Influence of mRNA and protein synthesis inhibitors on the long-term memory acquisition of classically conditioned earthworms

Stretchable elastic synaptic transistors for neurologically integrated soft engineering systems

Artificial synaptic devices that can be stretched similar to those appearing in soft-bodied animals, such as earthworms, could be seamlessly integrated onto soft machines toward enabled neurological functions. Here, we report a stretchable synaptic transistor fully based on elastomeric electronic materials, which exhibits a full set of synaptic characteristics. These characteristics retained even the rubbery synapse that is stretched by 50%. By implementing stretchable synaptic transistor with mechanoreceptor in an array format, we developed a deformable sensory skin, where the mechanoreceptors interface the external stimulations and generate presynaptic pulses and then the synaptic transistors render postsynaptic potentials. Furthermore, we demonstrated a soft adaptive neurorobot that is able to perform adaptive locomotion based on robotic memory in a programmable manner upon physically tapping the skin. Our rubbery synaptic transistor and neurologically integrated devices pave the way toward enabled neurological functions in soft machines and other applications.

Proteins or RNA synthesis inhibitors suppressed induction of amnesia developing under impairment of memory reconsolidation by serotonin receptors antagonist

Studies have shown that retrieval of long-term memory can cause memory reconsolidation, and impaired reconsolidation leads to amnesia development. However, the mechanisms of amnesia induction due to impaired memory reconsolidation remains poorly described. Using experiments involving grape snails trained to conditioned food aversion, we studied the role of translation and transcription processes and the role of serotonin receptors in the mechanisms of amnesia induction. We found that administration of a serotonin receptor antagonist or a protein synthesis inhibitor before the administration of a reminder using a conditioned food stimulus induced amnesia development, whereas injections of mRNA synthesis inhibitor did not affect memory safety. Moreover, combined injections of an antagonist of serotonin receptor and inhibitors of protein or mRNA synthesis before reminder administration completely prevented amnesia development. In addition, inhibitors of protein or mRNA synthesis prevented amnesia development 3 h but not 9 h after the administration of a serotonin receptor antagonist/reminder. We hypothesize that the mechanisms of amnesia induction caused by impaired memory reconsolidation depend on protein and mRNA syntheses within a certain time window, similar to the mechanisms of induction of other long-term plastic brain rearrangements.

Classical conditioning in earthworms employing an odorous conditioned stimulus

The study of associative learning in invertebrates has become an essential tool for exploring their cognitive abilities and for studying the biological bases of learning and memory. In this experiment with earthworms, we paired a rose odour conditioned stimulus (CS) with a bright light unconditioned stimulus (US). After these pairings, the head retraction response - which is initially elicited by the bright light - is eventually evoked by the rose odour. This is the first demonstration of classical conditioning of an odour in earthworms (vibrations are usually employed as CSs), using a procedure that enables us to rule out an explanation in terms of pseudoconditioning.

The novel phytocomponent asiaticoside-D isolated from Centella asiatica exhibits monoamine oxidase-B inhibiting potential in the rotenone degenerated cerebral ganglions of Lumbricus terrestris

BACKGROUND

Centella asiatica (CA) is one of the most valuable herbal medicines widely being used for the treatment of various neurological ailments that are challenging for health-care providers and also is deemed to be safe and effective.

PURPOSE

Monoamines (MAs) are neurotransmitters and neuromodulators that play a significant role in the neural communication, regulation of motor and cognitive functions in the brain. Neurodegeneration is associated with elevated levels of MAO-B that can lead to damaging reactive oxygen species (ROS) in the brain. The current study, evaluated the effects of asiaticoside-D (AD) from neuroprotective CA, on the levels and activities of monoamine oxidase A and B (MAO-A and B), in addition to the behavioral analysis.

METHODS

Qualitative and quantitative analyses of various solvent extracts of CA were performed. The extracts were screened for antioxidant potential using 1,1-diphenyl-2-picryl hydroxyl (DPPH), 2,2'-azinobis-3-ethylbenzothiozoline-6-sulfonic acid (ABTS), hydrogen peroxide (H₂O₂) radical, nitric oxide (NO) radical inhibition, lipid peroxidation (LPO) and ferric reducing antioxidant power (FRAP) assays. The purification of AD was done by column, thin layer and high-performance liquid chromatographies followed by structural elucidation using IR, HR-MS, ¹H and ¹³C NMR spectra. Docking studies were performed to assess the impact of AD on MAO-A and B.In vivo, Lumbricus terrestris were exposed to 0.4 ppm rotenone (ROT) of medium for 7 days and were subjected to co-treatment along with 15 ppm of AD from CA. At the end of experiment period, the neuronal behavior of worms was assessed. Cerebral ganglions (CGs) were removed and the m-RNA levels of MAO-A and B were analyzed by Semi Q-PCR and their activities were also analyzed.

