Nav1.6 but not KCa3.1 channels contribute to heterogeneity in coding abilities and dynamics of action potentials in the L5 neocortical pyramidal neurons.

Electrophysiological and genetic studies reveal two major subclasses of layer 5 (L5) neocortical pyramidal neurons that differ in electrical parameters and afterhyperpolarization. KCa3.1 channels are identified as contributors to slow afterhyperpolarization (sAHP), and they are expressed by one subclass of L5 neurons.

Ca-activated KCa3.1 potassium channels contribute to the slow afterhyperpolarization in L5 neocortical pyramidal neurons.

Layer 5 neocortical pyramidal neurons are known to display slow Ca-dependent afterhyperpolarization (sAHP) after bursts of spikes, which is similar to the sAHP in CA1 hippocampal cells. However, the mechanisms of sAHP in the neocortex remain poorly understood. Here, we identified the Ca-gated potassium KCa3.

Immediate-Early Genes Detection in the CNS of Terrestrial Snail.

In the present work, using in situ hybridization, we studied the expression patterns of three molluscan homologs of vertebrate immediate-early genes C/EBP, c-Fos, and c-Jun in the central nervous system (CNS) of terrestrial gastropod snail Helix. The molluscan C/EBP gene was described in literature, while c-Fos and c-Jun were studied in terrestrial snails for the first time. Localization of the expression was traced in normal conditions, and in preparations physiologically activated using stimulation of suboesophageal ganglia nerves.

Identification of Immediate Early Genes in the Nervous System of Snail .

Immediate early genes (IEGs) are useful markers of neuronal activation and essential components of neuronal response. While studies of gastropods have provided many insights into the basic learning and memory mechanisms, the genome-wide assessment of IEGs has been mainly restricted to vertebrates. In this study, we identified IEGs in the terrestrial snail In the absence of the genome, we conducted transcriptome assembly using reads with short and intermediate lengths cumulatively covering more than 98 billion nucleotides.

A BK channel-mediated feedback pathway links single-synapse activity with action potential sharpening in repetitive firing.

Action potential shape is a major determinant of synaptic transmission, and mechanisms of spike tuning are therefore of key functional significance. We demonstrate that synaptic activity itself modulates future spikes in the same neuron via a rapid feedback pathway. Using Ca imaging and targeted uncaging approaches in layer 5 neocortical pyramidal neurons, we show that the single spike-evoked Ca rise occurring in one proximal bouton or first node of Ranvier drives a significant sharpening of subsequent action potentials recorded at the soma.

Long-living RNA in the CNS of terrestrial snail.

Click-iT method can be used to trace the neurons where the newly synthesized RNA transcripts occur. Our experiments performed with the CNS of terrestrial mollusk Helix demonstrate that 5-ethynyluridine (EU) is selectively incorporated in RNA but not in DNA. The time of EU accumulation necessary for its detection was about several hours.

Adaptive Changes in the Vestibular System of Land Snail to a 30-Day Spaceflight and Readaptation on Return to Earth.

The vestibular system receives a permanent influence from gravity and reflexively controls equilibrium. If we assume gravity has remained constant during the species' evolution, will its sensory system adapt to abrupt loss of that force? We address this question in the land snail exposed to 30 days of near weightlessness aboard the Bion-M1 satellite, and studied geotactic behavior of postflight snails, differential gene expressions in statocyst transcriptome, and electrophysiological responses of mechanoreceptors to applied tilts. Each approach revealed plastic changes in the snail's vestibular system assumed in response to spaceflight.

Encoding of High Frequencies Improves with Maturation of Action Potential Generation in Cultured Neocortical Neurons.

The ability of neocortical neurons to detect and encode rapid changes at their inputs is crucial for basic neuronal computations, such as coincidence detection, precise synchronization of activity and spike-timing dependent plasticity. Indeed, populations of cortical neurons can respond to subtle changes of the input very fast, on a millisecond time scale. Theoretical studies and model simulations linked the encoding abilities of neuronal populations to the fast onset dynamics of action potentials (APs).

Impairment of the serotonergic neurons underlying reinforcement elicits extinction of the repeatedly reactivated context memory.

