Pathways mediating descending control of spinal nociceptive transmission from the nuclei locus coeruleus (LC) and raphe magnus (NRM) in the cat

1986 ◽  
Vol 61 (3) ◽  
Author(s):  
S.S. Mokha ◽  
J.A. McMillan ◽  
A. Iggo
Keyword(s):  
Locus Coeruleus ◽  
Nociceptive Transmission ◽  
Raphe Magnus ◽  
Descending Control

scholarly journals Physiological Properties of Raphe Magnus Neurons During Sleep and Waking

1999 ◽  
Vol 81 (2) ◽  
pp. 584-595 ◽  
Author(s):  
Cynthia G. Leung ◽  
Peggy Mason
Keyword(s):  
Slow Wave ◽  
Slow Wave Sleep ◽  
Noxious Heat ◽  
Somatosensory Stimulation ◽  
Nociceptive Transmission ◽  
Cell Discharge ◽  
Descending Modulation ◽  
State Dependent ◽  
Physiological Properties ◽  
Raphe Magnus

Physiological properties of raphe magnus neurons during sleep and waking. Neurons in the medullary raphe magnus (RM) that are important in the descending modulation of nociceptive transmission are classified by their response to noxious tail heat as on,off, or neutral cells. Experiments in anesthetized animals demonstrate that RM on cells facilitate and off cells inhibit nociceptive transmission. Yet little is known of the physiology of these cells in the unanesthetized animal. The first aim of the present experiments was to determine whether cells with on- and off-like responses to noxious heat exist in the unanesthetized rat. Second, to determine if RM cells have state-dependent discharge, the activity of RM neurons was recorded during waking and sleeping states. Noxious heat applied during waking and slow wave sleep excited one group of cells (on-u) in unanesthetized rats. Other cells were inhibited by noxious heat (off-u) applied during waking and slow wave sleep states in unanesthetized rats. Neutral-u cells did not respond to noxious thermal stimulation applied during either slow wave sleep or waking. On-u and off-u cells were more likely to respond to noxious heat during slow wave sleep than during waking and were least likely to respond when the animal was eating or drinking. Although RM cells rarely respond to innocuous stimulation applied during anesthesia, on-u andoff-u cells were excited and inhibited, respectively, by innocuous somatosensory stimulation in the unanesthetized rat. The spontaneous activity of >90% of the RM neurons recorded in the unanesthetized rat was influenced by behavioral state. Off-u cells discharged sporadically during waking but were continuously active during slow wave sleep. By contrast,on-u and neutral-u cells discharged in bursts during waking and either ceased to discharge entirely or discharged at a low rate during slow wave sleep. We suggest that off cell discharge functions to suppress pain-evoked reactions during sleep, whereas on cell discharge facilitates pain-evoked responses during waking.

Changes in the effects of stimulation of locus coeruleus and nucleus raphe magnus following dorsal rhizotomy

1983 ◽  
Vol 288 (1-2) ◽  
pp. 325-329 ◽  
Author(s):  
Charles J. Hodge ◽  
A. Vania Apkarian ◽  
Michael P. Owen ◽  
Brian S. Hanson
Keyword(s):  
Locus Coeruleus ◽  
Nucleus Raphe Magnus ◽  
Dorsal Rhizotomy ◽  
Raphe Magnus ◽  
Stimulation Of

scholarly journals Serotonergic Raphe Magnus Cells That Respond to Noxious Tail Heat Are Not on or off Cells

2000 ◽  
Vol 84 (4) ◽  
pp. 1719-1725 ◽  
Author(s):  
Keming Gao ◽  
Peggy Mason
Keyword(s):  
Neuronal Response ◽  
Stimulus Onset ◽  
Thermal Stimulation ◽  
Evoked Responses ◽  
Noxious Heat ◽  
Nociceptive Transmission ◽  
Raphe Magnus ◽  
Pharmacological Studies ◽  
Excitatory Responses ◽  
Serotonin Immunoreactivity

Pharmacological studies have suggested that serotonergic cells in RM contribute to both the inhibition and facilitation of spinal nociceptive transmission. Physiological studies in the medullary nucleus raphe magnus (RM) and adjacent nucleus reticularis magnocellularis have identified putative nociceptive-inhibitory off cells and nociceptive-facilitatory neurons on cells by their responses to noxious thermal stimulation. The present study was designed to determine 1) whether any serotonergic RM cells respond to noxious thermal stimulation and 2) whether noxious heat-responsive serotonergic cells should be classified ason or off cells. Serotonergic cells ( n = 150) were identified by physiological criteria in anesthetized rats; 30 of 32 cells tested contained serotonin immunoreactivity. Noxious tail heat elicited a neuronal response in less than a quarter of the serotonergic cells. Most serotonergic cells that responded to tail heat were excited ( n = 25), while a small minority of the cells tested were inhibited ( n = 8). The tail heat-evoked responses of serotonergic cells were small in magnitude, averaging five to eight spikes in 10 s. Excitatory responses rarely persisted for more than 10 s, while inhibitory responses rarely persisted for more than 20 s. The tail heat-evoked responses of serotonergic cells were compared to those of non-serotonergic cells ( n = 186). Non-serotonergic cells that responded to noxious tail heat had significantly greater response magnitudes, averaging 75–95 spikes in 10 s, than heat-responsive serotonergic cells. In addition, most heat-responsive non-serotonergic cells responded for at least 30 s after stimulus onset. These results demonstrate that the tail heat-evoked responses of serotonergic RM cells are qualitatively and quantitatively distinct from those of non-serotonergic onand off cells. It is therefore unlikely that serotonergic RM cells, even the subpopulation that responds to noxious tail heat, share a physiological function with on and offcells.

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