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Paradoxical firing of thalamic neurons under neuropathic pain state in rats.

AbstractOBJECTIVES:
A novel evaluative approach was used to determine single unit activities of non-bursting intralaminar thalamic nuclei under neuropathic pain state following dorsal rhizotomy.
SETTINGS AND DESIGN:
Extensive dorsal rhizotomy at cervicothoracic level in rats was used as a model of central pain. After rhizotomy, rats were divided into two groups: rats without any signs of self-mutilation, and those presenting self-mutilation. Spontaneous single unit activities of neurons of intralaminar thalamic nuclei were recorded and interspike intervals (ISIs) of non-bursting cells were counted for both groups and compared with that of non-rhizotomized control rats. Chaodynamic methods were applied for the evaluation of the ISIs.
RESULTS:
In control rats Lyapunov exponents, Shannon entropy and mutual information average values were significantly higher than those of rhizotomized rats without any signs of self-mutilation. Paradoxically, in animals presenting self-mutilation following rhizotomy the evaluated parameters were similar to those of controls. Further, Lyapunov exponents were positive values in all animals indicating chaotic pattern of the neuronal firing.
MAIN FINDINGS:
1. Neurons behave in chaotic way in all animals, 2. The most regular firing was found in non-mutilating rhizotomized animals, 3. Patterns of the firing in selfmutilating rats were similar to those in controls.
CONCLUSIONS:
It is concluded that pain feeling is not executed neither by changes of chaotic dynamics of non-bursting intralaminar thalamic neurons. On the other hand, the paradoxical firing of the neurons under pathological brain matrix might participate in modification pain feeling.
AuthorsSimon Vaculin, Miloslav Franek, Ladislav Andrey, Richard Rokyta
JournalNeuro endocrinology letters (Neuro Endocrinol Lett) Vol. 25 Issue 6 Pg. 407-10 (Dec 2004) ISSN: 0172-780X [Print] Sweden
PMID15665800 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Topics
  • Action Potentials
  • Animals
  • Entropy
  • Intralaminar Thalamic Nuclei (physiology)
  • Male
  • Models, Neurological
  • Neuralgia (physiopathology)
  • Nonlinear Dynamics
  • Rats
  • Rats, Wistar
  • Rhizotomy

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