RÉSUMÉ
The study explored the potential of an animal opsin nonselectively expressed in various neuronal elements of the degenerative retina to restore the impaired visual function. A knockout murine model of inherited retinal dystrophy was used. Mice were injected intravitreally with either a virus carrying the gene of short-wavelength cone opsin associated with a reporter fluorescent protein or a control virus carrying the sequence of a modified fluorescent protein with enhanced membrane tropism. Viral transduction induced pronounced opsin expression in ganglion, bipolar, and horizontal retinal neurons. Behavioral testing included the visually guided task in the trapezoid Morris water maze and showed a partial recovery of the learning ability in the mice whose retinas had been transduced with cone opsin.
Sujet(s)
Opsines des cônes , Dégénérescence de la rétine , Souris , Animaux , Opsines des cônes/génétique , Opsines des cônes/métabolisme , Dégénérescence de la rétine/génétique , Dégénérescence de la rétine/métabolisme , Cellules photoréceptrices en cône de la rétine/métabolisme , Rétine , Opsines/métabolisme , Souris knockoutRÉSUMÉ
Anion-selective opsins slow ChloC and ACR2 were expressed in rat brain cortical neurons by electroporation in utero. It is shown that the light-activated channel ACR2 has pronounced advantages in terms of both the inactivation kinetics and the neuron inhibition intensity, which is associated with a more negative value of the light-activated current reversal potential compared to the slow ChloC channel. The identified properties of opsin ACR2 indicate that it can be used for strictly controlled suppression of neuronal activity in optogenetic experiments, including the expression in the retinal ganglionic cells for reconstituting the OFF-component of their receptive field, which is essential for optogenetic prosthetics of degenerative retina.
Sujet(s)
Optogénétique , Rhodopsine/métabolisme , Canal anionique-2 voltage-dépendant/métabolisme , Animaux , Cortex cérébral/physiologie , Cortex cérébral/effets des radiations , Électroporation , Lumière , Potentiels de membrane/physiologie , Potentiels de membrane/effets des radiations , Neurones/physiologie , Neurones/effets des radiations , Optogénétique/méthodes , Techniques de patch-clamp , Rats , Rhodopsine/génétique , Techniques de culture de tissus , Canal anionique-2 voltage-dépendant/génétiqueRÉSUMÉ
Recent studies have revealed.that in contrast to invertebrate systems, the initiation of action potentials in vertebrate neurons significantly differ from the relatively slow exponential dynamics predicted by Hodgkin-Huxley equations, but rather is characterized by a sharp onset with a kink. These data provided new insights into the link between action potential initiation and abilities of neurons and neuronal networks to encode. high frequency signals. Here, we review recent models describing sharp onset dynamics of action potential initiation, including an alternative model of cooperative activation of sodium channels, as well as the influence of the dynamics of action potential initiation on computational abili- ties of neuronal networks. The importance this topic is due to the fact that, despite the rapid development of neuronal modeling during last decades, the well established models are unable to capture experimentally observed details of the onset dynamics of action potentials in mammalian neurons and the abilities of neurons to reliably encode code high frequency signals Recent advances of experimental and theoretical analysis of generation of action potentials and neuronal encoding, presented in this review, are ofgreat importance for better understanding of neuronal processing and development of a more precise and realistic neuronal model.
Sujet(s)
Potentiels d'action/physiologie , Invertébrés/physiologie , Modèles neurologiques , Réseau nerveux/physiologie , Neurones/physiologie , Vertébrés/physiologie , Animaux , Cinétique , Réseau nerveux/anatomie et histologie , Neurones/cytologie , Canaux sodiques/physiologie , Facteurs tempsRÉSUMÉ
Anionic channelrhodopsin slow ChloC was expressed in the culture of nerve cells and in vivo in mouse brain. We demonstrated ability of slow ChloC to suppress effectively the activity of the neuron in response to the illumination with the visible light. It has been shown for a first time that slow ChloC works equally efficiently in both neuronal culture and in the whole brain being expressed in vivo. Thus, slow ChloC could be considered as an effective optogenetic tool capable in response to light stimulation to inhibit the generation of action potentials in the neuron.