RESULTS

The ethanolic extracts exhibited higher antiradical activity against DPPH, ABTS, H₂O₂, LPO, FRAP, NO and vitamin C with EC₅₀ value of 20.2, 20.9, 20.4, 22.0, 24.9, 28.1, 25.5 and 22.0 µg/ml respectively. Structural analysis by IR, HR-MS, ¹H and ¹³C NMR spectrum have shown the structure of the isolated compound as (2α, 3β)-2,3-dihydroxyurs-12-en-28-oicacid-O-α-L-rhamnopyranosyl-(1→4)-O-β-d-glucopyranosyl (1→6)-β-copyranosyl ester and was represented as AD. In silico interaction of AD with MAO-A and B residues Lys312 at distances of 1.84 Å and 2.44 Å respectively was found to exhibit high binding energy of -9.4 and 7.4 kcal. The neuronal behavior using L. terrestris showed significant improvement against (p < 0.001) ROT impaired behavior (group II) on AD supplementation (p < 0.05). Further, the m-RNA levels and activities of MAO-A and B which were significantly altered (p < 0.001) by ROT could be effectively maintained on AD supplementation.

CONCLUSION

AD was found to exert its negative impact on the levels and activities of MAO-A and B in CGs of rotenone- induced changes in L. terrestris, the property which is considered to be crucial against ROT induced neurodegenerative pathology like -Parkinsonism.

Aberrant neurotransmissional mRNAs in cerebral ganglions of rotenone-exposed Lumbricus terrestris exhibiting motor dysfunction and altered cognitive behavior

Rotenone (ROT) was shown to affect cerebral ganglions (CGs) of Lumbricus terrestris as a pioneering observation in our earlier investigation. Though ROT is a well-known neurotoxin causing neurodegeneration (ND), the precipitation of movement dysfunction remains largely unknown. We have designed the current study to analyze motor abnormalities in worms by exposing them to different concentrations (0.0-0.4 ppm) of ROT for 7 days. GABA, cholinergic receptor, serotonin transporter (SERT), acetylcholine esterase (AchE), and dopamine-β-hydroxylase that are well known for their involvement in neuromuscular junctions were investigated by qRT-PCR. Further, neuronal mitochondrial genes (cytochrome C oxidase-2, NADH deydrogenase-1, cytochrome-b) and actin-1 that are essential for regeneration and calreticulin (phagocytosis) were investigated. The levels of neurotransmitters, lipids, ATPase, neuronal behavior analyses, and fluorescence analysis (lipid droplets) were performed in CGs which showed significant variations at 0.3 ppm. Ultrastructural changes in lipid droplet and neuromelatonin were prominent in 0.3 ppm. Dose-dependent effect of ROT on behavior alteration and expression of m-RNAs studied suggested that at 0.3 ppm, it could deteriorate motor and cognitive functions. We predict that perhaps, by virtue of its effect on cerebral ganglionic genes and their neurotransmitting potential, ROT may cause morbidities that resemble features characteristic of hemiparkinsonic degeneration.

Protein synthesis inhibitors induce both memory impairment and its recovery

The involvement of protein synthesis in the mechanisms of conditioned food aversion memory impairment and recovery in grape snails was studied. It was found that protein synthesis inhibitor (cycloheximide) injections before a reminder by the conditioned stimulus (CS) caused amnesia development. Three days after amnesia induction, injections of cycloheximide or another protein synthesis inhibitor, anisomycin, combined with a reminder by four CSs resulted in memory retrieval, which was saved for 24 h. Cycloheximide injections and the administration of one CS as a reminder to an amnestic animals caused the memory expression only in response to this CS, while it was absent the next day. The isolated administration of a reminder or inhibitor injections without a reminder was not effective. It is suggested that amnesia is an active process and that one of its mechanisms may be a protein-dependent amnesia reactivation caused by a reminder. The administration of protein synthesis inhibitors led to impairment of amnesia reactivation and to recovery of the state formed before amnesia induction and thus to the recovery of conditioned food aversion memory.

