Demostración y caracterización in silico del fenómeno de resonancia estocástica en sinapsis nociceptivas del tipo NMDA del asta dorsal medular.

Aim: nociceptive primary afferents establish synapses in the spinal dorsal horn (SDH) expressing mainly glutamatergic strongly excitatory NMDA type ionotropic channels. SDH postsynaptic neurons generate discharges inmersed in different noise levels which is classically considerated a signal transmission adverse factor. Material and method: in the present study, the effects of different noise levels (NL) was evaluated on a experimentally described model of NMDA type synapse between nociceptive SDH neurons. Pre and postsinaptic number of spikes, interspike intervals (ISI) and the post/presynaptic spike quotient were studied with a neuronal network simulator (Neurosim: Network v 1.2a.). The NL was progresssively increased (0 to ±5mV) in both spontaneous activity and evoked by a electrical stimulus (pulse ±29nA). Results: It was found a proportional increase of synaptic efficiency with NL with a logaríthmic function: Post/Pre Spike Quotient = 3,38+0,26NL- 0,029NL² (r=+0,67; P<0,05), the ISI for presynaptic: ISI = 14,33- 1,33NL+0,06NL² but also postsynaptic: ISI= 6,66- 0,85NL+0,06NL² showed a proportional decrease with NL (r=-0,72 and r=-0,79; respectively P<0,05). Conclusion: these results strongly suggest, for the first time, that the NL increases the synaptic efficiency in the model of NMDA type synapse between nociceptive SDH neurons, this phenomenon of interest in nociception, named stochastic resonance, was described first in others places of the central nervous system. [ABSTRACT FROM AUTHOR]