Regional expression of neuropeptides in the retina of the terrestrial slug Limax valentianus (Gastropoda, Stylommatophora, Limacidae)

Gastropods use lens-bearing eyes to detect ambient light. The retina contains photoreceptors that directly project to the brain. Here we identified the neurotransmitters that the retinal cells use for projection to the brain in the terrestrial slug Limax. We identified 12 genes encoding neuropeptides as well as a novel vesicular glutamate transporter, a marker of glutamatergic neuron, expressed in the retinal cells. Spatial expression profiles of the neuropeptide genes were determined by in situ hybridization. WWamide/MIP1/Pedal peptide2 were co-expressed in the neurons of the accessory retina. In the main retina, prohormone-4 was expressed in the ventro-lateral region. Clionin was expressed in the ventro-medial region. Pedal peptide was expressed in the anterior region of the main retina and in the accessory retina. Enterin was expressed in many neurons, including the accessory retina, but not in the dorsal region. FxRIamide1 and 2 were co-expressed in the posterior region. Prohormone-4 variant was uniformly expressed in many neurons but scarcely in the accessory retina. MIP2 was widely expressed throughout the dorso-ventral axis in the posterio-lateral region of the main retina. Myo1 was expressed in many neurons of the main retina but predominantly in the dorsal region. These expression patterns were confirmed by immunohistochemistry with specific antibodies against the neuropeptides. Projections of these peptidergic retinal neurons were confirmed by immunostaining of the optic nerve. Our present study revealed regional differentiation of the retina with respect to the neurotransmitters that the retinal cells use. neuropeptides, retina, neurotransmitter, gastropod, Lehmannia This article is protected by copyright. All rights reserved.

GABA-, histamine-, and FMRFamide-immunoreactivity in the visual, vestibular and central nervous systems of Hermissenda crassicornis

Hermissenda crassicornis is a model for studying the molecular and cellular basis for classical conditioning, based on its ability to associate light with vestibular stimulation. We used confocal microscopy to map histamine (HA), FMRF-amide, and γ-aminobutyric acid (GABA) immunoreactivity in the central nervous system (CNS), eyes, optic ganglia and statocysts of the nudibranchs. For HA immunoreactivity, we documented both consistently and variably labeled CNS structures across individuals. We also noted minor differences in GABA immunoreactivity in the CNS compared to previous work on Hermissenda. Contrary to expectations, we found no evidence for GABA inside the visual or vestibular systems. Instead, we found only FMRFamide- and HA immunoreactivity (FMRFamide: 4 optic ganglion cells, 4-5 hair cells; HA: 3 optic ganglion cells, 8 hair cells). Overall, our results can act as basis for comparisons of nervous systems across nudibranchs, and suggest further exploration of intraspecific plasticity versus evolutionary changes in gastropod nervous systems.

Visualization of neuropeptides in paraffin-embedded tissue sections of the central nervous system in the decapod crustacean, Penaeus monodon, by imaging mass spectrometry

The distributions of neuropeptides in paraffin-embedded tissue sections (PETS) of the eyestalk, brain, and thoracic ganglia of the shrimp Penaeus monodon were visualized by imaging mass spectrometry (IMS). Peptide signals were obtained from PETS without affecting morphological features. Twenty-nine neuropeptides comprising members of FMRFamide, SIFamides, crustacean hyperglycaemic hormone, orcokinin-related peptides, tachykinin-related peptides, and allatostatin A were detected and visualized. Among these findings we first identified tachykinin-related peptide as a novel neuropeptide in this shrimp species. We found that these neuropeptides were distributed at specific areas in the three neural organs. In addition, 28 peptide sequences derived from 4 types of constitutive proteins, including actin, histones, arginine kinase, and cyclophilin A were also detected. All peptide sequences were verified by liquid chromatography-tandem mass spectrometry. The use of IMS on acetic acid-treated PETS enabled us to identify peptides and obtain their specific localizations in correlation with the undisturbed histological structure of the tissue samples.