Earthworm individualities when facing a conflict between turn alternation and aversive learning

An individual’s personality develops through a combination of experiences and parental inheritance. When faced with a conflict, will an individual take an innate behavior or a learned one? In such situations, individuality will manifest itself. Here, we focused on turn alternation behavior, which is a habitual tendency to turn in the direction opposite the preceding turn, in earthworms (Eisenia fetida) and examined how this behavior is affected by an aversive stimulus. Of 10 earthworms, 3 were affected by the stimulus. Turn alternation deteriorated in two worms, one of which showed anti-turn alternation behavior, whereas the remaining worm showed an enhanced tendency toward turn alternation. Earthworms have a relatively simple nervous system. This study opens the door to investigate the neuronal basis for individuality that emerges between nature and nurture.

Immediate and persistent transcriptional correlates of long-term sensitization training at different CNS loci in Aplysia californica

Repeated noxious stimulation produces long-term sensitization of defensive withdrawal reflexes in Aplysia californica, a form of long-term memory that requires changes in both transcription and translation. Previous work has identified 10 transcripts which are rapidly up-regulated after long-term sensitization training in the pleural ganglia. Here we use quantitative PCR to begin examining how these transcriptional changes are expressed in different CNS loci related to defensive withdrawal reflexes at 1 and 24 hours after long-term sensitization training. Specifically, we sample from a) the sensory wedge of the pleural ganglia, which exclusively contains the VC nociceptor cell bodies that help mediate input to defensive withdrawal circuits, b) the remaining pleural ganglia, which contain withdrawal interneurons, and c) the pedal ganglia, which contain many motor neurons. Results from the VC cluster show different temporal patterns of regulation: 1) rapid but transient up-regulation of Aplysia homologs of C/EBP, C/EBPγ, and CREB1, 2) delayed but sustained up-regulation of BiP, Tolloid/BMP-1, and sensorin, 3) rapid and sustained up-regulation of Egr, GlyT2, VPS36, and an uncharacterized protein (LOC101862095), and 4) an unexpected lack of regulation of Aplysia homologs of calmodulin (CaM) and reductase-related protein (RRP). Changes in the remaining pleural ganglia mirror those found in the VC cluster at 1 hour but with an attenuated level of regulation. Because these samples had almost no expression of the VC-specific transcript sensorin, our data suggests that sensitization training likely induces transcriptional changes in either defensive withdrawal interneurons or neurons unrelated to defensive withdrawal. In the pedal ganglia, we observed only a rapid but transient increase in Egr expression, indicating that long-term sensitization training is likely to induce transcriptional changes in motor neurons but raising the possibility of different transcriptional endpoints in this cell type.

Characterization of the rapid transcriptional response to long-term sensitization training in Aplysia californica

We used a custom-designed microarray and quantitative PCR to characterize the rapid transcriptional response to long-term sensitization training in the marine mollusk Aplysia californica. Aplysia were exposed to repeated noxious shocks to one side of the body, a procedure known to induce a long-lasting, transcription-dependent increase in reflex responsiveness that is restricted to the side of training. One hour after training, pleural ganglia from the trained and untrained sides of the body were harvested; these ganglia contain the sensory nociceptors which help mediate the expression of long-term sensitization memory. Microarray analysis from 8 biological replicates suggests that long-term sensitization training rapidly regulates at least 81 transcripts. We used qPCR to test a subset of these transcripts and found that 83% were confirmed in the same samples, and 86% of these were again confirmed in an independent sample. Thus, our new microarray design shows strong convergent and predictive validity for analyzing the transcriptional correlates of memory in Aplysia. Fully validated transcripts include some previously identified as regulated in this paradigm (ApC/EBP and ApEgr) but also include novel findings. Specifically, we show that long-term sensitization training rapidly up-regulates the expression of transcripts which may encode Aplysia homologs of a C/EBPγ transcription factor, a glycine transporter (GlyT2), and a vacuolar-protein-sorting-associated protein (VPS36).

