| 1. |
- Kalliomäki, Jarkko, et al.
(författare)
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Intrathecally applied morphine inhibits nociceptive C fiber input to the primary somatosensory cortex (SI) of the rat
- 1998
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Ingår i: Pain. - 0304-3959. ; 77:3, s. 323-329
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Tidskriftsartikel (refereegranskat)abstract
- Nociceptive C fiber input to SI in the halothane-nitrous oxide anesthetized rat was assessed by recording cortical field potentials evoked by noxious thermal cutaneous stimulation with CO2-laser pulses. Morphine topically applied onto the lumbar spinal cord produced a dose-dependent inhibition of nociceptive C fiber input from the hind paw to the contralateral SI. The inhibitory effect of morphine was reversed by naloxone. Potentials evoked by CO2-laser stimulation of the forepaw were unaffected by morphine applied on the lumbar cord, indicating that the effect of morphine was exerted at the segmental level. It is concluded that input from nociceptive C fibers to SI is relayed in the spinal cord and can be inhibited by spinal opioid receptor activation. The present method offers an interesting model of ascending nociceptive transmission to the cerebral cortex. Copyright (C) 1998 International Association for the Study of Pain. Published by Elsevier Science B.V.
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| 2. |
- Kalliomäki, Jarkko, et al.
(författare)
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Multiple spinal pathways mediate cutaneous nociceptive C-fibre input to the primary somatosensory cortex (SI) in the rat.
- 1993
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Ingår i: Brain Research. - 1872-6240. ; 622:1-2, s. 271-279
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, partial lesions of the lower thoracic spinal cord in rats anaesthetized with halothane and nitrous oxide were made in order to elucidate which of the spinal funiculi mediate a nociceptive C fibre input to SI. Field potentials evoked by noxious CO2-laser stimulation were recorded in the left SI. Nociceptive C fibre input from the right hindpaw to SI was propagated by the dorsal funiculi (DF) and the left and right lateral funiculi (LLF and RLF, respectively). Nociceptive C fibre input from the left hindpaw was propagated by LLF and RLF, but not DF. Input from the hindpaws mediated by LLF and RLF caused widespread surface positive potentials throughout most of SI, although potentials in the hindlimb area tended to be larger than those in other areas of SI. Input from the right hindpaw mediated by DF caused surface positive potentials mainly in the hindlimb area of SI. Intracortically, the field potentials reversed polarity in the superficial laminae and had maximal negative amplitudes in laminae III-IV (input transferred by DF and LLF) and in laminae V-VI (input transferred by LLF and RLF). It is concluded that there are multiple spinal pathways which can transfer information from cutaneous nociceptive C fibres to SI in the rat. These ascending pathways seem to activate partly different thalamo-cortical systems.
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| 3. |
- Kalliomäki, Jarkko, et al.
(författare)
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Nociceptive C fibre input to the primary somatosensory cortex (SI). A field potential study in the rat.
- 1993
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Ingår i: Brain Research. - 1872-6240. ; 622:1-2, s. 262-270
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, noxious thermal stimulation of the skin with short pulses of CO2-laser radiation was used to identify a cutaneous nociceptive C fibre input to SI and investigate the organization of this input in halothane-nitrous oxide anaesthetized rats. Noxious CO2-laser stimulation of the glabrous skin of the hindpaw consistently evoked late surface positive field potentials in SI (average onset latency 226 ms, peak latency 296 ms). It was demonstrated that these late potentials were evoked by an input from nociceptive C fibres, using a combination of latency measurements, anodal block of A fibre conduction and graded intensities of stimulation. Compared to the tactile evoked potentials in SI, the nociceptive C fibre evoked potentials were more widespread and exhibited a crude somatotopical organization. Intracortically, both tactile and nociceptive C fibre evoked potentials reversed polarity and exhibited a peak negativity in laminae III-IV. The nociceptive C fibre evoked potentials exhibited an additional peak negativity in laminae V-VI. The latter potential had a different time course as compared to the nociceptive C fibre potential evoked in laminae III-IV. In conclusion, an input from cutaneous nociceptive C fibres to SI was demonstrated for the first time in animal experiments. The input to SI from tactile receptors and cutaneous C nociceptors were differently organized.
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| 4. |
- Kalliomäki, Jarkko, et al.
(författare)
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Spinal NMDA-receptor dependent amplification of nociceptive transmission to rat primary somatosensory cortex (SI).
- 2003
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Ingår i: Pain. - 1872-6623. ; 104:1-2, s. 195-200
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Tidskriftsartikel (refereegranskat)abstract
- The role of NMDA mechanisms in spinal pathways mediating acute nociceptive input to the somatosensory cortex is not clear. In this study, the effect of NMDA-antagonists on nociceptive C fibre transmission to the primary somatosensory cortex (SI) was investigated. Cortical field potentials evoked by CO2-laser stimulation of the skin were recorded in the halothane/nitrous oxide anaesthetized rat. The SI nociceptive evoked potential (EP) amplitudes were dependent on the frequency of noxious heat stimulation. The amplitudes of SI potentials evoked by CO2-laser pulses (duration 15–20 ms, stimulation energy 21–28 mJ/mm2) delivered at a frequency of 0.1 Hz were approximately 40% of the amplitudes of potentials evoked by 1.0 Hz stimulation. After intrathecal lumbar application of either of the NMDA-antagonists CPP or MK-801, the amplitudes of nociceptive SI potentials, evoked by 1.0 Hz stimulation of the contralateral hindpaw, were reduced to approximately 40% of controls. By contrast, field potentials evoked by 0.1 Hz stimulation of the hindpaw were unaffected by MK-801. SI potentials evoked by 1.0 Hz stimulation of the contralateral forepaw did not change after lumbar application of CPP or MK-801, indicating that the depression of hindpaw EPs was due to a segmental effect in the spinal cord. It is concluded that spinal NMDA-receptor mechanisms amplify the acute transmission of nociceptive C fiber input to SI in a frequency-dependent way.
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