We analyzed changes in the activity of individually identifiable neurons involved in the networks underlying feeding and withdrawal behaviors in snails before, during, and after aversive learning in vitro. Responses to food in the "reinforcing" serotonergic neurons involved in withdrawal changed significantly after training, implying that these serotonergic cells participate in the reactivation of memory and are involved in the reconsolidation process. In behavioral experiments it was shown that impairment of the functioning of the serotonergic system with the selective neurotoxin 5,7-DiHT did not change the memory, when tested once, but resulted in a complete extinction of the contextual memory after repeated reactivation of memory.

RNA synthesis and turnover in the molluscan nervous system studied by Click-iT method.

RNA synthesis can be detected by means of the in vivo incorporation of 5-ethynyluridine (EU) in newly-synthesized RNA with the relatively simple Click-iT method. We used this method to study the RNA synthesis in the CNS tissue of adult and juvenile terrestrial snails Helix lucorum L. Temporally, first labeled neurons were detected in the adult CNS after 4-h of isolated CNS incubation in EU solution, while 12-h of incubation led to extensive labeling of most CNS neurons.

Homolog of protein kinase Mζ maintains context aversive memory and underlying long-term facilitation in terrestrial snail Helix.

It has been shown that a variety of long-term memories in different regions of the brain and in different species are quickly erased by local inhibition of protein kinase Mζ (PKMζ), a persistently active protein kinase. Using antibodies to mammalian PKMζ, we describe in the present study the localization of immunoreactive molecules in the nervous system of the terrestrial snail Helix lucorum. Presence of a homolog of PKMζ was confirmed with transcriptomics.

Expression of the type 1 metalloproteinase in the rat hippocampus after the intracerebroventricular injection of β-amyloid peptide (25-35).

The expression of matrix metalloproteinase of the first type was studied in frontal sections of the adult rat brain one month after a single intracerebroventricular injection of beta-amyloid peptide (25-35), which is known to be a well-known model of the development of Alzheimer's disease. Brain sections were stained immunocytochemically to detect MMP-1 expression, and histologically to reveal the state of hippocampal neurons. Administration of beta-amyloid peptide induced a significant degeneration of cells in the dorsal hippocampus.

Type 1 metalloproteinase is selectively expressed in adult rat brain and can be rapidly up-regulated by kainate.

The expression of metalloproteinase MMP-1 was traced in frontal sections of the rat brain in normal conditions and 4 h after an intraperitoneal injection of kainate. In the olfactory lobe, immunoreactivity was normally detected in the lateral olfactory tract. Kainate treatment led to the appearance of additional immunoreactivity in the neuropilar tracts.

Biolistic delivery of voltage-sensitive dyes for fast recording of membrane potential changes in individual neurons in rat brain slices.

Optical recording of membrane potential changes with fast voltage-sensitive dyes (VSDs) in neurons is one of the very few available methods for studying the generation and propagation of electrical signals to the distant compartments of excitable cells. The more lipophilic is the VSD, the better signal-to-noise ratio of the optical signal can be achieved. At present there are no effective ways to deliver water-insoluble dyes into the membranes of live cells.

Functional changes in the snail statocyst system elicited by microgravity.

Background: The mollusk statocyst is a mechanosensing organ detecting the animal's orientation with respect to gravity. This system has clear similarities to its vertebrate counterparts: a weight-lending mass, an epithelial layer containing small supporting cells and the large sensory hair cells, and an output eliciting compensatory body reflexes to perturbations.

Methodology/principal Findings: In terrestrial gastropod snail we studied the impact of 16- (Foton M-2) and 12-day (Foton M-3) exposure to microgravity in unmanned orbital missions on: (i) the whole animal behavior (Helix lucorum L.

Family of CNP neuropeptides: common morphology in various invertebrates.

Neuropeptides expressed in the command neurons for withdrawal behavior were originally detected in the the central nervous system (CNS) of the terrestrial snail Helix (command neurons peptides, CNP). The family of CNP-like neuropeptides bears a C-terminal signature sequence Tyr-Pro-Arg-X. Using antisera against two of them, we have studied the CNS of various invertebrates belonging to the phyla of mollusks, annelids and insects.

Two morphological sub-systems within the olfactory organs of a terrestrial snail.

In the present work, we have re-visited the problem of the olfactory neural system organization in the terrestrial snail. By staining the tentacle's nerves and their intrinsic tracts in different points of the cerebral ganglia-tentacles system we have found that the relatively small part of the primary sensory neurons from the sensory pad (7-8%) send their axons directly to the cerebral ganglia. The axons terminated in the metacerebral neuropil which suggests these receptors being not chemosensory but rather mechanosensory neurons.

