Neurocalcin-like immunoreactivity in embryonic stages of the gastropod molluscs Aplysia californica and Lymnaea stagnalis

The egg-laying behaviour of gastropod molluscs is controlled by peptidergic neuroendocrine cells and has provided an important experimental system for behavioural neurobiology. The genes that code for multiple peptides have been sequenced and the peptides themselves have been identified, thus enabling us to investigate how they act on the nervous system to produce the overt behavioural pattern (reviewed by Geraerts et al. 1988). The two animals that have been studied most extensively are the opisthobranch Aplysia californica and the pulmonate Lymnaea stagnalis. In both cases, the peptidergic neurones controlling egg laying are normally electrically silent (both in vivo and in vitro; Kupfermann, 1967; Pinsker and Dudek, 1977; Kits, 1980; Ter Maat et al. 1986) and produce multiple peptides (Rothman et al. 1983; Geraerts et al. 1985; Sigvardt et al. 1986), which are cleaved from a common protein precursor (Scheller et al. 1983; Vreugdenhil et al. 1988). Before egg laying, the cells produce a long-lasting discharge of action potentials (Pinsker and Dudek, 1977; Ter Maat et al. 1986). This electrical discharge initiates egg-laying behaviour, and during it the peptides (one of which initiates ovulation) are released into the blood. The demonstration, in Aplysia californica, that these peptides could have various effects on the activity of central neurones (reviewed by Mayeri and Rothman, 1985) led to the hypothesis that egg-laying behaviour is a neuroendocrine fixed action pattern controlled and coordinated by the concerted actions of the released peptides (Scheller and Axel, 1984). This hypothesis is also thought to apply to Lymnaea stagnalis (Vreugdenhil et al. 1988) because of the structural similarities between precursors of Aplysia californica and Lymnaea stagnalis egg-laying hormones. In this paper we investigate how the sequence of the various components of the egg-laying behaviour pattern is achieved.

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Comparative Analysis of Neuropeptides in Homologous Interneurons and Prohormone Annotation in Nudipleuran Sea Slugs

Frontiers in Physiology ◽

10.3389/fphys.2021.809529 ◽

2021 ◽

Vol 12 ◽

Author(s):

Colin A. Lee ◽

Elena V. Romanova ◽

Bruce R. Southey ◽

Rhanor Gillette ◽

Jonathan V. Sweedler

Keyword(s):

Mass Spectrometry ◽

Comparative Analysis ◽

Lymnaea Stagnalis ◽

De Novo ◽

Cell Mass ◽

Aplysia Californica ◽

Pleurobranchaea Californica ◽

Sea Slugs ◽

Cell Mass Spectrometry ◽

Peptide Profiles

Despite substantial research on neuronal circuits in nudipleuran gastropods, few peptides have been implicated in nudipleuran behavior. In this study, we expanded the understanding of peptides in this clade, using three species with well-studied nervous systems, Hermissenda crassicornis, Melibe leonina, and Pleurobranchaea californica. For each species, we performed sequence homology analysis of de novo transcriptome predictions to identify homologs to 34 of 36 prohormones previously characterized in the gastropods Aplysia californica and Lymnaea stagnalis. We then used single-cell mass spectrometry to characterize peptide profiles in homologous feeding interneurons: the multifunctional ventral white cell (VWC) in P. californica and the small cardioactive peptide B large buccal (SLB) cells in H. crassicornis and M. leonina. The neurons produced overlapping, but not identical, peptide profiles. The H. crassicornis SLB cells expressed peptides from homologs to the FMRFamide (FMRFa), small cardioactive peptide (SCP), LFRFamide (LFRFa), and feeding circuit activating peptides prohormones. The M. leonina SLB cells expressed peptides from homologs to the FMRFa, SCP, LFRFa, and MIP-related peptides prohormones. The VWC, previously shown to express peptides from the FMRFa and QNFLa (a homolog of A. californica pedal peptide 4) prohormones, was shown to also contain SCP peptides. Thus, each neuron expressed peptides from the FMRFa and SCP families, the H. crassicornis and M. leonina SLB cells expressed peptides from the LFRFa family, and each neuron contained peptides from a prohormone not found in the others. These data suggest each neuron performs complex co-transmission, which potentially facilitates a multifunctional role in feeding. Additionally, the unique feeding characteristics of each species may relate, in part, to differences in the peptide profiles of these neurons. These data add chemical insight to enhance our understanding of the neuronal basis of behavior in nudipleurans and other gastropods.

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Drysdalin, a snake neurotoxin with higher affinity for soluble acetylcholine binding protein from Aplysia californica than from Lymnaea stagnalis

Toxicon ◽

10.1016/j.toxicon.2020.08.030 ◽

2020 ◽

Vol 187 ◽

pp. 86-92

Author(s):

Ritu Chandna ◽

Katarzyna Kaczanowska ◽

Palmer Taylor ◽

R.Manjunatha Kini

Keyword(s):

Lymnaea Stagnalis ◽

Binding Protein ◽

Aplysia Californica ◽

Acetylcholine Binding Protein ◽

Snake Neurotoxin

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The kinematics of swallowing in the buccal mass of Aplysia californica.

