Találati lista | Tudóstér

001-es BibID:	BIBFORM040326
035-os BibID:	PMID:14523064
Első szerző:	Melnick, Igor V.
Cím:	Ionic basis of tonic firing in spinal substantia gelatinosa neurons of rat / Igor V. Melnick, Sónia F. A. Santos, Karolina Szokol, Péter Szűcs, Boris V. Safronov
Dátum:	2004
ISSN:	0022-3077
Megjegyzések:	Ionic conductances underlying excitability in tonically firing neurons (TFNs) from substantia gelatinosa (SG) were studied by the patch-clamp method in rat spinal cord slices. Ca(2+)-dependent K(+) (K(CA)) conductance sensitive to apamin was found to prolong the interspike intervals and stabilize firing evoked by a sustained membrane depolarization. Suppression of Ca(2+) and K(CA) currents, however, did not abolish the basic pattern of tonic firing, indicating that it was generated by voltage-gated Na(+) and K(+) currents. Na(+) and K(+) channels were further analyzed in somatic nucleated patches. Na(+) channels exhibited fast activation and inactivation kinetics and followed two-exponential time course of recovery from inactivation. The major K(+) current was carried through tetraethylammonium (TEA)-sensitive rapidly activating delayed-rectifier (K(DR)) channels with a slow inactivation. The TEA-insensitive transient A-type K(+) (K(A)) current was very small in patches and was strongly inactivated at resting potential. Block of K(DR) rather than K(A) conductance by 1 mM TEA lowered the frequency and stability of firing. Intracellular staining with biocytin revealed at least three morphological groups of TFNs. Finally, on the basis of present data, we created a model of TFN and showed that Na(+) and K(DR) currents are sufficient to generate a basic pattern of tonic firing. It is concluded that the balanced contribution of all ionic conductances described here is important for generation and modulation of tonic firing in SG neurons.
Tárgyszavak:	Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban külföldön készült közlemény
Megjelenés:	Journal of Neurophysiology. - 91 : 2 (2004), p. 646-655. -
További szerzők:	Santos, Sónia F. A. Szokol Karolina Szűcs Péter (1974-) (kutatóorvos) Safronov, Boris V.
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat
Borító:
Saját polcon:

001-es BibID:	BIBFORM029494
Első szerző:	Roberts, Alan
Cím:	Properties of networks controlling locomotion and significance of voltage dependency of NMDA channels : simulation study of rhythm generation sustained by positive feedback / Roberts A., Tunstall M. J., Wolf E.
Dátum:	1995
ISSN:	0022-3077
Megjegyzések:	We have built a realistic 24-neuron model based on data from the spinal pattern generator for swimming in Xenopus embryos with the use of the SWIM programs. The neurons have dendrite, soma, and axon compartments with voltage-gated Na+ and K+ channels. Dendritic synapses were modeled as modulated ionic conductances with currents that have different reversal levels. One of these conductances was voltage dependent to model N-methyl-D-aspartate ("NMDA") synapses in the presence of Mg2+. 2. In this model, rhythm generation is initiated by a brief excitation, depends on rebound from reciprocal inhibition, and is sustained by long-duration "NMDA-dependent" feedback excitation. 3. Without NMDA voltage dependency, rhythmic activity is stable over a wide range of synaptic conductances. Its frequency decreases with more inhibition and increases with more excitation. The introduction of normally distributed variation in soma size or excitatory synaptic conductance extends the lower stable frequency range. Without such variation the frequency of the 24-neuron model is the same as a 4-neuron model provided that the synaptic conductances for each neuron are the same. 4. The effect of introducing NMDA voltage dependency on rebound after negative current injections or synaptic inhibition was investigated in single depolarized model neurons. With NMDA voltage dependency, hyperpolarizations and rebound spike responses were increased. 5. Network activity with NMDA voltage dependency was similar to that without it, but inhibitory postsynaptic potentials (IPSPs) and spikes were larger, and frequencies were lower and more sensitive to changes in excitatory and inhibitory conductance. 6. We conclude that in the model, mutual reexcitation among excitatory spinal interneurons can sustain rhythm generation by positive feedback and that NMDA voltage dependency can enhance postinhibitory rebound, stabilize swimming activity and extend its lower frequency range, and steepen the dependency of frequency on synaptic drive.
Tárgyszavak:	Orvostudományok Természettudományok Biológiai tudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban külföldön készült közlemény
Megjelenés:	Journal Of Neurophysiology. - 73 : 2 (1995), p. 485-495. -
További szerzők:	Tunstall, Mark J. Wolf Ervin (1961-) (fizikus, neurobiológus)
Internet cím:	Intézményi repozitóriumban (DEA) tárolt változat
Borító:
Saját polcon: