigate coordination between these networks during the Gly1-SIFamide neuropeptide modulatory state. Gly1-SIFamide activates a unique triphasic gastric mill rhythm in which the typically pyloric-only LPG neuron generates dual pyloric-plus gastric mill-timed oscillations. Additionally, the pyloric rhythm exhibits shorter cycles during gastric mill rhythm-timed LPG bursts, and longer cycles during IC, or IC plus LG gastric mill neuron bursts. Photoinactivation revealed that LPG is necessary to shorten pyloric cycle period, likely through its rectified electrical coupling to pyloric pacemaker neurons. Hyperpolarizing current injections demonstrated that although LG bursting enables IC bursts, only gastric mill rhythm bursts in IC are necessary to prolong the pyloric cycle period. Surprisingly, LPG photoinactivation also eliminated prolonged pyloric cycles, without changing IC firing frequency or gastric mill burst duration, suggesting that pyloric cycles are prolonged via IC synaptic inhibition of LPG, which indirectly slows the pyloric pacemakers via electrical coupling. Thus, the same dual-network neuron directly conveys excitation from its endogenous bursting and indirectly funnels synaptic inhibition to enable one network to alternately decrease and increase the cycle period of a related network.
Assuntos
Braquiúros , Gânglios dos Invertebrados , Neurônios , Neuropeptídeos , Animais , Braquiúros/fisiologia , Neuropeptídeos/farmacologia , Neuropeptídeos/metabolismo , Neurônios/fisiologia , Neurônios/efeitos dos fármacos , Gânglios dos Invertebrados/fisiologia , Gânglios dos Invertebrados/efeitos dos fármacos , Potenciais de Ação/fisiologia , Potenciais de Ação/efeitos dos fármacos , Rede Nervosa/fisiologia , Rede Nervosa/efeitos dos fármacos , Masculino , Comportamento Alimentar/fisiologia , Comportamento Alimentar/efeitos dos fármacos , Piloro/fisiologia , Piloro/efeitos dos fármacos , PeriodicidadeRESUMO
When crayfish have attained dominant status after agonistic bouts, their avoidance reaction to mechanical stimulation of the tailfan changes from a dart to a turn response. Ascending interneurones originating in the terminal ganglion receive sensory inputs from the tailfan and they affect spike activity of both uropod and abdominal postural motor neurones, which coordinates the uropod and abdominal postural movements. Despite the varying output effects of ascending interneurones, the synaptic responses of all interneurones to sensory stimulation were enhanced when they acquired a dominant state. The number of spikes increased as did a sustained membrane depolarizations. Regardless of social status, the output effects on the uropod motor neurones of all interneurones except VE-1 remained unchanged. VE-1 mainly inhibited the uropod opener motor neurones in naive animals, but tended to excite them in dominant animals. Synaptic enhancement of the sensory response of ascending interneurones was also observed in naive animals treated with bath-applied serotonin. However, subordinate animals or naive animals treated with octopamine had no noticeable effect on the synaptic response of their ascending interneurones to sensory stimulation. Thus, enhancement of the synaptic response is a specific neural event that occurs when crayfish attain social dominance and it is mediated by serotonin.
Assuntos
Astacoidea/fisiologia , Comportamento Animal , Gânglios dos Invertebrados/fisiologia , Plasticidade Neuronal , Predomínio Social , Transmissão Sináptica , Comportamento Agonístico , Animais , Astacoidea/efeitos dos fármacos , Aprendizagem da Esquiva , Gânglios dos Invertebrados/efeitos dos fármacos , Interneurônios/efeitos dos fármacos , Interneurônios/fisiologia , Masculino , Neurônios Motores/efeitos dos fármacos , Neurônios Motores/fisiologia , Plasticidade Neuronal/efeitos dos fármacos , Octopamina/farmacologia , Serotonina/farmacologia , Potenciais Sinápticos , Transmissão Sináptica/efeitos dos fármacosRESUMO
Under extreme environmental conditions, many insects enter a protective coma associated with a spreading depolarization (SD) of neurons and glia in the central nervous system (CNS). Recovery depends on the restoration of ion gradients by mechanisms that are not well understood. We investigated the effects of glybenclamide, an ATP-sensitive K+ (KATP) channel inhibitor, and pinacidil, a KATP activator, on the mechanisms involved in anoxic coma induction and recovery in Locusta migratoria. KATP channels allow for the efflux of K+ when activated, thereby linking cellular metabolic state to membrane potential. In intact locusts, we measured the time to enter a coma after water immersion and the time to recover the righting reflex after returning to normoxia. In semi-intact preparations, we measured the time to SD in the metathoracic ganglion after flooding the preparation with saline or exposing it to 100% N2 gas, and the time for the transperineurial potential to recover after removal of the saline or return to air. Glybenclamide decreased the time to coma induction, whereas pinacidil increased induction times. Glybenclamide also lengthened the time to recovery and decreased the rate of recovery of transperineurial potential after SD. These results were not the same as the effects of 10-2 M ouabain on N2-induced SD. We conclude that glybenclamide affects the CNS response to anoxia via inhibition of KATP channels and not an effect on the Na+/K+-ATPase.NEW & NOTEWORTHY We demonstrate the involvement of ATP-sensitive K+ (KATP) channels during recovery from spreading depolarization (SD) induced via anoxic coma in locusts. KATP inhibition using glybenclamide impaired ion homeostasis across the blood-brain barrier resulting in a longer time to recovery of transperineurial potential following SD. Comparison with ouabain indicates that the effects of glybenclamide are not mediated by the Na+/K+-ATPase but are a result of KATP channel inhibition.
