Background: The freshwater snail Lymnaea stagnalis (L. stagnalis) has served as a successful model for studies in the field of Neuroscience. However, a serious drawback in the molecular analysis of the nervous system of L. stagnalis has been the lack of large-scale genomic or neuronal transcriptome information, thereby limiting the use of this unique model.

Peptide profiles of single neurons in Lymnaea stagnalis were directly characterized by matrix-assisted laser desorptiowionization mass spectrometry. The mass analysis was performed after minor pretreatment and without any separation steps. Good-quality spectra were obtained of several cell types and also other tissues. The results were compared with the results of conventional peptide chemical methods. In addition to many known peptides, several new peptides were identified. The method provides new opportunities for studying peptide compositions at the single-cell level, which is shown to have many advantages.

No abstract

Age-dependent impairment in learning and memory functions occurs in many animal species, including humans. Although cell death contributes to age-related cognitive impairment in pathological forms of aging, learning and memory deficiencies develop with age even without substantial cell death. The molecular and cellular basis of this biological aging process is not well understood but seems to involve a decline in the aging brain's capacity for experience-dependent plasticity. To aid in resolving this issue, we used a simple snail appetitive classical conditioning paradigm in which the underlying molecular, cellular, and neural network functions can be directly linked to age-associated learning and memory performance (i.e., the Lymnaea stagnalis feeding system). Our results indicate that age does not affect the acquisition of appetitive memory but that retention and/or consolidation of long-term memory become progressively impaired with advancing age. The latter phenomenon correlates with declining electrophysiological excitability in key neurons controlling the feeding behavior. Together, these results present the Lymnaea feeding system as a powerful paradigm for investigations of cellular and molecular foundations of biological aging in the brain.

The mammalian epidermal growth factor (EGF) is expressed in the developing and adult CNS, and it has been implicated in the control of cell proliferation, differentiation, and neurotrophic events. Despite extensive evolutionary conservation of the EGF motif in a range of different types of proteins, secreted EGF homologs with neurotrophic actions have not been reported in invertebrates. In this study, we present a novel member of the family of EGF-like growth factors, an EGF homolog from the mollusc Lymnaea stagnalis (L-EGF), and we demonstrate that this protein has neurotrophic activity. Purified L-EGF is a 43-residue peptide and retains the typical structural characteristics of the EGF motif. The L-EGF cDNA reveals a unique precursor organization. In contrast to the multidomain mammalian EGFs, it consists of only two domains, a signal peptide and a single EGF motif. Conspicuously, the L-EGF precursor lacks a transmembrane domain, setting it apart from all other members of the EGF-family. L-EGF mRNA is expressed throughout embryonic development, in the juvenile CNS, but not in the normal adult CNS. However, expression in the adult CNS is upregulated after injury, suggesting a role of L-EGF in repair functions. This notion is supported by the observation that L-EGF evokes neurite outgrowth in specific adult Lymnaea neurons in vitro, which could be inhibited by an EGF receptor tyrosine kinase inhibitor. In conclusion, our findings further substantiate the notion that the EGF family has an early phylogenetic origin, and our data support a neurotrophic role for L-EGF during development and injury repair.