The Effects of GABA-receptor Antagonists on the Spinal Cord Stimulation-induced Antinociception in Cats / 대한마취과학회지

BACKGROUND: Spinal cord stimulation (SCS) is a clinical off spring of the gate-control theory and known as an effective treatment for pain from a neurogenic origin. The prolonged pain relief following a short stimulation period is believed to be related with the GABAergic system. The aims of this study were to see if the SCS, similar to that being used in clinical condition, suppressed the nociceptive transmission in the spinal dorsal horn, and if so, which type of GABA receptor may be involved in the antinociceptive process. METHODS: The cord dorsum potential (CDP) was recorded at the dorsal root entry zone of the lumbosacral enlargement for a long time period (60 min) in response to electrical stimulation of the dorsal root, respectively, after SCS in anesthetized cats. CDP was recorded after intrathecal application of bicuculline (GABA (A) receptor antagonist) and phaclofen (GABA (B) receptor antagonist) and 20 min after SCS that followed the intrathecal application of bicuculline or phaclofen. Asigma- and C-fiber wave responses were differentiated according to the conduction velocity. RESULTS: The C-fiber wave decreased significantly after SCS but the Asigma-fiber wave did not on the CDP. After intrathecal administration of bicuculline, the Asigma- and C-fiber waves increased significantly and bicuculline also prevented a SCS-induced reduction of the C-fiber wave. Phaclofen did not change the amplitude of Asigma- and C-fiber wave. When the phaclofen was administered intrathecally, SCS did not decrease the amplitude of the Asigma- and C-fiber waves. CONCLUSIONS: In conclusion, the present results indicate that SCS suppresses C-fiber transmission of acute nociceptive electrical stimuli and both GABA (A) and (B) receptors mediate the long-lasting antinociceptive effect of SCS.

The Effects of Spinal Cord Stimulation on the Spinal Nociceptive Process Evaluated by Cord Dorsum Potential in Cats / 대한마취과학회지

BACKGROUND: The pain-inhibitory effects of spinal cord stimulation (SCS) may be exerted at two alternative or complementary levels, segmentally or supraspinally. However the actual pathways, site of action, and synaptic relays are poorly understood. No data is available which concerns the changes in cord dorsum potential (CDP) associated with a single neuronal level, after SCS. METHODS: SCS was performed in normal and spinalized cats. At the lumbosacral enlargement, CDP and extracellular single cell activity in response to electrical stimulation of Asigma- or C-fiber of the dorsal root or sciatic nerve were recorded. RESULTS: The resulting CDP consisted of characteristic waves of Asigma- and C-fiber with a different time latency. CDP sno significant differences in the amplitude of Asigma- and C-fiber wave between the normal and spinalized cats. In both groups, CDP showed decrease in the amplitude of C-fiber wave. Single cell responses were either increased or decreased after SCS. The C- response changed more marKedly than the A-response in both the normal and spinalized cats. In the bicuculline administered cats, single cell responses increased after SCS, but no change was found in the amplitude of CDP. CONCLUSIONS: The above results might indicate that SCS suppresses C-fiber transmission of nociceptive electrical stimuli via a segmental inhibitory mechanism, and that SCS is more effective in blocKing the transmission of nociceptive electrical stimuli via the C-fiber than Asigma-fiber.

The Changes in Cord Dorsum Potential after Spinal Cord Stimulation / 대한마취과학회지

BACKGROUND: Spinal cord stimulation(SCS) evolved as a direct clinical application of the famous gate-control theory, the idea of activating the central collaterals of large afferent fibers contained in the dorsal column. It is well known that the cord dorsum potential(CDP) evoked by stimulation of dorsal roots or peripheral nerves can be recorded from the cord surface in spinal animals. However, there have been no data about the changes in CDP after SCS. METHODS: Using ball-type electrode, CDP was recorded at the dorsal root entry zone of lumbosacral enlargement in anesthetized cats. The dorsal root was stimulated electrically to activate Adelta-fiber(single pulse of 0.2 ms duration and 1 mA intensity) and C-fiber(single pulse of 0.2 ms duration and 10 mA intensity). Potentials were averaged 10 times and measured before(control) and immediately after, and 10, 20, 30, 40, 50, 60 min after SCS for 20 min. RESULTS: CDP elicited by dorsal root stimulation consisted of the characteristic waves of Adelta-fiber and C-fiber with different time latency. CDP showed significant decrease in the amplitude of C-fiber wave immediately after SCS(75.0+/-8.8%), and 20 min(69.0+/-7.9%), 30 min(75.1+/-4.4%), 40 min(75.4+/-4.4%), 50 min(78.3+/-5.9%), but not 10 min and 60 min, after SCS. However there were no statistically significant decrease in the amplitude of Adelta-fiber wave after SCS. CONCLUSIONS: The above results indicates that SCS suppresses the transmission of nociceptive electrical stimuli via C-fiber, while SCS has little influence on the transmission of electrical nociceptive stimuli via Adelta-fiber.

THE INHIBITORY EFFECT OF STIMULATION IN PERIAQUEDUCTAL GREY ON NEURONS IN SPINAL DORSAL HORN AND ITS RELATION TO PAG-CDP / 西安交通大学学报(医学版)

The cord dorsum potential evoked by stimulation in the ventrolateral aspect of periaqueductal grey (PAG-CDP) was recorded from the dorsal surface of the spinal lumbosacral cord in rats. PAG stimulation with the same parameters as for producing PAG-CDP inhibited the C discharges of convergent neurons in spinal dorsal horn. There was a positive correlation between the time course of the inhibitory effect of PAG on convergent neurons and the duration of the slow wave of PAG-CDP. a positive correlation also presented between the latencies of the PAG inhibition and the slow wave. Furthermore, the PAG inhibition did not appear when the intensity of PAG stimulation was below the threshold of PAG-CDP. These results indicate that the presynaptic inhibition is involved in the PAG inhibition of the C discharges of convergent neurons in spinal dorsal horn.