Assuntos
Coma , Excitabilidade Cortical/fisiologia , Gânglios dos Invertebrados/fisiologia , Hipóxia , Canais KATP/metabolismo , Potenciais da Membrana/fisiologia , Bloqueadores dos Canais de Potássio/farmacologia , Animais , Coma/metabolismo , Coma/fisiopatologia , Excitabilidade Cortical/efeitos dos fármacos , Feminino , Gânglios dos Invertebrados/efeitos dos fármacos , Glibureto/farmacologia , Hipóxia/metabolismo , Hipóxia/fisiopatologia , Canais KATP/antagonistas & inibidores , Locusta migratoria , Masculino , Potenciais da Membrana/efeitos dos fármacosRESUMO
Thoracic ganglia of many hearing insects house the first level of auditory processing. In bush-crickets, the largest population of local auditory neurons in the prothoracic processing centre are dorsal unpaired median (DUM) neurons. It has been suggested that DUM neurons are inhibitory using γ-aminobutyric acid (GABA) as transmitter. Immunohistochemistry reveals a population of about 35-50 GABA-positive somata in the posterior medial cluster of the prothoracic ganglion. Only very few small somata in this cluster remain unstained. At least 10 neurites from 10 neurons can be identified. Intracellularly stained auditory DUM neurons have their soma in the cluster of median GABA positive cells and most of them exhibit GABA-immunoreactivity. Responses of certain DUM neurons show obvious signs of inhibition. Application of picrotoxin (PTX), a chloride-channel blocker in insects, changes the responses of many DUM neurons. They become broader in frequency tuning and broader or narrower in temporal pattern tuning. Furthermore, inhibitory postsynaptic potentials (IPSPs) may be replaced by excitatory postsynaptic potentials. Loss of an IPSP in the rising graded potential after PTX-application leads to a significant reduction of first-spike latency. Therefore, auditory DUM neurons receive effective inhibition and are the best candidates for inhibition in DUM neurons and other auditory interneurons.
Assuntos
Gryllidae/fisiologia , Picrotoxina/farmacologia , Estimulação Acústica , Animais , Vias Auditivas/efeitos dos fármacos , Vias Auditivas/fisiologia , Percepção Auditiva/efeitos dos fármacos , Percepção Auditiva/fisiologia , Potenciais Pós-Sinápticos Excitadores , Feminino , Antagonistas GABAérgicos/farmacologia , Gânglios dos Invertebrados/efeitos dos fármacos , Gânglios dos Invertebrados/fisiologia , Gryllidae/efeitos dos fármacos , Potenciais Pós-Sinápticos Inibidores , Masculino , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Ácido gama-Aminobutírico/química , Ácido gama-Aminobutírico/metabolismoRESUMO
(1) The effect of tannic acid (TA), a dominant component of plant allelochemicals, was investigated on the locomotion and feeding of the pond snail, Lymnaea stagnalis. The effect of TA on the neuronal background underlying feeding activity was also analysed. (2) TA affected the spontaneous locomotion and of juvenile snails in a concentration-dependent way. Low (10 µM) TA concentration resulted in an increased (sliding or swimming) activity compared to the control; meanwhile, high (100 µM) TA concentration inhibited the locomotion of the animals. (3) Low (10 µM) TA concentration increased the frequency of sucrose-evoked feeding of intact animals, whereas high (100 µM) TA concentration resulted in significantly longer feeding latency and decreased feeding rate. The feeding changes proved to be partially irreversible, since after 48 h maintained in clear water, the animals tested in 100 µM TA previously still showed lower feeding rate in sucrose. (4) Electrophysiological experiments on semi-intact preparations showed that application of 100 µM TA to the lip area inhibited the fictive feeding pattern of central neurons, the cellular response to sucrose. (5) On isolated CNS preparation, 100 µM TA applied in the bathing solution, however, failed to inhibit the activation of the central feeding (CPG) interneurons following application of extracellular dopamine. Our results suggest that TA affects both afferent and efferent peripheral functions in Lymnaea. TA reduces feeding activity by primarily blocking feeding sensory pathways, and its negative effect on locomotion may imply sensory pathways and/or ciliary activity.
