title: The effects of periaqueductal gray and nucleus raphe magnus stimulation on the spontaneous and noxious-evoked activity of lateral reticular nucleus neurons in rabbits.
abstract: In urethane-anesthetized rabbits the effects of periaqueductal gray (PAG) and nucleus raphe magnus (NRM) stimulation on the spontaneous and noxious-evoked activity of the lateral reticular nucleus (LRN) neurons were studied. The PAG and the NRM stimulating electrodes were located in the optimal sites for suppressing the jaw-opening reflex (JOR) evoked by the tooth pulp stimulation. It was found that the 12% of neurons tested were affected by one or both stimuli. A total of 80 responsive neurons (52% antidromically activated by the cerebellum) were analyzed. Out of these neurons, 31 showed a convergence to both stimuli, 43 responded only to PAG and 6 only to NRM. Noxious heat stimulation of the contralateral foot was effective in altering the activity of 60% of these neurons. The PAG and NRM stimuli modified the noxious-evoked responses in most of these units. While the excitation was the predominant effect on the spontaneous activity (52 cells), the inhibition was predominant on the noxious-evoked activity (29 cells). These results indicate the presence of connections from PAG and NRM to LRN, probably devoted to the processing of the nociceptive information.
mesh_terms: D000200:Action Potentials; D000818:Animals; D004558:Electric Stimulation; D007568:Jaw / Q000502:physiology; D008526:Medulla Oblongata / Q000502:physiology*; D009433:Neural Inhibition; D009434:Neural Pathways / Q000502:physiology; D010146:Pain / Q000503:physiopathology*; D010487:Periaqueductal Gray / Q000502:physiology*; D011817:Rabbits; D011903:Raphe Nuclei / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012018:Reflex / Q000502:physiology