Pain Descending Pathways: Difference between revisions
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== The descending pain modulatory system == | == The descending pain modulatory system == | ||
The "top down" modulation of pain has been in evidence since the early work of Sherrington<ref name="Sherrington" /> showing that nociceptive reflexes were enhanced after transection of the spinal cord. This was further elaborated on by Fields<ref name="Fields">Fields HL. Pain modulation: expectation, opoid analgesia and virtual pain. Prog Brain Res 122:245-253; 2000</ref> and Milan<ref name="Milan">Milan MJ. Descending control of pain. Prog Neurobiology 66:355-474; 2002</ref> who, based upon observations in the 1960's that electrical stimuation of the periaqueductal gray (PAG) area can produce analgesia, demostrated through electrophysiological and pharmacological studies that descending influences on spinal nociceptive processing involves the PAG and the rostral ventronedial medulla (RVM). | The ''"top down"'' modulation of pain has been in evidence since the early work of Sherrington<ref name="Sherrington" /> showing that nociceptive reflexes were enhanced after transection of the spinal cord. This was further elaborated on by Fields<ref name="Fields">Fields HL. Pain modulation: expectation, opoid analgesia and virtual pain. Prog Brain Res 122:245-253; 2000</ref> and Milan<ref name="Milan">Milan MJ. Descending control of pain. Prog Neurobiology 66:355-474; 2002</ref> who, based upon observations in the 1960's that electrical stimuation of the periaqueductal gray (PAG) area can produce analgesia, demostrated through electrophysiological and pharmacological studies that descending influences on spinal nociceptive processing involves the PAG and the rostral ventronedial medulla (RVM). | ||
Work by Hadjipavlou et al<ref name="Hadjipavlou">Hadjipavlou G, Dunckley P, Behrens TE, Tracey I. Determining anatomical connectives between cortical and brainstem pain processing regions in humans: a diffusion tensor imaging study in healthy controls. Pain 123: 169-178; 2006</ref> used functional and anatomical studies to link the descending pain modulatory system from the brain stem (where the PAG and RVM reside) to a number of higher level brain area including; cingulofrontal regions, the amygdalae and the hypothalamus (figure 1). This may go someway to help explain the role that emotions and cognition have in processing nociceptive information. | Work by Hadjipavlou et al<ref name="Hadjipavlou">Hadjipavlou G, Dunckley P, Behrens TE, Tracey I. Determining anatomical connectives between cortical and brainstem pain processing regions in humans: a diffusion tensor imaging study in healthy controls. Pain 123: 169-178; 2006</ref> used functional and anatomical studies to link the descending pain modulatory system from the brain stem (where the PAG and RVM reside) to a number of higher level brain area including; cingulofrontal regions, the amygdalae and the hypothalamus (figure 1). This may go someway to help explain the role that emotions and cognition have in processing nociceptive information. | ||
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Underpinning the descending pain modulatory system is the endogenous opoid system<ref name="Akil">Akil H, Watson SJ, Young E, Lewis ME, Khachaturian H, Walker JM. Endogenous opioids: biology and function. Annu Rev Neurosci 7: 223-255; 1984</ref> and according to Willer<ref name="Willer">Willer JC, Dehen H, Cambier J. Stress induced analgesia in humans: endogenous opiods and naloxone-reversible depression of pain reflexes. Science 212:689-691; 1981</ref> this system may be activated by a variety of reflex and cognitively trigged states. At the spinal cord (dorsal horn), level the opiod system causes inhibition of substance P from peripheral noxious mechanical stimulation<ref name="Kuraishi">Kuraishi, Y. Neuropeptide-mediated transmission of nociceptive information and its regulation. Novel mechanisms of analgesics. Yakugaku Zasshi 2008; 110(10),711-772</ref> via release of noradrenaline from the dorsalateral PAG (dPAG) and thermal nociceptive stimuli via the release of serotonin from the ventrolateral PAG (vPAG)<ref name="Kuraishi 1983">Kuraishi Y, Harada Y, Aratani S. Seperate involvement of the spinal noradrenergic and serotonergic systems in morphine analgesia: the differences in mechanical and thermal algesic tests. Brain Res 1983;273, 245-252</ref>. | |||
