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Sheng Li Xue Bao : [Acta Physiologica... Aug 2017Improvements in the imaging of neural circuits are essential for studies of network function in both invertebrates and vertebrates. Therefore, CLARITY, a new imaging...
Improvements in the imaging of neural circuits are essential for studies of network function in both invertebrates and vertebrates. Therefore, CLARITY, a new imaging enhancement technique developed for mouse brains has attracted broad interest from researchers working on other species. We studied the potential of a modified version of CLARITY to enhance the imaging of ganglia in an invertebrate Aplysia. For example, we have modified the hydrogel solution and designed a small container for the Aplysia ganglia. The ganglia were first processed for immunohistochemistry, and then for CLARITY. We examined the compatibility of these techniques and the extent to which the imaging of fluorescence improved using confocal microscopy. We found that CLARITY did indeed enhance the imaging of CP2 immunopositive neurons in Aplysia ganglia. For example, it improved visualization of small, weak immunoreactive neurons deep in the ganglia. Our modifications of CLARITY make this new method suitable for future use in Aplysia experiments. Furthermore, our techniques are likely to facilitate imaging in other invertebrate ganglia.
Topics: Animals; Aplysia; Ganglia, Invertebrate; Image Enhancement; Immunohistochemistry; Neurons
PubMed: 28825105
DOI: No ID Found -
Progress in Brain Research 1994
Comparative Study Review
Topics: Aging; Animals; Aplysia; Learning; Nervous System; Nervous System Physiological Phenomena; Neuronal Plasticity
PubMed: 7938517
DOI: 10.1016/s0079-6123(08)60784-0 -
Journal of Neurophysiology May 2023Many behaviors and types of information storage are mediated by lengthy changes in neuronal activity. In bag cell neurons of the hermaphroditic sea snail , a transient...
Many behaviors and types of information storage are mediated by lengthy changes in neuronal activity. In bag cell neurons of the hermaphroditic sea snail , a transient cholinergic synaptic input triggers an ∼30-min afterdischarge. This causes these neuroendocrine cells to release egg laying hormone and elicit reproductive behavior. When acetylcholine is pressure-ejected onto a current-clamped bag cell neuron, the evoked depolarization is far longer than the current evoked by acetylcholine under voltage clamp, suggesting recruitment of another conductance. Our earlier studies found bag cell neurons to display a voltage-dependent persistent Ca current. Hence, we hypothesized that this current is activated by the acetylcholine-induced depolarization and sought a selective Ca current blocker. Rapid Ca current evoked by 200-ms depolarizing steps in voltage-clamped cultured bag cell neurons demonstrated a concentration-dependent sensitivity to Ni, Co, Zn, and verapamil but not Cd or ω-conotoxin GIVa. Leak subtraction of Ca current evoked by 10-s depolarizing steps using the IC (concentration required to eliminate maximal current) of Ni, Co, Zn, or verapamil revealed persistent Ca current, demonstrating persistent current block. Only Co and Zn did not suppress the acetylcholine-induced current, although Zn appeared to impact additional channels. When Co was applied during an acetylcholine-induced depolarization, the amplitude was reduced; furthermore, protein kinase C activation, previously established to enhance the persistent Ca current, extended the depolarization. Therefore, the persistent Ca current sustains the acetylcholine-induced depolarization and may translate brief cholinergic input into afterdischarge initiation. This could be a general mechanism of triggering long-term change in activity with a short-lived input. Ionotropic acetylcholine receptors mediate brief synaptic communication, including in bag cell neurons of the sea snail . However, this study demonstrates that cholinergic depolarization can open a voltage-gated persistent Ca current, which extends the bag cell neuron response to acetylcholine. Bursting in these neuroendocrine cells results in hormone release and egg laying. Thus, this emphasizes the role of ionotropic signaling in reaching a depolarized level to engage Ca influx and perpetuating the activity necessary for behavior.
Topics: Animals; Aplysia; Acetylcholine; Neurons; Cholinergic Agents; Verapamil; Hormones; Calcium
PubMed: 36988203
DOI: 10.1152/jn.00429.2022 -
Biological Cybernetics Dec 2020Animals exhibit remarkable feats of behavioral flexibility and multifunctional control that remain challenging for robotic systems. The neural and morphological basis of...
Animals exhibit remarkable feats of behavioral flexibility and multifunctional control that remain challenging for robotic systems. The neural and morphological basis of multifunctionality in animals can provide a source of bioinspiration for robotic controllers. However, many existing approaches to modeling biological neural networks rely on computationally expensive models and tend to focus solely on the nervous system, often neglecting the biomechanics of the periphery. As a consequence, while these models are excellent tools for neuroscience, they fail to predict functional behavior in real time, which is a critical capability for robotic control. To meet the need for real-time multifunctional control, we have developed a hybrid Boolean model framework capable of modeling neural bursting activity and simple biomechanics at speeds faster than real time. Using this approach, we present a multifunctional model of Aplysia californica feeding that qualitatively reproduces three key feeding behaviors (biting, swallowing, and rejection), demonstrates behavioral switching in response to external sensory cues, and incorporates both known neural connectivity and a simple bioinspired mechanical model of the feeding apparatus. We demonstrate that the model can be used for formulating testable hypotheses and discuss the implications of this approach for robotic control and neuroscience.