Assuntos
Comportamento Alimentar/efeitos dos fármacos , Locomoção/efeitos dos fármacos , Lymnaea/efeitos dos fármacos , Taninos/toxicidade , Animais , Gânglios dos Invertebrados/efeitos dos fármacos , Lymnaea/fisiologiaRESUMO
Cannabis sativa, also known as marijuana or hemp, produces a non-psychoactive compound cannabidiol (CBD). To investigate the defensive role of CBD, a feeding preference assay was performed with tobacco hornworm Manduca sexta. The larvae clearly show feeding preference towards the Cannabis tissue containing low CBD over high CBD. While the larva avoided the high CBD diet, we investigated detrimental effects of CBD in the insects' diet. Contrasted to the performance on low CBD-infused artificial diet (AD), larvae reared on the high CBD diet suffer significantly reduced growth and increased mortality. Through testing different carriers, we found that the increase of EtOH in the diet is negatively correlated with insect development and behaviors. Notably, CBD treatment significantly improved ethanol-intoxicated larval survival rate by 40% and also improved diet searching activity, resulting in increased diet consumption. Electrophysiology results revealed that the CBD-treated ganglia had delayed but much larger response with electric stimuli in comparison to the larvae reared on AD only and EtOH-added diet. Our results show CBDs' defensive role against pest insects, which suggests its possible use as an insecticide. We also provide evidence that CBD alleviates alcohol-induced stress; consequently, improving the performance and viability of M. sexta larvae.
Assuntos
Canabidiol/farmacologia , Etanol/farmacologia , Inseticidas/farmacologia , Manduca/efeitos dos fármacos , Animais , Fenômenos Eletrofisiológicos/efeitos dos fármacos , Etanol/antagonistas & inibidores , Gânglios dos Invertebrados/efeitos dos fármacos , Larva/efeitos dos fármacos , MasculinoRESUMO
Sensory feedback shapes ongoing behavior and may produce learning and memory. Motor responses to edible or inedible food in a reduced Aplysia preparation were examined to test how sensory feedback affects behavior and memory. Feeding patterns were initiated by applying a cholinomimetic onto the cerebral ganglion. Feedback from buccal muscles increased the response variability and response rate. Repeated application of the cholinomimetic caused decreased responses, expressed in part by lengthening protractions. Swallowing strips of "edible" food, which in intact animals induces learning that enhances ingestion, increased the response rate, and shortened the protraction length, reflecting more swallowing. Testing memory by repeating the procedure prevented the decrease in response rate observed with the cholinomimetic alone, and shortened protractions. Training with "inedible" food that in intact animals produces learning expressed by decreased responses caused lengthened protractions. Testing memory by repeating the procedure did not cause decreased responses or lengthened protractions. After training and testing with edible or inedible food, all preparations were exposed to the cholinomimetic alone. Preparations previously trained with edible food displayed memory expressed as decreased protraction length. Preparations previously trained with inedible food showed decreases in many response parameters. Memory for inedible food may arise in part via a postsynaptic decrease in response to acetylcholine released by afferents sensing food. The lack of change in response number, and in the time that responses are maintained during the two training sessions preceding application of the cholinomimetic alone suggests that memory expression may differ from behavioral changes during training.
Assuntos
Deglutição/fisiologia , Retroalimentação Sensorial/fisiologia , Comportamento Alimentar/fisiologia , Gânglios dos Invertebrados/fisiologia , Memória/fisiologia , Neurônios/fisiologia , Animais , Aplysia , Carbacol/administração & dosagem , Agonistas Colinérgicos/administração & dosagem , Deglutição/efeitos dos fármacos , Retroalimentação Sensorial/efeitos dos fármacos , Comportamento Alimentar/efeitos dos fármacos , Gânglios dos Invertebrados/efeitos dos fármacos , Memória/efeitos dos fármacos , Propriocepção/efeitos dos fármacos , Propriocepção/fisiologiaRESUMO
CONTEXT: Homology modeling plays role in determining the therapeutic targets dreadful for condition such as neurodegenerative diseases (NDD), which pose challenge in achieving the effective managements. The structures of the serotonin transporter (SERT), aquaporin (AQP), and tropomyosin receptor kinase (TrkA) which are implicated in NDD pathology are still unknown for Lumbricus terrestris, but the three-dimensional (3D) structure of the human counterpart for modeling. AIM: This study aims to generate and evaluate the 3D structure of TrkA, SERT, and AQP proteins and their interaction with the ligands, namely Asiaticoside-D (AD) and levodopa (L-DOPA) the anti-NDD agents. SUBJECTS AND METHODS: Homology modeling for SERT, AQP, and TrkA proteins of Lumbricus terrestris using SWISS-MODEL Server and the modeled structure was validated using Rampage Server. Wet-lab analysis of their correspondent m-RNA levels was also done to validate the in silico data. RESULTS: It was found that TrkA had moderately high homology (67%) to human while SERT and AQP could exhibit 58% and 42%, respectively. The reliability of the model was assessed by Ramachandran plot analysis. Interactions of AD with the SERT, AQP-4, and TrkA showed the binding energies as -9.93, 8.88, and -7.58 of Kcal/mol, respectively, while for L-DOPA did show -3.93, -5.13, and -6.0 Kcal/mol, respectively. The levels of SERT, TrkA, and AQP-4 were significantly reduced (P < 0.001) on ROT induced when compared to those of control worms. On ROT + AD supplementation group (III), m-RNA levels were significantly increased (P < 0.05) when compared to those of ROT induced worms (group II). CONCLUSION: Our pioneering docking data propose the possible of target which is proved useful for therapeutic investigations against the unconquered better of NDD.
