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The heterosegmentally activated slow positive cord dorsum potential
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WHICH SPINAL NOCICEPTIVE NEURONS ARE CAPABLE OF MEDIATING SYMPATHETICALLY MAINTAINED PAIN? W.J.Roberts & M.E. Foglesong*, Neurological Sciences Institute, Good Samaritan.Hospital and Medical Center, Portland, OR 97210, USA. Aim of Investigation: This electrophysiological study was done to test the hypothesis (Roberts, PAIN 24:297, 1986) that wide dynamic range (WDR) neurons in the spinal cord mediate both the spontaneous burning pain and allodynia characteristic of disorders like causalgia and reflex sympathetic dystrophy. Methods: Single unit recordings were made from functionally identified neurons in pentobarbital anesthetized cats. The skin in the receptive field was stimulated mechanically, and the sympathetic trunk was stimulated electrically to evoke afferent activity through sympatheticsensory coupling in the skin. Results: Many WDR neurons were activated by sflpathetic stimulation, buthighhreshold neurons were unresponsive. Sympathetic activation of WDR neurons was blocked by cold or local anesthesia in the receptive field and by intravenous injection of the alpha-adrenergic blocker, Many of the neurons were antidromically activated from phentolamine. ascending fiber tracts. Sympathetic activation was most coimaon (72% of 68 neurons) in WDR neurons which had low mechanical thresholds (cl.2 gm); those with relatively high thresholds (>3.5 gm) were much less responsive Noxious thermal stimulation of to sympathetic stimulation (9% of 11). the receptive field potentiated their responses to sflpathetic stimulation; Sympathetically maintained pain is most likely to be Conclusion: mediated by activity in subsets of sensitized WDR neurons.
THE HETEROSEGMENTALLYACTIVATED SLOW POSITIVE CORD DORSUM POTENTIAL. K. Shimoji, H. Fujioka*, T. Hokari* and T. Takada*, Department of Anesthesiology,Niigata University School of Medicine, Niigata 951, Japan Aim of Investigation: Recently, a large amount of information has been accumulated on brain stem control of spinal cord (SC) functions. The present study was undertaken to test the effects of descending volleys activated by a feedback on spinal function in terms of the SC potentials. Methods: The rats were fixed in a stereotaxic apparatus for the SC under general anesthesia. Bilateral thoracotomy, 10 mm in diameter, was performed to minimize any respiratory movement of the SC. The SC was exposed at the C and Ll-5 vertebral levels. Recording electrodes, T7 Ag-AgCl wires, 168"; in-diameter,were placed through mineral oil onto the dorsal surfaces of the cervical and lumbar enlargements in midline. A glass microelectrode filled with 3 M KC1 was inserted into the lamina V of Lexed at the lumbar dorsal horn where the largest negative wave was recorded in response to hindpaw electrical stimulation. Results: Moderate to intense stimulation of the fore- and hindpaws produced a long-latency heterosegmentallyactivated slow positive wave (HSP) at the lumbar and cervical regions of the cord dorsum, respectively. With level, the HSP disappeared almost completespinal transection at the C 1-ztial component, with simultaneous abolishment ly, leaving a trace of the In of the second component of the P wave. The inhibition of firing of the WDR neurons by electrical stimulation lasted from approximately 20 to 120 ms and showed a similar time course of that of the HSP. Conclusion: Thus, most components of the HSP are considered to be produced by a feed-back loop via the supraspinal structures. The WDR neuronal activities are suggested to be inhibited by the PAD activated through a feedback loop via the supraspinal structures.
WHICH SPINAL NOCICEPTIVE NEURONS ARE CAPABLE OF MEDIATING SYMPATHETICALLY MAINTAINED PAIN? W.J.Roberts & M.E. Foglesong*, Neurological Sciences Institute, Good Samaritan.Hospital and Medical Center, Portland, OR 97210, USA. Aim of Investigation: This electrophysiological study was done to test the hypothesis (Roberts, PAIN 24:297, 1986) that wide dynamic range (WDR) neurons in the spinal cord mediate both the spontaneous burning pain and allodynia characteristic of disorders like causalgia and reflex sympathetic dystrophy. Methods: Single unit recordings were made from functionally identified neurons in pentobarbital anesthetized cats. The skin in the receptive field was stimulated mechanically, and the sympathetic trunk was stimulated electrically to evoke afferent activity through sympatheticsensory coupling in the skin. Results: Many WDR neurons were activated by sflpathetic stimulation, buthighhreshold neurons were unresponsive. Sympathetic activation of WDR neurons was blocked by cold or local anesthesia in the receptive field and by intravenous injection of the alpha-adrenergic blocker, Many of the neurons were antidromically activated from phentolamine. ascending fiber tracts. Sympathetic activation was most coimaon (72% of 68 neurons) in WDR neurons which had low mechanical thresholds (cl.2 gm); those with relatively high thresholds (>3.5 gm) were much less responsive Noxious thermal stimulation of to sympathetic stimulation (9% of 11). the receptive field potentiated their responses to sflpathetic stimulation; Sympathetically maintained pain is most likely to be Conclusion: mediated by activity in subsets of sensitized WDR neurons.
THE HETEROSEGMENTALLYACTIVATED SLOW POSITIVE CORD DORSUM POTENTIAL. K. Shimoji, H. Fujioka*, T. Hokari* and T. Takada*, Department of Anesthesiology,Niigata University School of Medicine, Niigata 951, Japan Aim of Investigation: Recently, a large amount of information has been accumulated on brain stem control of spinal cord (SC) functions. The present study was undertaken to test the effects of descending volleys activated by a feedback on spinal function in terms of the SC potentials. Methods: The rats were fixed in a stereotaxic apparatus for the SC under general anesthesia. Bilateral thoracotomy, 10 mm in diameter, was performed to minimize any respiratory movement of the SC. The SC was exposed at the C and Ll-5 vertebral levels. Recording electrodes, T7 Ag-AgCl wires, 168"; in-diameter,were placed through mineral oil onto the dorsal surfaces of the cervical and lumbar enlargements in midline. A glass microelectrode filled with 3 M KC1 was inserted into the lamina V of Lexed at the lumbar dorsal horn where the largest negative wave was recorded in response to hindpaw electrical stimulation. Results: Moderate to intense stimulation of the fore- and hindpaws produced a long-latency heterosegmentallyactivated slow positive wave (HSP) at the lumbar and cervical regions of the cord dorsum, respectively. With level, the HSP disappeared almost completespinal transection at the C 1-ztial component, with simultaneous abolishment ly, leaving a trace of the In of the second component of the P wave. The inhibition of firing of the WDR neurons by electrical stimulation lasted from approximately 20 to 120 ms and showed a similar time course of that of the HSP. Conclusion: Thus, most components of the HSP are considered to be produced by a feed-back loop via the supraspinal structures. The WDR neuronal activities are suggested to be inhibited by the PAD activated through a feedback loop via the supraspinal structures.