DRt neuron model (Sousa et al., 2014)

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Despite the importance and significant clinical impact of understanding information processing in the nociceptive system, the functional properties of neurons in many parts of this system are still unknown. In this work we performed whole-cell patch-clamp recording in rat brainstem blocks to characterize the electrophysiological properties of neurons in the dorsal reticular nucleus (DRt), a region known to be involved in pronociceptive modulation. We also compared properties of DRt neurons with those in the adjacent parvicellular reticular nucleus (PCRt) and in neighboring regions outside the reticular formation. We found that neurons in the DRt and PCRt had similar electrophysiological properties and exhibited mostly tonic-like firing patterns, whereas neurons outside the reticular formation showed a larger diversity of firing-patterns. The dominance of tonic neurons in the DRt supports previous conclusions that these neurons encode stimulus intensity through their firing frequency.
1 . Sousa M, Szucs P, Lima D, Aguiar P (2014) The pronociceptive dorsal reticular nucleus contains mostly tonic neurons and shows a high prevalence of spontaneous activity in block preparation. J Neurophysiol 111:1507-18 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Neuron or other electrically excitable cell;
Brain Region(s)/Organism:
Cell Type(s): Hodgkin-Huxley neuron;
Channel(s): I Na,t; I K; I K,Ca; I Calcium;
Gap Junctions:
Simulation Environment: NEURON;
Model Concept(s): Activity Patterns;
Implementer(s): Aguiar, Paulo [pauloaguiar at fc.up.pt];
Search NeuronDB for information about:  I Na,t; I K; I K,Ca; I Calcium;
These are the NEURON files for modelling a tonic neuron from the
Dorsal Reticular Nucleus (DRt), based on the experimental voltage
traces.  This model was used for:

1) recreating the firing properties of DRt neurons; 
2) studying the possible membrane currents giving rise to the
after-hyperpolarization variability observed experimentally;
3) exploring the mechanisms shaping the membrane potential histograms
under spontaneous activity conditions.

The Hodgkin-Huxley formalism was used to describe the ionic currents
present in the model: a persistent sodium current (INa), a
delayed-rectifier potassium current (IKdr), a voltage dependent
calcium current (ICa, L-type high threshold), and a calcium activated
potassium current (IK,Ca, or IAHP given its role in shaping the

The model also included a description for the internal calcium
concentration dynamics.  Synapses were modelled using dual exponential
conductance profiles and were introduced for the sole purpose of
introducing and analysing the contribution of membrane
fluctuations. The parametrization of the synaptic inputs was set in
order to produce a zero net change in membrane potential.  Stochastic
network activity was simulated by adding random excitatory and
inhibitory synaptic inputs with predefined mean times.  Membrane
potential fluctuations were generated by injecting normally
distributed current noise to the neuron model.

This model is described in:

Sousa M., Szucs P, Lima D. and Aguiar P.  "The pronociceptive dorsal
reticular nucleus contains mostly tonic neurons and shows a high
prevalence of spontaneous activity in block preparation". Accepted at
Journal of Neurophysiology, January 2014.

Core model parameters are specified in the Appendix section.

Mafalda Sousa and Paulo Aguiar
contact email: mafsousa@ibmc.up.pt and pauloaguiar@fc.up.pt

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