Assuntos
Aquaporinas/metabolismo , Levodopa/farmacologia , Modelos Moleculares , Fármacos Neuroprotetores/farmacologia , Receptor trkA/metabolismo , Proteínas da Membrana Plasmática de Transporte de Serotonina/metabolismo , Triterpenos/farmacologia , Animais , Aquaporinas/genética , Gânglios dos Invertebrados/efeitos dos fármacos , Gânglios dos Invertebrados/lesões , Gânglios dos Invertebrados/metabolismo , Oligoquetos , Receptor trkA/genética , Proteínas da Membrana Plasmática de Transporte de Serotonina/genéticaRESUMO
Microcircuit modulation by peptides is well established, but the cellular/synaptic mechanisms whereby identified neurons with identified peptide transmitters modulate microcircuits remain unknown for most systems. Here, we describe the distribution of GYRKPPFNGSIFamide (Gly1-SIFamide) immunoreactivity (Gly1-SIFamide-IR) in the stomatogastric nervous system (STNS) of the crab Cancer borealis and the Gly1-SIFamide actions on the two feeding-related circuits in the stomatogastric ganglion (STG). Gly1-SIFamide-IR localized to somata in the paired commissural ganglia (CoGs), two axons in the nerves connecting each CoG with the STG, and the CoG and STG neuropil. We identified one Gly1-SIFamide-IR projection neuron innervating the STG as the previously identified modulatory commissural neuron 5 (MCN5). Brief (~10 s) MCN5 stimulation excites some pyloric circuit neurons. We now find that bath applying Gly1-SIFamide to the isolated STG also enhanced pyloric rhythm activity and activated an imperfectly coordinated gastric mill rhythm that included unusually prolonged bursts in two circuit neurons [inferior cardiac (IC), lateral posterior gastric (LPG)]. Furthermore, longer duration (>30 s) MCN5 stimulation activated a Gly1-SIFamide-like gastric mill rhythm, including prolonged IC and LPG bursting. The prolonged LPG bursting decreased the coincidence of its activity with neurons to which it is electrically coupled. We also identified local circuit feedback onto the MCN5 axon terminals, which may contribute to some distinctions between the responses to MCN5 stimulation and Gly1-SIFamide application. Thus, MCN5 adds to the few identified projection neurons that modulate a well-defined circuit at least partly via an identified neuropeptide transmitter and provides an opportunity to study peptide regulation of electrical coupled neurons in a functional context. NEW & NOTEWORTHY Limited insight exists regarding how identified peptidergic neurons modulate microcircuits. We show that the modulatory projection neuron modulatory commissural neuron 5 (MCN5) is peptidergic, containing Gly1-SIFamide. MCN5 and Gly1-SIFamide elicit similar output from two well-defined motor circuits. Their distinct actions may result partly from circuit feedback onto the MCN5 axon terminals. Their similar actions include eliciting divergent activity patterns in normally coactive, electrically coupled neurons, providing an opportunity to examine peptide modulation of electrically coupled neurons in a functional context.
Assuntos
Axônios/fisiologia , Gânglios dos Invertebrados/fisiologia , Contração Muscular , Neuropeptídeos/farmacologia , Piloro/inervação , Potenciais de Ação , Animais , Axônios/efeitos dos fármacos , Braquiúros , Retroalimentação Fisiológica , Gânglios dos Invertebrados/citologia , Gânglios dos Invertebrados/efeitos dos fármacos , Periodicidade , Piloro/fisiologiaRESUMO
Long-term but not short-term memory and synaptic plasticity in many brain areas require neurotrophin signaling, transcription, and epigenetic mechanisms including DNA methylation. However, it has been difficult to relate these cellular mechanisms directly to behavior because of the immense complexity of the mammalian brain. To address that problem, we and others have examined numerically simpler systems such as the hermaphroditic marine mollusk Aplysia californica. As a further simplification, we have used a semi-intact preparation of the Aplysia siphon withdrawal reflex in which it is possible to relate cellular plasticity directly to behavioral learning. We find that inhibitors of neurotrophin signaling, transcription, and DNA methylation block sensitization and classical conditioning beginning â¼1 h after the start of training, which is in the time range of an intermediate-term stage of plasticity that combines elements of short- and long-term plasticity and may form a bridge between them. Injection of decitabine (an inhibitor of DNA methylation that may have other actions in these experiments) into an LE sensory neuron blocks the neural correlates of conditioning in the same time range. In addition, we found that both DNA and RNA methylation in the abdominal ganglion are correlated with learning in the same preparations. These results begin to suggest the functions and integration of these different molecular mechanisms during behavioral learning.
