Paired pulse ratio analysis of insulin-induced synaptic plasticity in the snail brain

Murakami, Jun; Okada, Ryuichi; Fujito, Yutaka; Sakakibara, Manabu; Lukowiak, Ken; Ito, Etsuro

doi:10.1242/jeb.083469

Cited by 26 publications

(18 citation statements)

References 11 publications

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“…Our previous studies have indicated that both mammalian insulin and MIPs significantly alter synaptic transmission in the isolated CNS at concentration in the sub-micromolar range (Murakami et al, 2013a(Murakami et al, , 2013b. Here we used a concentration of 100 nM bovine insulin for the in vivo injection.…”

Section: Discussionmentioning

confidence: 99%

“…Our previous experiments demonstrated that both bovine insulin and the human insulin receptor antibody can bind molluscan like insulin peptide (MIP) receptors (Murakami et al, 2013a(Murakami et al, , 2013b. This is because the binding site of Lymnaea MIP receptors is well conserved across phyla.…”

Section: Injection Of Bovine Insulin and Human Insulin Receptor Antibodymentioning

confidence: 99%

“…In that study, we found that some isoforms of molluscan insulin-related peptides were up-regulated. More recently, the effects of insulin were examined in CTA-LTM formation (Hatakeyama, Okuta, Otsuka, Lukowiak, & Ito, 2013;Murakami et al, 2013aMurakami et al, , 2013b. We showed that application of mammalian insulin or molluscan insulin-related peptides to the isolated central nervous system (CNS) induced a long-term enhancement of a synaptic connection, and that this enhancement was blocked by application of an insulin receptor antibody.…”

Section: Introductionmentioning

confidence: 99%

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An increase in insulin is important for the acquisition conditioned taste aversion in Lymnaea

Mita¹,

Yamagishi²,

Fujito³

et al. 2014

Neurobiology of Learning and Memory

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Section: Discussionmentioning

confidence: 99%

Section: Injection Of Bovine Insulin and Human Insulin Receptor Antibodymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

An increase in insulin is important for the acquisition conditioned taste aversion in Lymnaea

Mita¹,

Yamagishi²,

Fujito³

et al. 2014

Neurobiology of Learning and Memory

Self Cite

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“…In addition, when we examined the serotonergic synaptic connection between the CGC and the B1 motor neuron, we found that molluscan insulin-related peptides act to strengthen this connection (Murakami et al 2013a). Our present working hypothesis is that molluscan insulin-related peptides accomplish this by acting on the B1 motor neuron (postsynaptic neuron) but not on the CGC (presynaptic neuron) (Murakami et al 2013b). …”

Section: Function Of Insulin In Postsynaptic Neuronsmentioning

confidence: 99%

“…That is, the CGC and the B1 motor neurons both possess molluscan insulinrelated peptide receptors. To determine if the change in synaptic plasticity of the CGC-B1 synapses brought about by insulin was the result of presynaptic and/or postsynaptic alternations, Murakami et al (2013b) used the paired pulse procedure, in which the amplitude of an initial EPSP was compared with that of a second EPSP elicited shortly after the first EPSP. If the second EPSP is larger than that of the first EPSP, it is called paired pulse facilitation, whereas if the second EPSP is smaller, it is called paired pulse depression.…”

Section: Function Of Insulin In Postsynaptic Neuronsmentioning

confidence: 99%

Function of insulin in snail brain in associative learning

et al. 2015

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Insulin is well known as a hormone regulating glucose homeostasis across phyla. Although there are insulin-independent mechanisms for glucose uptake in the mammalian brain, which had contributed to a perception of the brain as an insulin-insensitive organ for decades, the finding of insulin and its receptors in the brain revolutionized the concept of insulin signaling in the brain. However, insulin's role in brain functions, such as cognition, attention, and memory, remains unknown. Studies using invertebrates with their open blood-vascular system have the promise of promoting a better understanding of the role played by insulin in mediating/modulating cognitive functions. In this review, the relationship between insulin and its impact on long-term memory (LTM) is discussed particularly in snails. The pond snail Lymnaea stagnalis has the ability to undergo conditioned taste aversion (CTA), that is, it associatively learns and forms LTM not to respond with a feeding response to a food that normally elicits a robust feeding response. We show that molluscan insulin-related peptides are up-regulated in snails exhibiting CTA-LTM and play a key role in the causal neural basis of CTA-LTM. We also survey the relevant literature of the roles played by insulin in learning and memory in other phyla.

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FMRF-amide is a glucose-lowering hormone in the snail Helix aspersa

Röszer

Kiss-Tóth

2014

Cell Tissue Res

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Although glucose is metabolically the most important carbohydrate in almost all living organisms, still little is known about the evolution of the hormonal control of cellular glucose uptake. In this study, we identify Phe-Met-Arg-Phe-amide (FMRFa), also known as molluscan cardioexcitatory tetrapeptide, as a glucose-lowering hormone in the snail Helix aspersa. FMRFa belongs to an evolutionarily conserved neuropeptide family and is involved in the neuron-to-muscle signal transmission in the snail digestive system. This study shows that, beyond this function, FMRFa also has glucose-lowering activity. We found neuronal transcription of genes encoding FMRFa and its receptor and moreover the hemolymph FMRFa levels were peaking at metabolically active periods of the snails. In turn, hypometabolism of the dormant periods was associated with abolished FMRFa production. In the absence of FMRFa, the midintestinal gland ("hepatopancreas") cells were deficient in their glucose uptake, contributing to the development of glucose intolerance. Exogenous FMRFa restored the absorption of hemolymph glucose by the midintestinal gland cells and improved glucose tolerance in dormant snails. We show that FMRFa was released to the hemolymph in response to glucose challenge. FMRFa-containing nerve terminals reach the interstitial sinusoids between the chondroid cells in the artery walls. We propose that, in addition to the known sites of possible FMRFa secretion, these perivascular sinusoids serve as neurohemal organs and allow FMRFa release. This study suggests that in evolution, not only the insulin-like peptides have adopted the ability to increase cellular glucose uptake and can act as hypoglycemic hormones.

show abstract

Paired pulse ratio analysis of insulin-induced synaptic plasticity in the snail brain

Cited by 26 publications

References 11 publications

An increase in insulin is important for the acquisition conditioned taste aversion in Lymnaea

An increase in insulin is important for the acquisition conditioned taste aversion in Lymnaea

Function of insulin in snail brain in associative learning

FMRF-amide is a glucose-lowering hormone in the snail Helix aspersa

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