Brain research bulletin
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Brain research bulletin · Feb 2003
Psychophysical and EEG responses to repeated experimental muscle pain in humans: pain intensity encodes EEG activity.
Clinical pain is often characterized by repetitive and persistent occurrence in deep structures, but few studies investigated repetitive tonic pain in humans. To determine cerebral responses to repetitive tonic pain, psychophysical responses, and electroencephalographic (EEG) activation to five trials of repeated tonic muscle pain induced by hypertonic saline were examined and analyzed in 13 male subjects. The study was composed of two experimental sessions performed in separate days. ⋯ Throughout five injections, the reduction of alpha-1 activity was contrary to the changes of pain intensity. These results indicates that pain-related EEG activities were encoded by the pain intensity. The thalamo-cortical system and descending inhibitory neuronal networks may be involved in the regulation of pain intensity.
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Brain research bulletin · Feb 2003
Electrical stimulation of thalamic Nucleus Submedius inhibits responses of spinal dorsal horn neurons to colorectal distension in the rat.
In 78 halothane-anesthetized rats, we characterized the responses of single neurons in the dorsal horn of L(6)-S(1) spinal segments to a noxious visceral stimulus (colorectal balloon distension, CRD), and studied the effects of focal electrical stimulation of Nucleus Submedius (Sm) on these responses using standard extracellular microelectrode recording techniques. A total of 102 neurons were isolated on the basis of spontaneous activity. Eighty (78%) responded to CRD, of which 70% had excitatory and 30% had inhibitory responses. ⋯ Sm stimulation produced facilitation of CRD responses of only one neuron (CRD-inhibited). Sm stimulation had no effects on spontaneous activity. These data indicate that Sm may be involved in the descending inhibitory modulation of visceral nociception at the spinal level.