Journal of Experimental Biology ◽

10.1242/jeb.200.4.735 ◽

1997 ◽

Vol 200 (4) ◽

pp. 735-752 ◽

Cited By ~ 4

Author(s):

R F Drushel ◽

D M Neustadter ◽

L L Shallenberger ◽

P E Crago ◽

H J Chiel

Keyword(s):

Lymnaea Stagnalis ◽

Aplysia Californica ◽

Spherical Shape ◽

Shape Space ◽

Neutral Position ◽

Buccal Mass ◽

Internal Structures ◽

Direction Of Movement ◽

Dimensional Shape

Changes in the positions, shapes and movements of the feeding apparatus (buccal mass) of the marine mollusc Aplysia californica were studied in intact, transilluminated juveniles. The buccal mass assumes characteristic shapes as its internal structure, the radula/odontophore, moves anteriorly (protracts) or posteriorly (retracts). These shapes are especially distinctive when the radula/odontophore has protracted forwards fully, is close to its resting or neutral position, or has retracted backwards fully. We refer to the shapes that occur at full protraction, transition and full retraction as shape 1 (spherical), shape 2 (ovoid) and shape 3 (gamma-shaped), respectively. We introduce this shape nomenclature in order to avoid confusion with the existing terms protraction and retraction, which we reserve exclusively to describe the direction of movement of the radula/odontophore. The observed shape changes do not agree with those predicted on the basis of in vitro observations of a feeding head preparation, but are similar to shapes observed in vitro in the snail Lymnaea stagnalis. The buccal mass also rotates approximately 10 degrees dorsally during retraction, pivoting on the attachment to the mouth, before the subsequent protraction and return of the buccal mass to the transition shape. This rotation may be due to activation of the extrinsic muscles of the buccal mass. Plots of the buccal mass shape parameters eccentricity versus ellipticity create a two-dimensional shape space, which accurately quantifies the subtle transitions of shape between the different phases of the feeding cycle. Quantitative differences are observed between pure swallows and swallows with tearing behavior, but the qualitative shapes are similar. Hysteresis in the shape space plots of most swallows provides evidence for the hypothesis that protraction and retraction each have distinct 'active' and 'return' phases. The observed kinematic pattern imposes constraints on the internal structures of the buccal mass and may be used to infer the shape and positions of the radula and odontophore.

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Pore properties of Lymnaea stagnalis neuron stretch-activated K+ channels

Journal of Experimental Biology ◽

10.1242/jeb.198.9.1919 ◽

1995 ◽

Vol 198 (9) ◽

pp. 1919-1929

Author(s):

D Small ◽

C Morris

Keyword(s):

Lymnaea Stagnalis ◽

Single Channel ◽

Ion Selectivity ◽

Aplysia Californica ◽

Resting Potential ◽

K Channel ◽

Molluscan Neurons ◽

Membrane Excitability ◽

K Channels ◽

Pore Properties

In many neurons, variations in membrane excitability are determined by a resting K+ conductance whose magnitude is modulated via neurotransmitters. The S-channel in Aplysia californica mechanosensory neurons is such a conductance, but it has also been shown to be a stretch-activated K+ channel. In this, it resembles stretch-activated K+ channels common to all molluscan neurons. Comparable channels are widespread, having been reported in molluscan and insect muscle and various vertebrate cells. The pore properties of the S-channel and similar stretch-activated K+ channels have received only sporadic attention. Here we examine, at the single-channel level, the permeation characteristics of a stretch-activated K+ channel from neurons of the mollusc Lymnaea stagnalis. MichaelisMenten constants (Km) for the conductance, obtained separately for inward (28 mmol l-1) and outward (91 mmol l-1) K+ currents, suggest that the channel presents to the external medium, where [K+] is lower, a higher-affinity site than it presents to the cytoplasmic medium. This may help to ensure that influx is not diffusion-limited at potentials near the resting potential, i.e. near the K+ equilibrium constant. Anomalous mole fraction behavior, observed when the ratio of permeant ion (K+ and Rb+) was varied, indicated that the stretch-activated K+ channel is a multi-ion pore. The ion selectivity sequence determined using reversal potentials under bi-ionic conditions was Cs+>K+>Rb+>NH4+>Na+>Li+, and using relative conductance in symmetrical solutions, the sequence was Tl+=K+>Rb+>NH4+>Na+=Li+=Cs+. Extreme variations in extracellular pH from 4.7 to 11.4 had no effect on stretch-activated K+ channel conductance, whereas normal concentrations of extracellular Mg2+ reduced inward K+ current. Intracellular, but not extracellular, Ba2+ produced a slow, open channel block with an IC50 of 140±80 µmol l-1. These pore properties are compared with those of other stretch-activated K+ channels and of K+ channels in general. In spite of a greater than half order of magnitude difference in the cytoplasmic [K+] in marine (Aplysia californica) and freshwater (Lymnaea stagnalis) molluscs, the conductances of stretch-activated K+ channels from the two groups are very similar.

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