Assuntos
Condicionamento Clássico/fisiologia , Metilação de DNA , Memória/fisiologia , Fatores de Crescimento Neural/metabolismo , Plasticidade Neuronal/fisiologia , Transcrição Gênica , Animais , Aplysia , Condicionamento Clássico/efeitos dos fármacos , Metilação de DNA/efeitos dos fármacos , Decitabina/farmacologia , Inibidores Enzimáticos/farmacologia , Gânglios dos Invertebrados/efeitos dos fármacos , Gânglios dos Invertebrados/metabolismo , Memória/efeitos dos fármacos , Microeletrodos , Atividade Motora/efeitos dos fármacos , Atividade Motora/fisiologia , Plasticidade Neuronal/efeitos dos fármacos , RNA/metabolismo , Reflexo/efeitos dos fármacos , Reflexo/fisiologia , Transdução de Sinais/efeitos dos fármacos , Transcrição Gênica/efeitos dos fármacosRESUMO
Multiple neuromodulators act in concert to shape the properties of neural circuits. Different neuromodulators usually activate distinct receptors but can have overlapping targets. Therefore, circuit output depends on neuromodulator interactions at shared targets, a poorly understood process. We explored quantitative rules of co-modulation of two principal targets of neuromodulation: synapses and voltage-gated ionic currents. In the stomatogastric ganglion of the male crab Cancer borealis, the neuropeptides proctolin (Proc) and the crustacean cardioactive peptide (CCAP) modulate synapses of the pyloric circuit and activate a voltage-gated current (IMI) in multiple neurons. We examined the validity of a simple dose-dependent quantitative rule, that co-modulation by Proc and CCAP is predicted by the linear sum of the individual effects of each modulator up to saturation. We found that this rule is valid for co-modulation of synapses, but not for the activation of IMI, in which co-modulation was sublinear. The predictions for the co-modulation of IMI activation were greatly improved if we assumed that the intracellular pathways activated by two peptide receptors inhibit one another. These findings suggest that the pathways activated by two neuromodulators could have distinct interactions, leading to distinct co-modulation rules for different targets even in the same neuron. Given the evolutionary conservation of neuromodulator receptors and signaling pathways, such distinct rules for co-modulation of different targets are likely to be common across neuronal circuits.SIGNIFICANCE STATEMENT We examine the quantitative rules of co-modulation at multiple shared targets, the first such characterization to our knowledge. Our results show that dose-dependent co-modulation of distinct targets in the same cells by the same two neuromodulators follows different rules: co-modulation of synaptic currents is linearly additive up to saturation, whereas co-modulation of the voltage-gated ionic current targeted in a single neuron is nonlinear, a mechanism that is likely generalizable. Given that all neural systems are multiply modulated and neuromodulators often act on shared targets, these findings and the methodology could guide studies to examine dynamic actions of neuromodulators at the biophysical and systems level in sensory and motor functions, sleep/wake regulation, and cognition.
Assuntos
Braquiúros/fisiologia , Neurônios/fisiologia , Neuropeptídeos/fisiologia , Oligopeptídeos/fisiologia , Potenciais Sinápticos , Animais , Geradores de Padrão Central , Gânglios dos Invertebrados/efeitos dos fármacos , Gânglios dos Invertebrados/fisiologia , Masculino , Modelos Neurológicos , Plasticidade Neuronal , Neurônios/efeitos dos fármacos , Neuropeptídeos/administração & dosagem , Oligopeptídeos/administração & dosagemRESUMO
Many animals depend on descending information from the brain for the initiation and proper execution of locomotion. Interestingly, after injury and the loss of such inputs, locomotor function can sometimes be regained without the regrowth of central connections. In the medicinal leech, Hirudo verbana, we have shown that crawling reemerges after removal of descending inputs. Here, we studied the mechanisms underlying this return of locomotion by asking if central pattern generators (CPGs) in crawl-recovered leeches are sufficient to produce crawl-specific intersegmental coordination. From recovered animals, we treated isolated chains of ganglia with dopamine to activate the crawl CPGs (one crawl CPG per ganglion) and observed fictive crawl-like bursting in the dorsal-longitudinal-excitor motoneuron (DE-3), an established crawl-monitor neuron. However, these preparations did not exhibit crawl-specific coordination across the CPGs. Although the crawl CPGs always generated bidirectional activation of adjacent CPGs, we never observed crawl-appropriate intersegmental phase delays. Because central circuits alone were unable to organize crawl-specific coordination, we tested the coordinating role of the peripheral nervous system. In transected leeches normally destined for recovery, we removed afferent information to the anterior-most (lead) ganglion located below the nerve-cord transection site. In these dually treated animals, overt crawling was greatly delayed or prevented. After filling the peripheral nerves with Neurobiotin tracer distal to the nerve-root lesion, we found a perfect correlation between regrowth of peripheral neuronal fibers and crawl recovery. Our study establishes that during recovery after injury, crawl-specific intersegmental coordination switches to a new dependence on afferent information.