Underpinning the descending pain modulatory system is the endogenous opoid system<ref name="Akil">Akil H, Watson SJ, Young E, Lewis ME, Khachaturian H, Walker JM. Endogenous opioids: biology and function. Annu Rev Neurosci 7: 223-255; 1984</ref> and according to Willer<ref name="Willer">Willer JC, Dehen H, Cambier J. Stress induced analgesia in humans: endogenous opiods and naloxone-reversible depression of pain reflexes. Science 212:689-691; 1981</ref> this system may be activated by a variety of reflex and cognitively trigged states. At the spinal cord, level the opiod system causes inhibition of substance P from peripheral noxious mechanical stimulation<ref name="Kuraishi">Kuraishi, Y. Neuropeptide-mediated transmission of nociceptive information and its regulation. Novel mechanisms of analgesics. Yakugaku Zasshi 2008; 110(10),711-772</ref> via release of noradrenaline from the dorsalateral PAG (dPAG) and thermal nociceptive stimuli via the release of serotonin from the ventrolateral PAG (vPAG)<ref name="Kuraishi 1983">Kuraishi Y, Harada Y, Aratani S. Seperate involvement of the spinal noradrenergic and serotonergic systems in morphine analgesia: the differences in mechanical and thermal algesic tests. Brain Res 1983;273, 245-252</ref>. | |||
== The role of the brain stem == | == The role of the brain stem == | ||
Revision as of 14:03, 10 September 2014
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The descending pain modulatory system[edit | edit source]
The "top down" modulation of pain has been in evidence since the early work of Sherrington[1] showing that nociceptive reflexes were enhanced after transection of the spinal cord. This was further elaborated on by Fields[2] and Milan[3] who, based upon observations in the 1960's that electrical stimuation of the periaqueductal gray (PAG) area can produce analgesia, demostrated through electrophysiological and pharmacological studies that descending influences on spinal nociceptive processing involves the PAG and the rostral ventronedial medulla (RVM).
Work by Hadjipavlou et al[4] used functional and anatomical studies to link the descending pain modulatory system from the brain stem (where the PAG and RVM reside) to a number of higher level brain area including; cingulofrontal regions, the amygdalae and the hypothalamus (figure 1). This may go someway to help explain the role that emotions and cognition have in processing nociceptive information.
Underpinning the descending pain modulatory system is the endogenous opoid system[5] and according to Willer[6] this system may be activated by a variety of reflex and cognitively trigged states. At the spinal cord (dorsal horn), level the opiod system causes inhibition of substance P from peripheral noxious mechanical stimulation[7] via release of noradrenaline from the dorsalateral PAG (dPAG) and thermal nociceptive stimuli via the release of serotonin from the ventrolateral PAG (vPAG)[8].
The role of the brain stem[edit | edit source]
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Neurochemical underpinnings[edit | edit source]
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References[edit | edit source]
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- ↑ Cite error: Invalid
<ref>tag; no text was provided for refs namedSherrington - ↑ Fields HL. Pain modulation: expectation, opoid analgesia and virtual pain. Prog Brain Res 122:245-253; 2000
- ↑ Milan MJ. Descending control of pain. Prog Neurobiology 66:355-474; 2002
- ↑ Hadjipavlou G, Dunckley P, Behrens TE, Tracey I. Determining anatomical connectives between cortical and brainstem pain processing regions in humans: a diffusion tensor imaging study in healthy controls. Pain 123: 169-178; 2006
- ↑ Akil H, Watson SJ, Young E, Lewis ME, Khachaturian H, Walker JM. Endogenous opioids: biology and function. Annu Rev Neurosci 7: 223-255; 1984
- ↑ Willer JC, Dehen H, Cambier J. Stress induced analgesia in humans: endogenous opiods and naloxone-reversible depression of pain reflexes. Science 212:689-691; 1981
- ↑ Kuraishi, Y. Neuropeptide-mediated transmission of nociceptive information and its regulation. Novel mechanisms of analgesics. Yakugaku Zasshi 2008; 110(10),711-772
- ↑ Kuraishi Y, Harada Y, Aratani S. Seperate involvement of the spinal noradrenergic and serotonergic systems in morphine analgesia: the differences in mechanical and thermal algesic tests. Brain Res 1983;273, 245-252
