How two sites in the rat's nucleus raphe magnus interact to inhibit the tail-flick reflex.
Two stimulating microelectrodes were inserted 0.5 mm apart in the rat's nucleus raphe magnus (NRM), giving a joint electrical threshold for suppression of the heat-evoked tail-flick reflex. Synchronous stimulation often required more current than predicted by consideration of each site's solitary threshold. Asynchronous stimulation required yet more current. We postulate that some NRM cells, perhaps corresponding to the 'on-cells' found previously by microelectrode recording, facilitate flexion and become relatively more influential at higher stimulus currents. We also postulate that the dominating cells that suppress flexion, possibly 'off-cells', operate optimally when firing simultaneously.
Hentall
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Department of Physiology and Biophysics, University of Puerto Rico, San Juan 00936.
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D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D004558:Electric Stimulation; D006358:Hot Temperature; D008297:Male; D008959:Models, Neurological; D009475:Neurons, Afferent / Q000502:physiology*; D010146:Pain / Q000503:physiopathology*; D011903:Raphe Nuclei / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains; D012018:Reflex / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology; D013623:Tail / Q000294:innervation