Topics: Animals; Aplysia; Biomechanical Phenomena; Deglutition; Feeding Behavior
PubMed: 33301053
DOI: 10.1007/s00422-020-00851-9 -
Biological Cybernetics Feb 2017Motor systems must adapt to perturbations and changing conditions both within and outside the body. We refer to the ability of a system to maintain performance despite...
Motor systems must adapt to perturbations and changing conditions both within and outside the body. We refer to the ability of a system to maintain performance despite perturbations as "robustness," and the ability of a system to deploy alternative strategies that improve fitness as "flexibility." Different classes of pattern-generating circuits yield dynamics with differential sensitivities to perturbations and parameter variation. Depending on the task and the type of perturbation, high sensitivity can either facilitate or hinder robustness and flexibility. Here we explore the role of multiple coexisting oscillatory modes and sensory feedback in allowing multiphasic motor pattern generation to be both robust and flexible. As a concrete example, we focus on a nominal neuromechanical model of triphasic motor patterns in the feeding apparatus of the marine mollusk Aplysia californica. We find that the model can operate within two distinct oscillatory modes and that the system exhibits bistability between the two. In the "heteroclinic mode," higher sensitivity makes the system more robust to changing mechanical loads, but less robust to internal parameter variations. In the "limit cycle mode," lower sensitivity makes the system more robust to changes in internal parameter values, but less robust to changes in mechanical load. Finally, we show that overall performance on a variable feeding task is improved when the system can flexibly transition between oscillatory modes in response to the changing demands of the task. Thus, our results suggest that the interplay of sensory feedback and multiple oscillatory modes can allow motor systems to be both robust and flexible in a variable environment.
Topics: Animals; Aplysia; Feedback, Sensory; Motor Activity
PubMed: 28004255
DOI: 10.1007/s00422-016-0704-8 -
BMC Biology Mar 2021Amyloids are ordered, insoluble protein aggregates, characterized by a cross-β sheet quaternary structure in which molecules in a β-strand conformation are stacked...
BACKGROUND
Amyloids are ordered, insoluble protein aggregates, characterized by a cross-β sheet quaternary structure in which molecules in a β-strand conformation are stacked along the filament axis via intermolecular interactions. While amyloids are typically associated with pathological conditions, functional amyloids have also been identified and are present in a wide variety of organisms ranging from bacteria to humans. The cytoplasmic polyadenylation element-binding (CPEB) prion-like protein is an mRNA-binding translation regulator, whose neuronal isoforms undergo activity-dependent aggregation, a process that has emerged as a plausible biochemical substrate for memory maintenance. CPEB aggregation is driven by prion-like domains (PLD) that are divergent in sequence across species, and it remains unknown whether such divergent PLDs follow a similar aggregating assembly pathway. Here, we describe the amyloid-like features of the neuronal Aplysia CPEB (ApCPEB) PLD and compare them to those of the Drosophila ortholog, Orb2 PLD.
RESULTS
Using in vitro single-molecule and bulk biophysical methods, we find transient oligomers and mature amyloid-like filaments that suggest similarities in the late stages of the assembly pathway for both ApCPEB and Orb2 PLDs. However, while prior to aggregation the Orb2 PLD monomer remains mainly as a random coil in solution, ApCPEB PLD adopts a diversity of conformations comprising α-helical structures that evolve to coiled-coil species, indicating structural differences at the beginning of their amyloid assembly pathways.
CONCLUSION
Our results indicate that divergent PLDs of CPEB proteins from different species retain the ability to form a generic amyloid-like fold through different assembly mechanisms.
Topics: Amyloid; Animals; Aplysia; Polyadenylation; Prions
PubMed: 33706787
DOI: 10.1186/s12915-021-00967-9 -
Journal of Visualized Experiments : JoVE Jul 2012It has been suggested that changes in intracellular calcium mediate the induction of a number of important forms of synaptic plasticity (e.g., homosynaptic...