Assuntos
Geradores de Padrão Central/fisiologia , Dopamina/farmacologia , Gânglios dos Invertebrados/fisiologia , Locomoção/fisiologia , Neurônios Motores/fisiologia , Plasticidade Neuronal/fisiologia , Propriocepção/fisiologia , Recuperação de Função Fisiológica/fisiologia , Animais , Gânglios dos Invertebrados/efeitos dos fármacos , Gânglios dos Invertebrados/lesões , Hirudo medicinalis , Recuperação de Função Fisiológica/efeitos dos fármacosRESUMO
A learning experience may lead to changes in behavior during the experience, and also to memory expressed at a later time. Are signals causing changes in behavior during the learning experience related to the formation and expression of memory? We examined this question, using learning that food is inedible in Aplysia Treatment of an isolated buccal ganglia preparation with an NO donor elicited rejection-like motor programs. Rejection initiated by NO production is consistent with aspects of behavioral changes seen while animals learn, and with memory formation. Nonetheless, applying the NO donor during training had only minor effects on behavior during the training, and did not improve memory, indicating that the induction of rejection in the buccal ganglia is unlikely to be the means by which NO during training contributes to memory formation. Block of NO during memory retrieval prevented the expression of memory, as measured by a lack of savings in time to stop responding to food. Applying an NO donor to the cerebral ganglion while eliciting fictive feeding inhibited the expression of feeding activity, indicating that some NO effects on memory consolidation and on expression of memory may be via effects on the cerebral ganglion.
Assuntos
Aplysia/fisiologia , Comportamento Alimentar , Gânglios dos Invertebrados/fisiologia , Memória/fisiologia , Óxido Nítrico/fisiologia , Animais , Gânglios dos Invertebrados/efeitos dos fármacos , Memória/efeitos dos fármacos , Atividade Motora/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Óxido Nítrico/administração & dosagemRESUMO
Training Aplysia with inedible food for a period that is too brief to produce long-term memory becomes effective in producing memory when training is paired with a nitric oxide (NO) donor. Lip stimulation for the same period of time paired with an NO donor is ineffective. Using qPCR, we examined molecular correlates of brief training versus lip stimulation, of treatment with an NO donor versus saline, and of the combined stimuli producing long-term memory. Changes were examined in mRNA expression of Aplysia homologs of C/EBP, CREB1, CREB1α, CREB1ß, and CREB2, in both the buccal and cerebral ganglia controlling feeding. Both the brief training and the NO donor increased expression of C/EBP, CREB1, CREB1α, and CREB1ß, but not CREB2 in the buccal ganglia. For CREB1α, there was a significant interaction between the effects of the brief training and of the NO donor. In addition, the NO donor, but not brief training, increased expression of all of the genes in the cerebral ganglion. These findings show that the components of learning that alone do not produce memory produce molecular changes in different ganglia. Thus, long-term memory is likely to arise by both additive and interactive increases in gene expression.