Escape and avoidance learning in the earthworm Eisenia hortensis

Interest in instrumental learning in earthworms dates back to 1912 when Yerkes concluded that they can learn a spatial discrimination in a T-maze. Rosenkoetter and Boice determined in the 1970s that the “learning” that Yerkes observed was probably chemotaxis and not learning at all. We examined a different form of instrumental learning: the ability to learn both to escape and to avoid an aversive stimulus. Freely moving “master” worms could turn off an aversive white light by increasing their movement; the behavior of yoked controls had no effect on the light. We demonstrate that in as few as 12 trials the behavior of the master worms comes under the control of this contingency.

Transcriptional changes following long-term sensitization training and in vivo serotonin exposure in Aplysia californica

We used Aplysia californica to compare the transcriptional changes evoked by long-term sensitization training and by a treatment meant to mimic this training, in vivo exposure to serotonin. We focused on 5 candidate plasticity genes which are rapidly up-regulated in the Aplysia genus by in vivo serotonin treatment, but which have not yet been tested for regulation during sensitization: CREB1, matrilin, antistasin, eIF3e, and BAT1 homolog. CREB1 was rapidly up-regulated by both treatments, but the regulation following training was transient, falling back to control levels 24 hours after training. This suggests some caution in interpreting the proposed role of CREB1 in consolidating long-term sensitization memory. Both matrilin and eIF3e were up-regulated by in vivo serotonin but not by long-term sensitization training. This suggests that in vivo serotonin may produce generalized transcriptional effects that are not specific to long-term sensitization learning. Finally, neither treatment produced regulation of antistasin or BAT1 homolog, transcripts regulated by in vivo serotonin in the closely related Aplysia kurodai. This suggests either that these transcripts are not regulated by experience, or that transcriptional mechanisms of memory may vary within the Aplysia genus.

Conditioned food aversion reconsolidation in snails is impaired by translation inhibitors but not by transcription inhibitors

Memory is destabilized during retrieval-induced reconsolidation and can therefore be disrupted or modified. In the present study, we examined the role of translation and transcription processes in long-term food aversion memory reconsolidation in the snail Helix lucorum. The administration of the protein synthesis inhibitor anisomycin followed by a reminding procedure (presentation of the conditioned stimulus) led to the development of amnesia that persist for 2 weeks or longer. Administration of the mRNA synthesis inhibitors actinomycin D, α-amanitin, or DRB (5,6-dichloro-1-β-D-ribofuranosylbenzimidasole) followed by a reminding procedure did not affect memory retrieval. Our present findings indicate that proteins synthesized from preexisting mRNA that is transcribed during learning and stored in a silent state may be involved in the mechanisms of conditioned food aversion reconsolidation.

Species-specific acquisition and consolidation of long-term memory in parasitic wasps

Long-term memory (LTM) formation usually requires repeated, spaced learning events and is achieved by the synthesis of specific proteins. Other memory forms require a single learning experience and are independent of protein synthesis. We investigated in two closely related parasitic wasp species, Cotesia glomerata and Cotesia rubecula, whether natural differences in foraging behaviour are correlated with differences in LTM acquisition and formation. These parasitic wasp species lay their eggs in young caterpillars of pierid butterflies and can learn to associate plant odours with a successful egg laying experience on caterpillars on the odour-producing plant. We used a classical conditioning set-up, while interfering with LTM formation through translation or transcription inhibitors. We show here that C. rubecula formed LTM after three spaced learning trials, whereas C. glomerata required only a single trial for LTM formation. After three spaced learning trials, LTM formation was complete within 4 h in C. glomerata, whereas in C. rubecula, LTM formation took 3 days. Linking neurobiology with ecology, we argue that this species-specific difference in LTM acquisition and formation is adaptive given the extreme differences in both the number of foraging decisions of the two wasp species and in the spatial distributions of their respective hosts in nature.

Inhibition of mRNA synthesis in the hippocampus impairs consolidation and reconsolidation of spatial memory

Using two different mRNA synthesis inhibitors, we show that blockade of hippocampal gene expression during restricted posttraining or postretrieval time windows hinders retention of long-term spatial memory for the Morris water maze task, without affecting short-term memory, nonspatial learning, or the functionality of the hippocampus. Our results indicate that spatial memory consolidation induces the activation of the hippocampal transcriptional machinery and suggest the existence of a gene expression-dependent reconsolidation process that operates in the dorsal hippocampus at the moment of retrieval to stabilize the reactivated mnemonic trace.