It has been suggested that changes in intracellular calcium mediate the induction of a number of important forms of synaptic plasticity (e.g., homosynaptic facilitation). These hypotheses can be tested by simultaneously monitoring changes in intracellular calcium and alterations in synaptic efficacy. We demonstrate how this can be accomplished by combining calcium imaging with intracellular recording techniques. Our experiments are conducted in a buccal ganglion of the mollusc Aplysia californica. This preparation has a number of experimentally advantageous features: Ganglia can be easily removed from Aplysia and experiments use adult neurons that make normal synaptic connections and have a normal ion channel distribution. Due to the low metabolic rate of the animal and the relatively low temperatures (14-16 °C) that are natural for Aplysia, preparations are stable for long periods of time. To detect changes in intracellular free calcium we will use the cell impermeant version of Calcium Orange which is easily 'loaded' into a neuron via iontophoresis. When this long wavelength fluorescent dye binds to calcium, fluorescence intensity increases. Calcium Orange has fast kinetic properties and, unlike ratiometric dyes (e.g., Fura 2), requires no filter wheel for imaging. It is fairly photo stable and less phototoxic than other dyes (e.g., fluo-3). Like all non-ratiometric dyes, Calcium Orange indicates relative changes in calcium concentration. But, because it is not possible to account for changes in dye concentration due to loading and diffusion, it can not be calibrated to provide absolute calcium concentrations. An upright, fixed stage, compound microscope was used to image neurons with a CCD camera capable of recording around 30 frames per second. In Aplysia this temporal resolution is more than adequate to detect even a single spike induced alteration in the intracellular calcium concentration. Sharp electrodes are simultaneously used to induce and record synaptic transmission in identified pre- and postsynaptic neurons. At the conclusion of each trial, a custom script combines electrophysiology and imaging data. To ensure proper synchronization we use a light pulse from a LED mounted in the camera port of the microscope. Manipulation of presynaptic calcium levels (e.g. via intracellular EGTA injection) allows us to test specific hypotheses, concerning the role of intracellular calcium in mediating various forms of plasticity.
Topics: Animals; Aplysia; Calcium; Chromosome Pairing; Electrophysiology; Fluorescent Dyes; Microscopy, Fluorescence; Models, Animal; Neurons; Organic Chemicals
PubMed: 22824826
DOI: 10.3791/3907 -
Molecules and Cells Apr 2003Brain-derived neurotrophic factor (BDNF) plays a key role in the differentiation and neuritogenesis of developing neurons, and in the synaptic plasticity of mature...
Brain-derived neurotrophic factor (BDNF) plays a key role in the differentiation and neuritogenesis of developing neurons, and in the synaptic plasticity of mature neurons, in the mammalian nervous system. BDNF binds to the receptor tyrosine kinase TrkB and transmits neurotrophic signals by activating neuron-specific tyrosine phosphorylation pathways. However, the neurotrophic function of BDNF in Aplysia neurons is poorly understood. We examined the specific effect of BDNF on neurite outgrowth and synaptic plasticity in cultured Aplysia neurons and a multipotent rat hippocampal stem cell line (HiB5). Our study indicates that mammalian BDNF has no significant effect on the neuritogenesis, neurotransmitter release, excitability, and synaptic plasticity of cultured Aplysia neurons in our experimental conditions. In contrast, BDNF in combination with platelet-derived growth factor (PDGF) increases the length of the neurites and the number of spine-like structures in cells of HiB5.
Topics: Animals; Aplysia; Brain-Derived Neurotrophic Factor; Cell Line; Hippocampus; Mammals; Neurons; Synapses
PubMed: 12803487
DOI: No ID Found -
Progress in Brain Research 1994
Review
Topics: Actins; Animals; Aplysia; Axons; Cell Adhesion; Extracellular Matrix; Genistein; Hemolymph; Isoflavones; Nerve Growth Factors; Nerve Tissue Proteins; Neurites; Phosphorylation; Protein Processing, Post-Translational; Receptor Protein-Tyrosine Kinases; Receptors, Nerve Growth Factor; Signal Transduction
PubMed: 7886223
DOI: 10.1016/s0079-6123(08)61128-0 -
Learning & Memory (Cold Spring Harbor,... Jul 2021Most studies of molecular mechanisms of synaptic plasticity have focused on the sequence of changes either at individual synapses or in the cell nucleus. However,...
Most studies of molecular mechanisms of synaptic plasticity have focused on the sequence of changes either at individual synapses or in the cell nucleus. However, studies of long-term facilitation at sensory neuron-motor neuron synapses in isolated cell culture suggest two additional features of facilitation. First, that there is also regulation of the number of synaptic contacts between two neurons, which may occur at the level of cell pair-specific branch points in the neuronal arbor. Branch points contain many molecules that are involved in protein synthesis-dependent long-term facilitation including neurotrophins and the RNA binding protein CPEB. Second, the regulation involves homeostatic feedback and tends to keep the total number of contacts between two neurons at a fairly constant level both at rest and following facilitation. That raises the question of how facilitation and homeostasis can coexist. A possible answer is suggested by the findings that they both involve spontaneous transmission and postsynaptic Ca, which can have bidirectional effects similar to LTP and LTD in hippocampus. In addition, long-term facilitation can involve a change in the set point of homeostasis, which could be encoded by plasticity molecules such as CPEB and/or PKM. A computational model based on these ideas can qualitatively simulate the basic features of both facilitation and homeostasis of the number of contacts.
Topics: Animals; Aplysia; Homeostasis; Models, Biological; Neuronal Plasticity; Neurons
PubMed: 34131053
DOI: 10.1101/lm.053124.120