Cannabinoid regulation in identified synapse of terrestrial snail.

In the terrestrial snail a direct monosynaptic glutamatergic connection between the primary sensory neuron and a premotor interneuron involved in withdrawal behaviour can be functionally identified using electrophysiological techniques. We investigated the involvement of cannabinoids in regulation of this synaptic contact. The results demonstrate that the specific binding sites for agonists to mammalian type 1 cannabinoid receptors (CB1Rs) exist in the snail's nervous system.

Primary sensory neurons containing command neuron peptide constitute a morphologically distinct class of sensory neurons in the terrestrial snail.

In the central nervous system of the terrestrial snail Helix, the gene HCS2, which encodes several neuropeptides of the CNP (command neuron peptide) family, is mostly expressed in cells related to withdrawal behavior. In the present work, we demonstrate that a small percentage (0.1%) of the sensory cells, located in the sensory pad and in the surrounding epithelial region ("collar") of the anterior and posterior tentacles, is immunoreactive to antisera raised against the neuropeptides CNP2 and CNP4, encoded by the HCS2 gene.

Neuropeptides of Drosophila related to molluscan neuropeptides: dependence of the immunoreactivity pattern on the ontogenetic stage and functional state.

The CNP neuropeptides (Command Neuron Peptides) were first found in the command neurons for withdrawal behavior in the terrestrial snail. Given the fact that certain peptides can be found in various invertebrates, we examined Drosophila brains to determine if CNP-like peptides were present. Two types of antisera were used: one against CNP2, which was expected to recognize peptide products of the genes "hugin", "capa", CG6371, and a second antiserum against CNP4, which was expected to recognize neuropeptides encoded by the gene "capa" only.

Intracellular localization of the HCS2 gene products in identified snail neurons in vivo and in vitro.

1. The HCS2 (Helix command specific 2) gene expressed in giant command neurons for withdrawal behavior of the terrestrial snail Helix lucorum encodes a unique hybrid precursor protein that contains a Ca-binding (EF-hand motif) protein and four small peptides (CNP1-CNP4) with similar Tyr-Pro-Arg-X aminoacid sequence at the C terminus. Previous studies suggest that under conditions of increased intracellular Ca(2+) concentration the HCS2 peptide precursor may be cleaved, and small physiologically active peptides transported to the release sites.

Immunoreactivity to molluskan neuropeptides in the central and stomatogastric nervous systems of the earthworm, Lumbricus terrestris L.

Polyclonal antisera against two related command neuropeptides (CNP2 and CNP4) described in neurons of the terrestrial snail Helix were used in a study of the nervous system of the earthworm Lumbricus. The CNP-like peptides belong to the same neuropeptide subfamily and bear a C-terminal signature sequence Tyr-Pro-Arg-X. The distribution patterns of immunoreactive (IR) neurons were studied in the central nervous system (CNS), skin, and stomatogastric nervous system of the earthworm.

Caspase-like activity is essential for long-term synaptic plasticity in the terrestrial snail Helix.

Although caspase activity in the nervous system of mollusks has not been described before, we suggested that these cysteine proteases might be involved in the phenomena of neuroplasticity in mollusks. We directly measured caspase-3 (DEVDase) activity in the Helix lucorum central nervous system (CNS) using a fluorometrical approach and showed that the caspase-3-like immunoreactivity is present in the central neurons of Helix. Western blots revealed the presence of caspase-3-immunoreactive proteins with a molecular mass of 29 kDa.

Snail peptide expression pattern in the nervous system of the medicinal leech.

Distribution of neurons immunopositive to antibodies against the "command neuron peptides" (CNPs) encoded by the snail Helix Command-Specific 2 (HCS2) gene was investigated in the nervous system of medicinal leech Hirudo. Immunopositive neurons were found in the leech segmental ganglia, brain and tail ganglionic masses, and peripheral ganglia. The CNPs immunopositive fibers were observed in neuropils of all ganglia and in some nerves.

Morphological basis for coordination of growth and reproduction processes in the CNS of two terrestrial snails.

The morphology of cells immunoreactive to an antibody against molluscan insulin-related peptide (MIP-IR) was studied in two species of terrestrial snail: Helix lucorum L. and Eobania vermiculata L. Immunocytochemical staining with this antibody to MIP revealed 100-130 cells in the postcerebrum, located in two clusters with common pathways in the dorsal body nerve and the cerebral artery nerve.