Multiple Subtypes of Serotonin Receptors in the Feeding Circuit of a Pond Snail

Kawai, Rie; Kobayashi, Suguru; Fujito, Yutaka; Ito, Etsuro

doi:10.2108/zsj.28.517

Cited by 30 publications

(18 citation statements)

References 39 publications

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“…However, we do know that food deprivation causes a number of physiological changes in snails. For example, serotonin (5-hydroxytryptamine: 5-HT), a multimodal transmitter, controls both feeding and cardiovascular behaviors in snails (Kemenes et al, 1989;Buckett et al, 1990;Hatakeyama and Ito, 1999;Yamanaka et al, 2000;Kawai et al, 2011). Recently, Yamagishi and colleagues found that food deprivation significantly alters heart rate in Lymnaea .…”

Section: Discussionmentioning

confidence: 99%

Memory block: A consequence of conflict resolution

Ito

Yamagishi

Hatakeyama

et al. 2015

Journal of Experimental Biology

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Food deprivation for 1 day in the pond snail Lymnaea stagnalis before aversive classical conditioning results in optimal conditioned taste aversion (CTA) and long-term memory (LTM) formation, whereas 5-day food deprivation before training does not. We hypothesize that snails do in fact learn and form LTM when trained after prolonged food deprivation, but that severe food deprivation blocks their ability to express memory. We trained 5-day food-deprived snails under various conditions, and found that memory was indeed formed but is overpowered by severe food deprivation. Moreover, CTA-LTM was context dependent and was observed only when the snails were in a context similar to that in which the training occurred.

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Section: Discussionmentioning

confidence: 99%

Memory block: A consequence of conflict resolution

Ito

Yamagishi

Hatakeyama

et al. 2015

Journal of Experimental Biology

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“…The resistance of these microelectrodes ranged from 50 to 70 MΩ. We intracellularly recorded a compound EPSP in the B1 motor neuron that was evoked by bursting action potentials in the CGC [28]. The constant depolarizing current was injected into the CGC for 1 s to elicit the bursting action potentials using the amplifier's built-in function for current injection.…”

Section: Methodsmentioning

confidence: 99%

Memory Trace in Feeding Neural Circuitry Underlying Conditioned Taste Aversion in Lymnaea

et al. 2012

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BackgroundThe pond snail Lymnaea stagnalis can maintain a conditioned taste aversion (CTA) as a long-term memory. Previous studies have shown that the inhibitory postsynaptic potential (IPSP) evoked in the neuron 1 medial (N1M) cell by activation of the cerebral giant cell (CGC) in taste aversion-trained snails was larger and lasted longer than that in control snails. The N1M cell is one of the interneurons in the feeding central pattern generator (CPG), and the CGC is a key regulatory neuron for the feeding CPG.Methodology/Principle FindingsPrevious studies have suggested that the neural circuit between the CGC and the N1M cell consists of two synaptic connections: (1) the excitatory connection from the CGC to the neuron 3 tonic (N3t) cell and (2) the inhibitory connection from the N3t cell to the N1M cell. However, because the N3t cell is too small to access consistently by electrophysiological methods, in the present study the synaptic inputs from the CGC to the N3t cell and those from the N3t cell to the N1M cell were monitored as the monosynaptic excitatory postsynaptic potential (EPSP) recorded in the large B1 and B3 motor neurons, respectively. The evoked monosynaptic EPSPs of the B1 motor neurons in the brains isolated from the taste aversion-trained snails were identical to those in the control snails, whereas the spontaneous monosynaptic EPSPs of the B3 motor neurons were significantly enlarged.Conclusion/SignificanceThese results suggest that, after taste aversion training, the monosynaptic inputs from the N3t cell to the following neurons including the N1M cell are specifically facilitated. That is, one of the memory traces for taste aversion remains as an increase in neurotransmitter released from the N3t cell. We thus conclude that the N3t cell suppresses the N1M cell in the feeding CPG, in response to the conditioned stimulus in Lymnaea CTA.

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“…The serotonergic EPSP in the B1 motor neuron is mediated via at least two types of serotonin receptors: metabotropic 5-HT 2 -like receptors and ionotropic 5-HT 3 -like receptors (Kawai et al, 2011). The fast component of compound EPSP is mediated by 5-HT 3 -like receptors, and the slow component is generated via 5-HT 2 -like receptors.…”

Section: Results and Discussion Contribution From A Presynaptic Neuromentioning

confidence: 99%

“…Insulin may evoke a rapid recruitment of functional GABA A receptors to the postsynaptic membrane, suggesting a fundamental mechanism for the generation of synaptic plasticity. At the CGC-B1 synapses in L. stagnalis, serotonin appears to be the likely transmitter substance (Kawai et al, 2011), so it is possible that MIPs could result in an increase in serotonin receptors (possibly ionotropic 5-HT 3 -like receptors) on the B1 motor neurons. This possibility is currently being examined.…”

Section: Possible Function Of Insulin In a Long-term Synaptic Enhancementioning

confidence: 99%

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

Murakami

Okada

Fujito

et al. 2013

Journal of Experimental Biology

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SUMMARYInsulinʼs action in the brain can directly alter cognitive functioning. We have recently shown that molluscan insulin-related peptides are upregulated following a conditioned taste aversion (CTA) training procedure. In addition, when mammalian insulin is superfused over the isolated Lymnaea stagnalis central nervous system, it elicits long-term synaptic enhancement at the monosynaptic connection between the cerebral giant cell and the buccal 1 (B1) motor neuron. This synaptic enhancement is thought to be a neural correlate of CTA. Here, we examined whether the observed changes in synaptic plasticity were the result of presynaptic and/or postsynaptic alterations using the paired pulse procedure. The paired pulse ratio was unaltered following insulin application, suggesting that insulinʼs effects on synaptic plasticity are mediated postsynaptically in the B1 motor neuron. Thus, it was suggested that postsynaptic changes need to be considered when insulinʼs actions on synaptic plasticity are examined.

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Multiple Subtypes of Serotonin Receptors in the Feeding Circuit of a Pond Snail

Cited by 30 publications

References 39 publications

Memory block: A consequence of conflict resolution

Memory block: A consequence of conflict resolution

Memory Trace in Feeding Neural Circuitry Underlying Conditioned Taste Aversion in Lymnaea

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

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