Striatal inhibition of nociceptive responses evoked in trigeminal sensory neurons by tooth pulp stimulation.
The noxious evoked response in trigeminal sensory neurons was studied to address the role of striatum in the control of nociceptive inputs. In urethane-anesthetized rats, the jaw opening reflex (JOR) was produced by suprathreshold stimulation of the tooth pulp and measured as electromyographic response in the digastric muscle, with simultaneous recording of noxious responses in single unit neurons of the spinal trigeminal nucleus pars caudalis (Sp5c). The microinjection of glutamate (80 etamol/0.5 microl) into striatal JOR inhibitory sites significantly decreased the A delta and C fiber-mediated-evoked response (53 +/- 4.2 and 43.6 +/- 6.4% of control value, P < 0.0001) in 92% (31/34) of nociceptive Sp5c neurons. The microinjection of the solvent was ineffective, as was microinjection of glutamate in sites out of the JOR inhibitory ones. In another series of experiments, simultaneous single unit recordings were performed in the motor trigeminal nucleus (Mo5) and the Sp5c nucleus. Microinjection of glutamate decreased the noxious-evoked response in Sp5c and Mo5 neurons in parallel with the JOR, without modifying spontaneous neuronal activity of trigeminal motoneurons (n = 8 pairs). These results indicate that the striatum could be involved in the modulation of nociceptive inputs and confirm the role of the basal ganglia in the processing of nociceptive information.
Belforte
Juan E
JE
Laboratorio de Neurofisiología, Deptartamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155, Buenos Aires 1121, Argentina.
Pazo
Jorge H
JH
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D000704:Analysis of Variance; D000818:Animals; D016009:Chi-Square Distribution; D003342:Corpus Striatum / Q000187:drug effects / Q000502:physiology*; D003782:Dental Pulp / Q000294:innervation* / Q000528:radiation effects; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D018698:Glutamic Acid / Q000494:pharmacology; D007568:Jaw / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D008297:Male; D008845:Microinjections / Q000379:methods; D018482:Muscle, Skeletal / Q000502:physiology / Q000528:radiation effects; D009281:Naphthalenes; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D009433:Neural Inhibition / Q000502:physiology* / Q000528:radiation effects; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D009619:Nociceptors / Q000502:physiology*; D010082:Oxepins; D010812:Physical Stimulation / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D012018:Reflex / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D014279:Trigeminal Nucleus, Spinal / Q000166:cytology*
C461941:1-phenyl-1,4-epoxy-1H,4H-naphtho(1,8-de)(1,2)dioxepin; D009281:Naphthalenes; D010082:Oxepins; D018698:Glutamic Acid