Propranolol disrupts consolidation of emotional memory in Lymnaea

How to reduce fear in a snail: Take an aspirin, call me in the morning

Aspirin (Acetylsalicylic acid, ASA), one of the widely used non-steroid anti-inflammatory drugs can easily end up in sewage effluents and thus it becomes necessary to investigate the effects of aspirin on behaviour of aquatic organisms. Previous studies in mammals have shown ASA to alter fear and anxiety-like behaviours. In the great pond snail Lymnaea stagnalis, ASA has been shown to block a 'sickness state' induced by lipopolysaccharide injection which upregulates immune and stress-related genes thus altering behavioural responses. In Lymnaea, eliciting physiological stress may enhance memory formation or block its retrieval depending on the stimulus type and intensity. Here we examine whether ASA will alter two forms of associative-learning memory in crayfish predator-experienced Lymnaea when ASA exposure accompanies predator-cue-induced stress during the learning procedure. The two trainings procedures are: 1) operant conditioning of aerial respiration; and 2) a higher form of learning, called configural learning, which here is dependent on evoking a fear response. We show here that ASA alone does not alter homeostatic aerial respiration, feeding behaviour or long-term memory (LTM) formation of operantly conditioned aerial respiration. However, ASA blocked the enhancement of LTM formation normally elicited by training snails in predator cue. ASA also blocked configural learning, which makes use of the fear response elicited by the predator cue. Thus, ASA alters how Lymnaea responds cognitively to predator detection.

Disgusted snails, oxytocin, and the avoidance of infection threat

Disgust is considered to be a fundamental affective state associated with triggering the behavioral avoidance of infection and parasite/pathogen threat. In humans, and other vertebrates, disgust affects how individuals interact with, and respond to, parasites, pathogens and potentially infected conspecifics and their sensory cues. Here we show that the land snail, Cepaea nemoralis, displays a similar "disgust-like" state eliciting behavioral avoidance responses to the mucus associated cues of infected and potentially infected snails. Brief exposure to the mucus of snails treated with the Gram-negative bacterial endotoxin, lipopolysaccharide (LPS), elicited dose-related behavioral avoidance, including acute antinociceptive responses, similar to those expressed by mammals. In addition, exposure to the mucus cues of LPS treated snails led to a subsequent avoidance of unfamiliar individuals, paralleling the recognition of and avoidance responses exhibited by vertebrates exposed to potential pathogen risk. Further, the avoidance of, and antinociceptive responses to, the mucus of LPS treated snails were attenuated in a dose-related manner by the oxytocin (OT) receptor antagonist, L-368,899. This supports the involvement of OT and OT receptor homologs in the expression of infection avoidance, and consistent with the roles of OT in the modulation of responses to salient social and infection threats by rodents and other vertebrates. These findings with land snails are indicative of evolutionarily conserved disgust-like states associated with OT/OT receptor homolog modulated behavioral avoidance responses to infection and pathogen threat.

Human health and snails

Snails can provide a considerable variety of bioactive compounds for cosmetic and pharmaceutical industries, useful for the development of new formulations with less toxicity and post effects compared to regular compounds used for the purpose. Compounds from crude extract, mucus, slime consist of glycans, polypeptides, proteins, etc., and can be used for curing diseases like viral lesions, warts, and different dermal problems. Some particular uses of snails involve treating post-traumatic stress. Micro RNA of Lymnaea stagnalis, was known to be responsible for the development of long-term memory and treatment of Alzheimer's and Dementia like diseases. This review explores the application of various bioactive compounds from snails with its potential as new translational medicinal and cosmetic applications. Snail bioactive compounds like ω-MVIIA, μ-SIIIA, μO-MrVIB, Xen2174, δ-EVIA, α-Vc1.1, σ-GVIIA, Conantokin-G, and Contulakin-G, conopeptides can be used for the development of anti-cancer drugs. These compounds target the innate immunity and improve the defense system of humans and provide protection against these life-threatening health concerns.AbbreviationsFDA: Food and Drug Administration; UTI: urinal tract infection; nAChRs: nicotinic acetylcholine receptors; NMDA: N-methyl-D-aspartate; CNS: central nervous system; CAR T: chimeric antigen receptors therapy; Micro RNA: micro ribonucleic acid.

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

A heat stressor (1 h at 30°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, 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. Therefore, 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.

In the great pond snail (Lymnaea stagnalis), two stressors that individually enhance memory in combination block memory formation

Stress plays an important role in memory formation in the great pond snail (Lymnaea stagnalis (Linnaeus, 1758)). Individual stressors have been shown to enhance or to perturb long-term memory (LTM) formation. However, when snails perceive a combination of two stressors, it is unclear the outcome with regards to LTM formation. Here we first show that when L. stagnalis are exposed individually to either a predator stressor (crayfish effluent (CE), which is a kairomone) or a thermal stressor (30 °C), LTM formation is enhanced. In their natural environment, L. stagnalis may experience temperatures approaching 30 °C and they may encounter crayfish at the same time. How such a combination of stressors alters adaptive behaviour is unknown. Here we show that when these two stressors are combined, LTM formation is blocked. Since boiling CE inactivates the kairomone, we used previously boiled CE that we combined with the thermal stressor and found that LTM formation is again enhanced. These data show that (i) it cannot accurately be predicted how a combination of stressors when combined interact to alter LTM formation and (ii) there is a difference between hot CE and room temperature CE.

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

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.

Shell damage leads to enhanced memory formation in Lymnaea

Ecologically relevant stressors alter the ability of the pond snail, Lymnaea stagnalis, to form long-term memory (LTM). Here, we show that an environmentally relevant stressor, shell damage, has a dramatic effect on the enhancement of LTM formation. Damage in the form of a shell clip 24 h before operant conditioning training resulted in long-term memory (LTM) formation following a single 0.5 h training session (TS). Typically, in these snails, two 0.5 h TSs with a 1 h interval between the sessions are required to cause LTM formation. We show here that even with a 72 h interval between shell clip and training, memory enhancement still occurred. The stress associated with shell clip could be mitigated by an ongoing high-Ca^{2 +} pond water environment, an injection of propranolol and a DNA methylation blocker. However, use of an anaesthetic (MgCl₂) during the clip or intermittent exposure to the high-Ca^{2 +} pond water environment did not mitigate the stress associated with the shell clip. Shell clip was also sufficient to cause juvenile snails, which neither learn nor form memory, to gain the capacity to form LTM. Together, the experiments demonstrate that shell clipping is an environmentally relevant stressor that can cause enhancement of LTM formation.