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Query: UMLS:C0030193 (pain)
 261,466 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Guidelines are presented for the neurosurgical treatment of chronic pain. In these guidelines a distinction is made between the pain of cancer and neurogenic pain. In cancer pain the survival time and the location of the lesion are the important guidelines. Possible procedures are: opioids via CSF route, lesions in nociceptive pathways and PV-PAG stimulation of the thalamus. In neurogenic pain, neurostimulation procedures, tailored to the location of the pain are procedures of first choice. There are however specific indications for other procedures depending on the aetiology of the pain. Causalgia and reflex sympathetic dystrophy: sympathetic blockade; Tic douloureux: radio-frequency lesion, glycerol, balloon inflation of the ganglion of Gasser, and microvascular decompression; Plexus avulsion: dorsal root entry zone lesion (D.R.E.Z.). There is a need for controlled prospective neurosurgical trials in which as a minimal rule an independent party should evaluate the results of the surgical procedure.
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PMID:Indications for neurosurgical treatment of chronic pain. 150 53

Analgesia caused by intraperitoneal 0.5 mg/kg morphine (MA) in rats is equivalent to acupuncture analgesia (AA) caused by low frequency stimulation of the tibial muscle (Tsusanli acupuncture point). Analgesia equivalent to both AA and MA was produced by intrathecal application of 0.05 microgram morphine. This analgesia exhibits individual variation in effectiveness which is parallel to those of both AA and MA, and disappears after 250 mg/kg intraperitoneal D-phenylalanine. Analgesia that persisted after termination of acupuncture stimulation was not affected, maximally developed MA and AA were both partially antagonized, and the initial development of AA and MA were completely antagonized by intrathecal application of 0.2 microgram naloxone. Analgesia caused by intrathecal 0.05 microgram morphine was abolished by bilateral lesion of the anterolateral tract (ALT) of the spinal cord and that caused by acupuncture stimulation was abolished by contra-lateral lesion. Analgesia caused by larger doses (0.1-0.2 microgram) of intrathecal morphine was not abolished, but persisted after ALT lesion, unilateral lesion of the dorsal periaqueductal central gray (D-PAG), or hypophysectomy. Potentials were evoked by acupuncture stimulation in the bilateral D-PAG. Analgesia produced by D-PAG stimulation was not affected by ALT lesion nor by intrathecal naloxone, but was abolished by lesion of the dorsolateral funiculus. These results imply two types of morphine action in the spinal cord to produce analgesia: activation of the ascending AA pathway; and direct inhibition of pain message in the spinal cord. They also show that the AA producing pathway ascends contralaterally in the ALT and then bilaterally in the D-PAG.
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PMID:Morphine analgesia mediated by activation of the acupuncture-analgesia-producing system. 167 31

The purpose of this study is to observe the effect of intracerebroventricular (icv) and intra-PAG injection of substance P (SP) on serotonin (5-HT) contents of hypothalamus, hippocampus, striatum and its relation with the change of pain threshold, electroacupuncture (EA) analgesia. The results were as follows: (1) After icv injection of SP, the pain threshold and the 5-HT contents of hypothalamus, hippocampus were significantly increased. After depletion of the 5-HT contents in brain by pCPA, the inhibitor of 5-HT synthesis, the effect of SP on elevating pain threshold and the 5-HT contents of hypothalamus, hippocampus were markedly attenuated, bud did not prevent the analgesic effect of SP (2) The pain threshold and the 5-HT contents of hypothalamus, hippocampus were dose-dependently increased by intra-PAG injection of SP. (3) The intra-PAG injection of SP introduced simultaneously with high or low frequency EA did not affect the change of 5-HT contents of three brain regions, but caused a more marked elevation of pain threshold. These results suggest that the serotoninergic system may be activated by PAG for the mediation of SP induced analgesia. There is a synergic action of analgesia between the effects produced by intra-PAG injection of SP and those by high or low frequency EA.
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PMID:[Effect of intracerebral injection of substance P on serotonin contents of several brain regions and its relation with pain threshold, electroacupuncture analgesia in rats]. 171 75

In current clinical practice, two brain structures are stimulated for the relief of chronic pain, namely the somatosensory thalamic nuclei (VPL-VPM) and the periventricular and periaqueductal gray matter (PVG-PAG). Whereas stimulation of the VPL-VPM is almost exclusively used for the treatment of deafferentation pain, stimulation of the PVG-PAG is mostly used in cases of nociceptive pain. We present our results of VPL-VPM stimulation in 36 patients with deafferentation pain. Initial pain relief was obtained in 61% of patients. To-day, after a mean follow-up of more than 4 years, 30% are still pain free. This success rate was found to be lower than the mean reported success rate of 57%, based on a survey of the world literature. Upon reviewing the literature, it was apparent that the reported success rates vary considerably between different authors. Some tentative explanations are given for this large discrepancy in success rate. The mechanisms by which electrical stimulation of the VPL-VPM suppresses deafferentation pain remain to be elucidated. Recent clinical and experimental findings suggest that a dopaminergic mechanism might be involved.
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PMID:Deep brain stimulation in the treatment of chronic pain in man: where and why? 209 2

