Excitatory and Inhibitory Electrodermal Reflexes Evoked by Cutaneous Stimulation in Acute Spinal Cats

Svensson, Peter, Satoshi Minoshima, Ahmad Beydoun, Thomas J. Morrow, and Kenneth L. Casey. Cerebral processing of acute skin and muscle pain in humans. J. Neurophysiol. 78: 450–460, 1997. The human cerebral processing of noxious input from skin and muscle was compared with the use of positron emission tomography with intravenous H2 15O to detect changes in regional cerebral blood flow (rCBF) as an indicator of neuronal activity. During each of eight scans, 11 normal subjects rated the intensity of stimuli delivered to the nondominant (left) forearm on a scale ranging from 0 to 100 with 70 as pain threshold. Cutaneous pain was produced with a high-energy CO2 laser stimulator. Muscle pain was elicited with high-intensity intramuscular electrical stimulation. The mean ratings of perceived intensity for innocuous and noxious stimulation were32.6 ± 4.5 (SE) and 78.4 ± 1.7 for cutaneous stimulation and 15.4 ± 4.2 and 73.5 ± 1.4 for intramuscular stimulation. The pain intensity ratings and the differences between noxious and innocuous ratings were similar for cutaneous and intramuscular stimuli ( P > 0.05). After stereotactic registration, statistical pixel-by-pixel summation ( Z score) and volumes-of-interest (VOI) analyses of subtraction images were performed. Significant increases in rCBF to both noxious cutaneous and intramuscular stimulation were found in the contralateral secondary somatosensory cortex (SII) and inferior parietal lobule [Brodmann area (BA) 40]. Comparable levels of rCBF increase were found in the contralateral anterior insular cortex, thalamus, and ipsilateral cerebellum. Noxious cutaneous stimulation caused significant activation in the contralateral lateral prefrontal cortex (BA 10/46) and ipsilateral premotor cortex (BA 4/6). Noxious intramuscular stimulation evoked rCBF increases in the contralateral anterior cingulate cortex (BA 24) and subsignificant responses in the contralateral primary sensorimotor cortex (MI/SI) and lenticular nucleus. These activated cerebral structures may represent those recruited early in nociceptive processing because both forms of stimuli were near pain threshold. Correlation analyses showed a negative relationship between changes in rCBF for thalamus and MI/SI for cutaneous stimulation, and positive relationships between thalamus and anterior insula for both stimulus modalities. Direct statistical comparisons between innocuous cutaneous and intramuscular stimulation with the use of Z scores and VOI analyses showed no reliable differences between these two forms of noxious stimulation, indicating a substantial overlap in brain activation pattern. The comparison of noxious cutaneous and intramuscular stimulation indicated more activation in the premotor cortex, SII, and prefrontal cortex with cutaneous stimulation, but these differences did not reach statistical significance. The similar cerebral activation patterns suggest that the perceived differences between acute skin and muscle pain are mediated by differences in the intensity and temporospatial pattern of neuronal activity within similar sets of forebrain structures.

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Raphe Magnus Neurons Help Protect Reactions to Visceral Pain From Interruption by Cutaneous Pain

Journal of Neurophysiology ◽

10.1152/jn.00793.2006 ◽

2006 ◽

Vol 96 (6) ◽

pp. 3423-3432 ◽

Cited By ~ 18

Author(s):

Thaddeus S. Brink ◽

Kevin M. Hellman ◽

Aaron M. Lambert ◽

Peggy Mason

Keyword(s):

Cellular Response ◽

Receptor Agonist ◽

Visceral Pain ◽

Noxious Stimulus ◽

Colorectal Distension ◽

Cutaneous Stimulation ◽

Cell Discharge ◽

Raphe Magnus ◽

Life Threatening ◽

On And Off Cells

Suppression of reactions to one noxious stimulus by a spatially distant noxious stimulus is termed heterotopic antinociception. In lightly anesthetized rats, a noxious visceral stimulus, colorectal distension (CRD), suppressed motor withdrawals but not blood pressure or heart rate changes evoked by noxious hindpaw heat. Microinjection of muscimol, a GABAA receptor agonist, into raphe magnus (RM) reduced CRD-evoked suppression of withdrawals, evidence that RM neurons contribute to this heterotopic antinociception. To understand how brain stem neurons contribute to heterotopic antinociception, RM neurons were recorded during CRD-elicited suppression of hindpaw withdrawals. Although subsets of RM neurons that were excited (on cells) or inhibited (off cells) by noxious cutaneous stimulation were either excited or inhibited by CRD, on cells were inhibited and off cells excited by an intracerebroventricularly administered opioid, evidence that the nociception-facilitating and -inhibiting functions of on and off cells, respectively, are predicted by the cellular response to noxious cutaneous stimulation alone and not by the response to CRD. When recorded during CRD-elicited antinociception, RM cell discharge resembled the pattern observed in response to CRD stimulation alone. However, when hindpaw withdrawal suppression was incomplete, RM cell discharge resembled the pattern observed in response to heat alone. We propose that on cells excited by CRD facilitate responses to CRD itself, which in turn augments excitation of off cells that then act to suppress cutaneous nociception. RM cells may thereby contribute to the dominance of quiet recuperative reactions evoked by potentially life-threatening visceral stimuli over transient somatomotor activity elicited by less-injurious noxious cutaneous stimuli.