Assuntos
Comportamento Alimentar/fisiologia , Comportamento Alimentar/psicologia , Gânglios dos Invertebrados/metabolismo , Aprendizagem/fisiologia , Memória de Longo Prazo/fisiologia , Animais , Aplysia , Comportamento Alimentar/efeitos dos fármacos , Gânglios dos Invertebrados/efeitos dos fármacos , Expressão Gênica/efeitos dos fármacos , Aprendizagem/efeitos dos fármacos , Memória de Longo Prazo/efeitos dos fármacos , Proteínas do Tecido Nervoso/metabolismo , Doadores de Óxido Nítrico/farmacologia , S-Nitroso-N-Acetilpenicilamina/farmacologiaRESUMO
The chemical agent sulfur mustard (SM) causes erythema, skin blisters, ulcerations, and delayed wound healing. It is accepted that the underlying molecular toxicology is based on DNA alkylation. With an expected delay, DNA damage causes impairment of protein biosynthesis and disturbance of cell division. However, using the cockroach model Blaptica dubia, the presented results show that alkylating compounds provoke immediate behavior responses along with fast changes in the electrical field potential (EFP) of neurons, suggesting that lesions of DNA are probably not the only effect of alkylating compounds. Blaptica dubia was challenged with SM or 2-chloroethyl-ethyl sulfide (CEES). Acute toxicity was objectified by a disability score. Physiological behavior responses (antennae pullback reflex, escape attempts, and grooming) were monitored after exposure. To estimate the impact of alkylating agents on neuronal activity, EFP recordings of the antennae and the thoracic ganglion were performed. After contact to neat SM, a pullback reflex of the antennae was the first observation. Subsequently, a striking escape behavior occured which was characterized by persistent movement of the legs. In addition, an instantaneous processing of the electrical firing pattern from the antennae to the descending ganglia was detectable. Remarkably, comparing the toxicity of the applied alkylating agents, effects induced by CEES were much more pronounced compared to SM. In summary, our findings document immediate effects of B. dubia after exposure to alkylating substances. These fast responses cannot be interpreted as a consequence of DNA alkylation. Therefore, the dogma that DNA alkylation is the exclusive cause for SM toxicity has to be questioned.
Assuntos
Antenas de Artrópodes/efeitos dos fármacos , Baratas/efeitos dos fármacos , Baratas/fisiologia , Gás de Mostarda/análogos & derivados , Gás de Mostarda/toxicidade , Alquilantes/toxicidade , Animais , Antenas de Artrópodes/fisiologia , Comportamento Animal/efeitos dos fármacos , Substâncias para a Guerra Química/toxicidade , Relação Dose-Resposta a Droga , Eletrofisiologia/métodos , Extremidades , Voo Animal/efeitos dos fármacos , Gânglios dos Invertebrados/efeitos dos fármacos , Gânglios dos Invertebrados/metabolismo , Gás de Mostarda/administração & dosagemRESUMO
We describe a sequence of experiments performed in vitro to verify the existence of a new magnetic resonance imaging contrast - Magnetic Resonance Electrical Impedance Tomography (MREIT) -sensitive to changes in active membrane conductivity. We compared standard deviations in MREIT phase data from spontaneously active Aplysia abdominal ganglia in an artificial seawater background solution (ASW) with those found after treatment with an excitotoxic solution (KCl). We found significant increases in MREIT treatment cases, compared to control ganglia subject to extra ASW. This distinction was not found in phase images from the same ganglia using no imaging current. Further, significance and effect size depended on the amplitude of MREIT imaging current used. We conclude that our observations were linked to changes in cell conductivity caused by activity. Functional MREIT may have promise as a more direct method of functional neuroimaging than existing methods that image correlates of blood flow such as BOLD fMRI.
Assuntos
Potenciais de Ação/fisiologia , Impedância Elétrica , Gânglios dos Invertebrados/diagnóstico por imagem , Imageamento por Ressonância Magnética/métodos , Neurônios/fisiologia , Potenciais de Ação/efeitos dos fármacos , Animais , Aplysia , Butiratos/farmacologia , Gânglios dos Invertebrados/efeitos dos fármacos , Hidrocarbonetos Fluorados/farmacologia , Técnicas In Vitro , Neurônios/efeitos dos fármacos , Neurotoxinas/farmacologiaRESUMO
To efficiently move around, animals need to coordinate their limbs. Proper, context-dependent coupling among the neural networks underlying leg movement is necessary for generating intersegmental coordination. In the slow-walking stick insect, local sensory information is very important for shaping coordination. However, central coupling mechanisms among segmental central pattern generators (CPGs) may also contribute to this. Here, we analyzed the interactions between contralateral networks that drive the depressor trochanteris muscle of the legs in both isolated and interconnected deafferented thoracic ganglia of the stick insect on application of pilocarpine, a muscarinic acetylcholine receptor agonist. Our results show that depressor CPG activity is only weakly coupled between all segments. Intrasegmental phase relationships differ between the three isolated ganglia, and they are modified and stabilized when ganglia are interconnected. However, the coordination patterns that emerge do not resemble those observed during walking. Our findings are in line with recent studies and highlight the influence of sensory input on coordination in slowly walking insects. Finally, as a direct interaction between depressor CPG networks and contralateral motoneurons could not be observed, we hypothesize that coupling is based on interactions at the level of CPG interneurons.NEW & NOTEWORTHY Maintaining functional interleg coordination is vitally important as animals locomote through changing environments. The relative importance of central mechanisms vs. sensory feedback in this process is not well understood. We analyzed coordination among the neural networks generating leg movements in stick insect preparations lacking phasic sensory feedback. Under these conditions, the networks governing different legs were only weakly coupled. In stick insect, central connections alone are thus insufficient to produce the leg coordination observed behaviorally.
