Shell damage leads to enhanced memory formation in Lymnaea

Shymansky

Journal of Experimental Biology

et al. 2020

Self Cite

Stress alters both memory formation and its retrieval. Here, we show that a combination of stressors before an associative learning event alters memory retrieval of a non-declarative memory in an invertebrate model system. Previously, two combinations of stressors were purported to prevent long-term memory (LTM) formation in 'smart' Lymnaea and this inability to form LTM was considered to be a cost of being smart. Here, we show that is not the case. The specific combinations of stressors used here cause emotional memory formation. Previously, it was shown that propranolol, a synthetic beta-blocker, altered emotional memory in Lymnaea. We show here that when propranolol but not saline is injected into smart snails before they perceive the combination of stressors, these snails form LTM. We then show that the injection of propranolol but not saline before a memory activation session allowed the memory to be recalled. That is, LTM formed but was not retrievable unless propranolol was injected pre-retrieval. Thus, the smart snails formed LTM in the face of the stressors but could not retrieve it.

Section: Discussionsupporting

confidence: 73%

Stress before training alters memory retrieval of a non-declarative memory in Lymnaea

Shymansky

Journal of Experimental Biology

et al. 2020

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“…Massarsky et al (2011) posited that the OA and NA systems are homologous. We had hypothesized that propranolol brought about its blocking effect on LTM enhancement by its effect on OA receptors (Shymansky et al, 2018;Swinton et al, 2019;. This hypothesis was supported by findings showing that OA was involved in mediating stress in molluscs (Fabbri and Capuzzo, 2010).…”

Section: Introductionmentioning

confidence: 90%

A thermal stressor, propranolol and long-term memory formation in freshly collected Lymnaea

Journal of Experimental Biology

Phillips

et al. 2021

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A heat stressor (1h at 30o C) in Lymnaea stagnalis before operant conditioning training of aerial respiration is sufficient to enhance long-term memory (LTM) formation in average cognitive-ability, laboratory-reared, inbred snails. However, in freshly collected outbred snails the same heat stressor blocks LTM formation in smart cognitive phenotype but not in average cognitive phenotype strains. Here we hypothesize that: 1) preventing the stress associated with the heat stressor before training allows LTM to form in the smart phenotype strains ; and 2) alleviating the stress before a memory recall session allows a formed LTM to be recalled in the smart phenotype strains. We found that an injection of propranolol, which mitigates the stressor, before snails experience the heat stressor enabled two strains of the smart phenotype snails to form LTM formation, consistent with our first hypothesis. However, the injection of propranolol before a memory test session, did not alleviate a memory recall block in the smart phenotype snails. Thus, our second hypothesis was not supported. Thus, smart cognitive phenotype snails encountering a heat stressor have an inability to form LTM, but this inability can be overcome by the pre-injection of propranolol.

“…Then, we examined whether their feeding response to a carrot slurry (C), a new appetitive stimulus, which elicits a robust rasping behavior, before (C-pre) and 3 h after (C-post 3 h) HS exposure was significantly reduced, resulting in a Garcia effect. Thus, AL, D1, and D5 snails were exposed to C [56, 57], 1 h before and 3 h after the exposure to the HS as previously described.…”

Section: Methodsmentioning

confidence: 99%

Behavioral and Transcriptional Effects of Short or Prolonged Fasting on the Memory Performances of Lymnaea stagnalis

et al. 2022

Introduction: The Garcia effect, a solid learning paradigm, was used to investigate the molecular and behavioral effects induced by different lengths of fasting on the cognitive functions in the pond snail Lymnaea stagnalis, a valid model system Methods: Three experimental groups were used: Moderately hungry snails, food-deprived for 1 day (D1 snails), severely hungry snails (D5 snails), fasting for 5 days, and satiated snails with ad libitum access to food (AL snails). In the Garcia effect, a single pairing of an appetitive stimulus with a heat stressor results in a learned taste-specific negative hedonic shift. D5 snails were injected with bovine insulin and D1 snails with the insulin receptor antibody (Ab). As a control group, AL snails were injected with saline. Gene expression analyses were performed by Real-time PCR in snails’ central nervous system (CNS). Results: AL snails are ‘average learners’, D1 snails are the best performers, whereas the D5 ones do not show the Garcia effect. Severely fasting snails injected with insulin 3h before the training procedure, show the Garcia effect, whereas injecting 1-day fasting snails with insulin receptor Ab blocks their ability to express memory. The differences in memory performances are associated with changes in the expression levels of selected targets involved in neuronal plasticity, energy homeostasis, and stress response. Discussion: Our results suggest that short-term fasting creates an optimal internal state in L. stagnalis’ CNS, allowing a spike in insulin release and an upregulation of genes involved in neuroplasticity. Long-term fasting, instead, upregulates genes involved in energy homeostasis and animal survival.