Sujet(s)
Potentiels d'action , Encéphale/métabolisme , Neurones/métabolisme , Rhodopsine/métabolisme , Animaux , Encéphale/cytologie , Encéphale/physiologie , Cellules cultivées , Lumière , Souris , Neurones/physiologie , Optogénétique/méthodes , Rhodopsine/génétique , Rhodopsine/effets des radiationsRÉSUMÉ
The aims of the present work were to study the role of neuropeptide CNP4, encoded by the HCS2 gene (which is expressed mainly in parietal command interneurons), in controlling the activity of the respiratory system, and also to study the effects of this neuropeptide on isolated defensive behavior neurons in prolonged culture. The influence of the command interneuron on the pneumostoma included a direct effect consisting of closure and a delayed effect consisting of intensification of respiratory movements. Application of neuropeptide CNP4 produced a pattern similar to the delayed effects seen on stimulation of the command interneuron, i.e., significant increases in the frequency and intensity of pneumostoma movements and strengthening of the rhythmic activity of the pneumostoma motoneuron. Studies of the effects of neuropeptide CNP4 on isolated neurons after prolonged culture showed that neuron process growth correlated with the presence of the neuropeptide in the medium. Identification of the location of the HCS2 precursor protein and neuropeptide CNP4 in isolated command interneurons after prolonged culture showed that that only those parts of the cell showing active process growth were immunopositive. Thus, neuropeptide CNP4 appears to be a secreted neuropeptide controlling respiratory system activity, which may also be involved in rearrangements of the network controlling defensive behavior in Helix snails.
Sujet(s)
Protéines de liaison au calcium/physiologie , Ganglions des invertébrés/physiologie , /physiologie , Interneurones/physiologie , Motoneurones/physiologie , Neuropeptides/physiologie , Animaux , Protéines de liaison au calcium/métabolisme , Cellules cultivées , Ganglions des invertébrés/cytologie , Immunohistochimie , Interneurones/métabolisme , Neuropeptides/métabolisme , RespirationRÉSUMÉ
The possible existence of intrasynaptic ephaptic feedback in the invertebrate CNS was studied. Intracellular recordings were made of excitatory postsynaptic potentials and currents arising on activation of the recently described monosynaptic connection between identified neurons in the snail CNS. In the presence of ephaptic feedback, tetanization of the postsynaptic neuron with hyperpolarizing impulses should activate presynaptic calcium channels, thus increasing the amplitude of excitatory postsynaptic potential, while sufficiently strong postsynaptic hyperpolarization applied during generation of the excitatory postsynaptic current should induce "supralinear" increases in its amplitude, as has been observed previously in rat hippocampal neurons. The first series of experiments involved delivery of 10 trains of hyperpolarizing postsynaptic impulses (40-50 mV, duration 0.5 sec, frequency 1 Hz, train duration 45 sec); significant changes in the amplitude of excitatory postsynaptic were not seen. In the second series of experiments, changes in the amplitude of the excitatory postsynaptic current were studied during hyperpolarization of the postsynaptic neuron. At a potential of -100 mV, the amplitude of the excitatory postsynaptic current increased significantly more than predicted by its "classical" linear relationship with membrane potential. This "supralinear" increase in the amplitude of the excitatory postsynaptic potential can be explained by the operation of ephaptic feedback and is the first evidence for this phenomenon in CNS synapses of invertebrates.
Sujet(s)
Potentiels post-synaptiques excitateurs/physiologie , Rétroaction/physiologie , Ganglions des invertébrés/physiologie , Escargots/physiologie , Synapses/physiologie , Animaux , Canaux calciques/physiologie , Stimulation électrique , Potentiels de membrane/physiologieRÉSUMÉ
Rhythmic activity in two independent structures of the digestive apparatus of Clione limacina--the radula and the hooks--is coordinated by neural networks in the buccal ganglion during feeding behavior. Optical recording of neuron activity in the buccal ganglion, which allows simultaneous recording of large numbers of neurons, showed that the activity of all neurons producing volley discharges can be assigned to only two phases of a single rhythm. Instead of the four theoretically possible phases of rhythmic neural activity, all experiments yielded recordings of biphasic activity, even in conditions of electrical stimululation of the cerebrobuccal connectives, which triggers rhythmic movements of this apparatus in preparations. These data demonstrate the phase-dependent coordination of two independent rhythmic food-procuring movements in Clione.