Assuntos
Gânglios dos Invertebrados/fisiologia , Insetos/fisiologia , Interneurônios/fisiologia , Neurônios Motores/fisiologia , Agonistas Muscarínicos/farmacologia , Rede Nervosa/fisiologia , Caminhada/fisiologia , Animais , Feminino , Gânglios dos Invertebrados/efeitos dos fármacos , Insetos/efeitos dos fármacos , Interneurônios/efeitos dos fármacos , Neurônios Motores/efeitos dos fármacos , Rede Nervosa/efeitos dos fármacos , Pilocarpina/farmacologiaRESUMO
The neuromodulator-gated current (IMI) found in the crab stomatogastric ganglion is activated by neuromodulators that are essential to induce the rhythmic activity of the pyloric network in this system. One of these neuromodulators is also known to control the correlated expression of voltage-gated ionic currents in pyloric neurons, as well as synaptic plasticity and strength. Thus understanding the mechanism by which neuromodulator receptors activate IMI should provide insights not only into how oscillations are initiated but also into how other processes, and currents not directly activated by them, are regulated. To determine what specific signaling molecules are implicated in this process, we used a battery of agonists and antagonists of common signal transduction pathways. We found that the G protein inhibitor GDPßS and the G protein activator GTPγS significantly affect IMI amplitude, suggesting that its activation is mediated by G proteins. Interestingly, when using the more specific G protein blocker pertussis toxin, we observed the expected inhibition of IMI amplitude but, unexpectedly, in a calcium-dependent fashion. We also found that antagonists of calcium- and calmodulin-associated signaling significantly reduce IMI amplitude. In contrast, we found little evidence for the role of cyclic nucleotide signaling, phospholipase C (PLC), or kinases and phosphatases, except two calmodulin-dependent kinases. In sum, these results suggest that proctolin-induced IMI is mediated by a G protein whose pertussis toxin sensitivity is altered by external calcium concentration and appears to depend on intracellular calcium, calmodulin, and calmodulin-activated kinases. In contrast, we found no support for IMI being mediated by PLC signaling or cyclic nucleotides.NEW & NOTEWORTHY Neuronal rhythmic activity is generated by either network-based or cell-autonomous mechanisms. In the pyloric network of decapod crustaceans, the activation of a neuromodulator-gated pacemaker current is crucial for the generation of rhythmic activity. This current is activated by several neuromodulators, including peptides and acetylcholine, presumably via metabotropic receptors. We have previously demonstrated a novel extracellular calcium-sensitive voltage-dependence mechanism of this current. We presently report that the activation mechanism depends on intracellular and extracellular calcium-sensitive components.
Assuntos
Relógios Biológicos/fisiologia , Gânglios dos Invertebrados/metabolismo , Canais Iônicos/metabolismo , Neurônios/metabolismo , Animais , Relógios Biológicos/efeitos dos fármacos , Braquiúros , Sistema Nervoso Entérico/efeitos dos fármacos , Sistema Nervoso Entérico/metabolismo , Gânglios dos Invertebrados/efeitos dos fármacos , Íons/metabolismo , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Microeletrodos , Neurônios/efeitos dos fármacos , Neurotransmissores/farmacologia , Técnicas de Cultura de TecidosRESUMO
The pond snail Lymnaea stagnalis is reported to be anoxia-tolerant and if the tolerance mechanism is similar to that of the anoxia-tolerant painted turtle, GABA should play an important role. A potentially confounding factor investigating the role of GABA in anoxia tolerance are reports that GABA has both inhibitory and excitatory effects within L. stagnalis central ganglion. We therefore set out to determine if seasonality or photoperiod has an impact on: 1) the anoxia-tolerance of the intact pond snail, and 2) the response of isolated neuroganglia cluster F neurons to exogenous GABA application. L. stagnalis maintained on a natural summer light cycle were unable to survive any period of anoxic exposure, while those maintained on a natural winter light cycle survived a maximum of 4h. Using intracellular sharp electrode recordings from pedal ganglia cluster F neurons we show that there is a photoperiod dependent shift in the response to GABA. Snails exposed to a 16h:8h light:dark cycle in an environmental chamber (induced summer phenotype) exhibited hyperpolarizing inhibitory responses and those exposed to a 8h:16h light:dark cycle (induced winter phenotype) exhibited depolarizing excitatory responses to GABA application. Using gramicidin-perforated patch recordings we also found a photoperiod dependent shift in the reversal potential for GABA. We conclude that the opposing responses of L. stagnalis central neurons to GABA results from a shift in intracellular chloride concentration that is photoperiod dependent and is likely mediated through the relative efficacy of cation chloride co-transporters. Although the physiological ramifications of the photoperiod dependent shift are unknown this work potentially has important implications for the impact of artificial light pollution on animal health.