Doctoral Thesis
DOI
https://doi.org/10.11606/T.5.2007.tde-28012008-092511
Document
Author
Full name
Erich Talamoni Fonoff
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2007
Supervisor
Committee
Teixeira, Manoel Jacobsen (President)
Barbosa, Egberto Reis
Chadi, Gerson
Hamani, Clement
Yeng, Lin Tchia
Title in Portuguese
Efeitos da estimulação elétrica do córtex motor na modulação da dor: análise comportamental e eletrofisiológica em ratos
Keywords in Portuguese
Comportamento
Córtex motor/fisiologia
Dor
Estimulação elétrica
Modelos animais
Neurônios
Potenciais de ação
Tálamo
Abstract in Portuguese
Introdução. Nos últimos a função motora vem sendo associada com a atenuação sensitiva e de dor, logo antes, durante e apos a contração muscular. No entanto as vias anatômicas e funcionais deste fenômeno não são conhecidas. O objetivo deste estudo é o de criar um modelo animal e investigar o efeito da estimulação subliminar do córtex motor (ECM) no limiar nociceptivo e na atividade neuronal subcortical. Método. O limiar nociceptivo foi avaliado por teste plantar e reflexo de retirada da cauda antes e após o implante dos eletródios epidurais sobre o córtex motor da pata posterior orientado por mapa funcional na mesma cepa de ratos. Os mesmos testes foram repetidos antes, durante e após a ECM. Antagonismo sistêmico do por naloxona foi incluído neste protocolo para investigar a relação com mediação opióide. O registro neuronal multiunitário do núcleo centro mediano (CM) e ventral posterolateral (VPL) do tálamo e da substância periaqüeductal (SPM) foi realizado antes, durante e após ECM ipso e contralateral. Resultados. O implante per se não causou alterações no limiar nociceptivo. ECM induziu significativa antinocicepção seletiva na pata contralateral mas não na ipsolateral. Este efeito não mais foi observado 15 minutos após o término da estimulação. Nenhuma alteração motora e comportamental foi observada nos testes de campo aberto. A mesma estimulação no córtex sensitivo e parietal posterior não causou quaisquer alterações de limiar nociceptivo. Administração sistêmica de naloxone reverteu completamente o efeito antes observado com a ECM. O registro neuronal multiunitário evidenciou diminuição na atividade do CM durante e após a ECM contra e ipsolateral. O ritmo de disparos neuronais no VPL também mostrou diminuição apenas com a ECM ipsolateral. No entanto os neurônios da SPM aumentaram significativamente a freqüência de disparos com ECM ipsolateral e não com a contralateral. Conclusão. A ECM subliminar está relacionada consistentemente com a atenuação sensitiva durante o comportamento, provavelmente mediado por inibição talâmica e ativação da SPM.
Title in English
Effects of electrical stimulation of motor cortex on pain modulation: behavior and electrophysiological study in rats.
Keywords in English
Action potentials
Animal models.
Behavior
Electrical stimulation
Motor cortex/physiology
Neurons
Pain
Thalamus
Abstract in English
Background. The motor function has been associated to sensory and pain attenuation, before during and shortly after the muscle activity. How ever the anatomical and functional basis of this phenomenon is not yet defined. The present study was designed to set an animal model and investigate the effect of subthreshold electrical stimulation of motor cortex (MCS) on pain threshold and neuron activity of thalamus and periaqüedutal gray. Method. Nociceptive thresholds of hind paws and the tail flick reflex were evaluated before and after surgical placement of epidural electrodes; before during and after electrical stimulation of motor cortex. Opioid antagonism was also included in this protocol in order to define neurotransmitter mediation of this process. Multiunit recording of thalamic median center (CM) and ventral posterolateral nuclei (VPL) and lateral periaqüedutal gray (SPM) were performed before and after electrical stimulation of ipso and contralateral motor cortex. Results. The procedure itself did not induce any threshold changes. MCS induced selective antinociception of contralateral paw, but no changes were detected in the nociceptive threshold of the ipsolateral side. This effect disappeared completely 15 minutes after the stimulation was ceased. No behavioral or motor impairment were observed during and after the stimulation session in the open field test. The same stimulation on sensory and posterior parietal cortex did not elicit any changes in behavioral and nociceptive tests. Systemic administration of naloxone completely reversed the previous observed antinociceptive effect. Multiunit recording evidenced decrease in spontaneous neuron firing in CM with short recovery time during ipso and contralateral MCS. Neuron activity in VPL was also significantly decreased during ipsolateral MCS but not with contralateral stimulation. How ever, neuron firing in SPM was significantly increased during and long after ipsolateral MCS but not with contralateral stimulation. Conclusion. Subthreshold MCS is consistently related to sensory attenuation during behavior, probably through thalamic inhibition and SPM activation.
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Publishing Date
2008-01-28
WARNING: The material described below relates to works resulting from this thesis or dissertation. The contents of these works are the author's responsibility.
- FONOFF, E.T., et al. Antinociception induced by epidural motor cortex stimulation in naive conscious rats is mediated by the opioid system [doi:10.1016/j.bbr.2008.07.027]. Behavioral Brain Research [online], 2009, vol. 196, n. 1, p. 63-70.
- FONOFF, E.T., et al. Functional mapping of the motor cortex of the rat using transdural electrical stimulation [doi:10.1016/j.bbr.2009.03.018]. Behavioral Brain Research [online], 2009, vol. 202, n. 1, p. 138-141.