12 Wistar rats (220-250g) were divided into control and experimental groups. Pain threshold was determined by WQ-9E Pain Threshold Measuring Apparatus. EA was applied at bilateral "Zusanli" points. The animals showing EA analgesia and the control animals were sacrificed and the ventrolateral part of PAG and the NRM were taken out for electron microscopic observation. The peripheral region of ventrolateral PAG (PAG-PR) and the NRM contained a wide variety of cell types and synaptic relationships. The neurons and axo-dendritic synapses of the PAG-PR and NRM were analysed in EA and control groups. In EA analgesia group, the clear round vesicle-containing presynaptic boutons and the presynaptic bouton with clear round vesicles and granular vesicles showed a significant decrease of their vesicle content. Part of the mitochondria and endoplasmic reticulum in the neurons appeared the expanded profiles. These ultrastructural changes of the PAG and the NRM during EA analgesia may indicate an increased release of acetylcholine, biogenic amines and/or peptide neurotransmitters and that the neurons were in active functional state.
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PMID:[Electron microscopic observation on the effect of electroacupuncture (EA) on the ultrastructure of periaqueductal gray (PAG) and nucleus raphe magnus (NRM) in rats]. 212 75

Electrical stimulation in the PAG has been shown to elicit profound analgesia in experimental animals that is at least in part due to the release of endogenous opioid substances. Electrical stimulation in the thalamic nuclei VPL and VPM inhibits the activation of spinal dorsal horn neurons by noxious stimuli. Acute electrical stimulation in these two targets relieves chronic pain in about 80% of patients. Chronic electrical stimulation by permanently implanted electrodes relieves pain in about 70% of patients with pain of peripheral or nociceptive origin but in only about 50% of patients with central pain resulting from deafferentation. Stimulating electrodes are implanted stereotactically by a burr hole under local anesthesia. Transient complications occur in 15% to 25% of patients and include infections, malfunctions of the stimulating hardware, pain at the implant sites, and mild temporary neurologic deficits. Permanent complications, including hemiparesis, intracranial hemorrhage, and death, occur in 1% to 2% of patients. Brain stimulation is recommended for the treatment of chronic pain in patients in whom other forms of treatment have failed. The technique is reasonably safe and provides pain relief for a group of patients who have exhausted all other therapeutic modalities. Unfortunately, not all patients receive effective pain relief with brain stimulation. Other stimulation targets such as the K-F nucleus in the parabrachial region of the brain stem are currently being explored in an attempt to provide pain relief to a greater proportion of patients. In addition, improvements in stimulation hardware have made the technique easier and more effective.
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PMID:Brain stimulation. 213 74

In some parts of the world, acupuncture has been employed as a method of obtaining analgesia for thousands of years without the mechanism of its action being understood. During the past two decades, evidence has accumulated indicating that acupuncture activates an intrinsic neural network which monitors and modifies the activity of pain-transmitting neurons. The in-suppressing action is partly mediated by endogenous opioid peptides and monoamines. The system is organized at three levels of the neuroaxis: spinal cord, medulla and the midbrain. The raphe magnus nucleus and the spinal cord constitute a fundamental circuit while the PAG funnels the influences from the more rostral structures and collects information from the spinal cord. PAG initiates descending and ascending nihibition resulting in the reduction of pain. The endogenous pain-control system may be elicited by other physiological stimuli and the effect of acupuncture is scarely specific.
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PMID:[Acupuncture analgesia. Neurochemical and neurophysiologic aspects]. 226 67