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Circulatory reactions in the gastrointestinal tract elicited by localized cutaneous stimulation

American Heart Journal ◽

10.1016/s0002-8703(40)90533-6 ◽

1940 ◽

Vol 20 (6) ◽

pp. 743-749 ◽

Cited By ~ 18

Author(s):

Albert Kuntz ◽

L.Anson Haselwood

Keyword(s):

Gastrointestinal Tract ◽

Cutaneous Stimulation

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Red Nucleus Stimulation Inhibits Within the Inferior Olive

Journal of Neurophysiology ◽

10.1152/jn.1998.80.6.3127 ◽

1998 ◽

Vol 80 (6) ◽

pp. 3127-3136 ◽

Cited By ~ 14

Author(s):

K. M. Horn ◽

T. M. Hamm ◽

A. R. Gibson

Keyword(s):

Inferior Olive ◽

Red Nucleus ◽

Salient Feature ◽

Cutaneous Stimulation ◽

Motor Pathways ◽

Peripheral Stimulation ◽

Dorsal Columns ◽

Dorsolateral Funiculus ◽

Somatosensory Responses ◽

Stimulation Of

Horn, K. M., T. M. Hamm, and A. R. Gibson. Red nucleus stimulation inhibits within the inferior olive. J. Neurophysiol. 80: 3127–3136, 1998. In the anesthetized cat, electrical stimulation of the magnocellular red nucleus (RNm) inhibits responses of rostral dorsal accessory olive (rDAO) neurons to cutaneous stimulation. We tested the hypothesis that RNm-mediated inhibition occurs within the inferior olive by using stimulation of the ventral funiculus (VF) of the spinal cord in place of cutaneous stimulation of the hindlimb. Fibers in the VF terminate on hindlimb rDAO neurons, so inhibition of this input would have to occur within the olive. rDAO responses elicited by VF stimulation were inhibited by prior stimulation of the RNm, indicating that inhibition occurs within the olive. In contrast, evoked potentials recorded from the VF or dorsal columns following hindlimb stimulation were not affected by prior stimulation of RNm, indicating that stimulation of the RNm does not inhibit olivary afferents at spinal levels. RNm stimulation that inhibited rDAO responses had little effect on evoked somatosensory responses in thalamus, indicating that inhibition generated by activity in RNm may be specific to rDAO. To test limb specificity of RNm-mediated inhibition, conditioning stimulation was applied to the dorsolateral funiculus at thoracic levels, which selectively activates RNm neurons projecting to the lumbar cord. Stimulation at thoracic levels inhibited evoked responses from hindlimb but not forelimb regions of rDAO, suggesting that inhibitory effects of RNm activity are limb specific. Several studies have reported that olivary neurons have reduced sensitivity to peripheral stimulation during movement; it is likely that RNm-mediated inhibition occurring within the olive contributes to this reduction of sensitivity. Inhibition of rDAO responses by descending motor pathways appears to be a salient feature of olivary function.

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Cutaneous stimulation evokes long-lasting excitation of spinal interneurons in the turtle

Journal of Neurophysiology ◽

10.1152/jn.1990.64.4.1134 ◽

1990 ◽

Vol 64 (4) ◽

pp. 1134-1148 ◽

Cited By ~ 36

Author(s):

S. N. Currie ◽

P. S. Stein

Keyword(s):

Spinal Cord ◽

Receptive Field ◽

Action Potential ◽

Receptive Fields ◽

Neural Mechanisms ◽

Cutaneous Afferents ◽

Cutaneous Stimulation ◽

Single Action ◽

Single Action Potential ◽

Stimulation Of

1. We demonstrated multisecond increases in the excitability of the rostral-scratch reflex in the turtle by electrically stimulating the shell at sites within the rostral-scratch receptive field. To examine the cellular mechanisms for these multisecond increases in scratch excitability, we recorded from single cutaneous afferents and sensory interneurons that responded to stimulation of the shell within the rostral-scratch receptive field. A single segment of the midbody spinal cord (D4, the 4th postcervical segment) was isolated in situ by transecting the spinal cord at the segment's anterior and posterior borders. The isolated segment was left attached to its peripheral nerve that innervates part of the rostral-scratch receptive field. A microsuction electrode (4-5 microns ID) was used to record extracellularly from the descending axons of cutaneous afferents and interneurons in the spinal white matter at the posterior end of the D4 segment. 2. The turtle shell is innervated by slowly and rapidly adapting cutaneous afferents. All cutaneous afferents responded to a single electrical stimulus to the shell with a single action potential. Maintained mechanical stimulation applied to the receptive field of some slowly adapting afferents produced several seconds of afterdischarge at stimulus offset. We refer to the cutaneous afferent afterdischarge caused by mechanical stimulation of the shell as "peripheral afterdischarge." 3. Within the D4 spinal segment there were some interneurons that responded to a brief mechanical stimulus within their receptive fields on the shell with short afterdischarge and others that responded with long afterdischarge. Short-afterdischarge interneurons responded to a single electrical pulse to a site in their receptive fields either with a brief train of action potentials or with a single action potential. Long-afterdischarge interneurons responded to a single electrical shell stimulus with up to 30 s of afterdischarge. Long-afterdischarge interneurons also exhibited strong temporal summation in response to a pair of electrical shell stimuli delivered up to several seconds apart. Because all cutaneous afferents responded to an electrical shell stimulus with a single action potential, we conclude that electrically evoked afterdischarge in interneurons was produced by neural mechanisms in the spinal cord; we refer to this type of afterdischarge as "central afterdischarge." 4. These results demonstrate that neural mechanisms for long-lasting excitability changes in response to cutaneous stimulation reside in a single segment of the spinal cord. Cutaneous interneurons with long afterdischarge may serve as cellular loci for multise

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