We have reported that intracerebroventricular (i. c. v.) injection of 1-4 ng of CCK-8 to the rat produced a remarkable antagonistic effect on morphine analgesia. In order to study the species specificity and the site of action, CCK-8 was microinjected into the PAG of the rabbit, and its influence on morphine analgesia and electroacupuncture analgesia was observed. The latency of the escape response (ERL) to radiant heat focused on the snout was measured as an index of the pain threshold. Microinjections were made via cannulae chronically implanted into the PAG. The drug solutions were delivered in a volume of 1 microliter, at a speed of 0.125 microliter/min. The ERL was measured for a period of 60 or 70 minutes at 10 min intervals. 1. CCK-8 administered unilaterally to the PAG of the rabbit at a dose of 3 ng antagonized the analgesia induced by morphine (4 mg/kg, i. v.) by 73% (P less than 0.001), and reduced the analgesic effect of electroacupuncture by 67% (P less than 0.001). These effects were dose-dependent within the range from 1.5 ng to 6.0 ng. The effect of CCK-8 was reversed by CCK receptor blocker proglumide (4 microliters, intra-PAG injection). Unsulfated CCK-8 (CCK-us) had no effect in this regard. These results indicate that in the PAG of the rabbit, exogenously administered CCK-8 was capable of antagonizing opioid analgesia by the activation of CCK receptors. 2. Two groups of rabbits were given with morphine (2 mg/kg, i. v.) and simultaneous injection of CCK-8 antiserum (CCK-AS, 1 microliter) or normal rabbit serum (NRS) into the PAG.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Antagonism of morphine analgesia and electroacupuncture analgesia by cholecystokinin octapeptide (CCK-8) administered in periaqueductal gray (PAG) of the rabbits]. 260 48

With electric stimulation of the splanchnic nerve or the skin of the tip of rabbit's ear to measure visceral or somatic pain threshold, we studied the effects of noradrenaline microinjection into the septal nucleus on visceral pain and somatic pain and the relationship between the intraseptal noradrenaline and the intra-PAG opiate peptidergic system. There was no effect on visceral pain threshold after injections of alpha-agonist clonidine (10 micrograms/2 microliters) or alpha-antagonist phentolamine (10 micrograms/2 microliters). In a group injected with beta-agonist isoprenaline (1 micrograms/2 microliters), visceral pain threshold was raised remarkably, while beta-antagonist propranolol (10 micrograms/2 microliters) injected into bilateral septal nuclei decreased visceral pain threshold. Phentolamine (10 micrograms/2 microliters) or propranolol (10 micrograms/2 microliters) injected into septal nucleus induced an elevation of somatic pain threshold. The results indicate that the beta-receptor in spetal nucleus plays an important role in the modulation of visceral pain. Both alpha-and beta- adrenergic receptors have effects on the modulation of somatic pain. Intra-PAG microinjection of naloxone (1 micrograms/1 microliters) attenuated visceral analgesia produced by injection of isoprenaline (1 micrograms/2 microliters) into septal nucleus. Microinjection of anti-leu-enkephalin antiserum (1:20,000) into PAG also attenuated the analgesia. When microinjection of isoprenaline into septal nucleus produced analgesia, the release of leu-enkephalin immunoreactive-like-substance in PAG was significantly increased. The results suggest that the analgesic effect of intra-septal noradrenaline on visceral pain is somehow related with the endogenous opiate peptidergic system in PAG, and the leu-enkephalin in PAG plays an important role in this process.
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PMID:[Effect of intraseptal noradrenaline on somatic and visceral pain threshold of rabbits]. 276 39

The descending inhibitory effects of electrical midbrain stimulation on identified lumbar spinothalamic tract (STT) neurons were investigated in rats anesthetized with sodium pentobarbital. STT units were identified by their antidromic response to stimulation in the contralateral ventrobasal thalamus or medial lemniscus (mean conduction velocity: 18-20 m/sec). Thirty-two of 43 dorsal horn multireceptive STT units gave reproducible responses to noxious heat stimuli (42-56 degrees C, 10 sec) applied to the ventral hind paw. All STT units' responses were suppressed during stimulation (100 msec trains at 100 Hz, 3/sec, 15-300 microA) in PAG or LRF bilaterally. On- and offset of inhibition was rapid (less than 1 sec). STT unit responses to noxious heat were more effectively suppressed by LRF than PAG stimulation, based on statistically significant differences in mean thresholds for inhibition, slopes of current-inhibition plots, and mean current intensities evoking 50% inhibition. Mapping experiments revealed lowest-threshold (less than 25 microA) sites for inhibition to be in ventral PAG, subjacent tegmentum, and LRF bilaterally. STT unit responses increased with graded increases in stimulus temperature from threshold (mean: 46 degrees C) to 56 degrees C. Slopes of temperature-response functions were significantly reduced with little change in threshold during PAG stimulation, whereas these functions were shifted in a parallel manner toward higher temperatures during LRF stimulation. The serotonin antagonist methysergide reduced or blocked PAG- or LRF-evoked inhibition in 3/5 and 5/12 STT units, respectively. These results indicate that STT units are subject to different inhibitory controls from PAG and LRF.
Pain 1988 May
PMID:Inhibition of rat spinothalamic tract neuronal responses to noxious skin heating by stimulation in midbrain periaqueductal gray or lateral reticular formation. 338 May 61


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