Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0344307 (analgesia)
 28,200 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Discharges of lumbar dorsal horn neurons were evoked by noxious radiant skin heating, and inhibition of the heat-evoked responses by stimulation of the mesencephalic periaqueductal gray was investigated in N2O-anesthetized cats. 2. Thirty-seven units selected on the basis of receiving afferent C-fiber input from the posterior tibial and/or superficial peroneal nerves responded vigorously to 50 degrees C heating of the plantar surface of the ipsilateral hindpaw. All discharges were inhibited by periaqueductal gray stimulation (PAGS) at current strengths of 300--900 microA; the mean threshold for inhibition was 167 microamperemeter. The mean frequency of the inhibited discharge was 39% of the control response. 3. Effective PAGS sites were distributed throughout the ventral PAG bilaterally. Stimulus current-distance estimates indicate that small (0.5--1.2 mm diameter) volumes of tissue within the PAG were stimulated. 4. A monotonic relationship between temperature and unitary discharge was found for skin heating from threshold to about 50 degrees C. PAGS resulted in a decrease in the slope of the curve plotting discharge against temperature, without altering the threshold. 5. Inhibition of the heat-evoked discharges rarely outlasted the PAGS. 6. Possible neural substrates for descending inhibition and correlates with neural mechanisms of analgesia are discussed.
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PMID:Inhibition of spinal neuronal responses to noxious skin heating by stimulation of mesencephalic periaqueductal gray in the cat. 42 77

The effect of morphine on extracellular histamine levels in two regions of the rat midbrain was studied in vivo by microdialysis. Morphine (5.6 and 12.8 mg/kg, s.c.) significantly and dose-dependently increased extracellular histamine levels in the periaqueductal grey, while no significant effect was observed in the reticular formation. In addition, no significant effect of sequential saline injections was observed on extracellular histamine levels in the periaqueductal grey. Since morphine has no effect on histamine catabolism, these results suggest that morphine increases histamine release in the rat PAG, a site where morphine and histamine are known to have analgesic action. Taken with earlier studies showing the ability of H2 antagonists to block morphine analgesia, these results support the hypothesis that histamine and H2 receptors are important in mediating morphine analgesia in the rat periaqueductal grey. The cellular origin of the extracellular histamine, and the mechanism of this morphine effect remain to be determined.
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PMID:Morphine-induced increases of extracellular histamine levels in the periaqueductal grey in vivo: a microdialysis study. 161 9

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

Lesion of the preoptic area (POA) or medial arcuate nucleus (M-HARN) abolished acupuncture analgesia (AA). Potentials in the median eminence (ME) evoked by stimulation of the acupuncture point (AP) were not affected by lesion of either the POA or M-HARN alone, but were abolished by concurrent lesion of both. No analgesia was produced by stimulation of the POA. Analgesia produced by stimulation of the M-HARN was abolished by lesion of the POA, and the abolished analgesia was restored by concurrent stimulation of the POA and M-HARN, hence POA and M-HARN outputs might converge in the ME to produce AA. Similar convergence from the anterior arcuate nucleus (A-HARN) and POA to the ME was observed in analgesia (NAA) produced by stimulation of a nonacupuncture point (NAP). Two pathways diverged from the lateral hypothalamus in the AA afferent pathway and two from the lateral periaqueductal central gray (L-PAG) in the NAA afferent pathway. POA potentials evoked by stimulation of the AP were reversed by naloxone, and those evoked by stimulation of the AP were reversed by dexamethasone. ACTH sensitive sites were found in both the L-PAG and the anterior hypothalamus.
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PMID:Convergence from the preoptic area and arcuate nucleus to the median eminence in acupuncture and nonacupuncture point stimulation analgesia. 193 97

Previous studies have shown that 2 Hz but not 100 Hz electroacupuncture (EA) stimulation released beta-endorphin in PAG of the rat to induce analgesia. The present study was undertaken to see whether dynorphin plays a role in PAG in mediating analgesia induced by low and high frequency EA. Injection of affinity purified dynorphin antibody (1:350,000 in RIA titer) 1 microliter into PAG blocked 2 Hz EA analgesia almost completely, and 15 Hz EA analgesia partly, leaving 100 Hz EA analgesia intact. This blocking effect was totally disappeared when the antibody was diluted to 1/10 of its original concentration (1:35,000). Besides, injection of dynorphin into PAG through chronically implanted cannula showed no analgesic effect. The results suggest that the blockade of 2 Hz EA analgesia by high titer dynorphin antibody injected into PAG may have been the result of cross reactivity of the antibody to other opioid peptides (such as beta-endorphin, enkephalin, etc) released in the PAG area. The data also stress the importance of using antibodies of proper titer and concentration to exclude false positive or false negative conclusions in adopting the antibody microinjection techniques, as was repeatedly shown in the immunohistochemical studies.
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PMID:[Influence of microinjection of dynorphin antibody into periaqueductal gray (PAG) on analgesia induced by electroacupuncture of different frequencies in rats]. 198 Apr 31

Antiserum of methionine-enkephalin (Met-Enk) applied intrathecally abolished acupuncture analgesia (AA) caused by low frequency stimulation of an acupuncture point (tibial muscle, APS) of rats, but antisera of leucine-enkephalin (Leu-Enk) and dynorphin (Dyn) did not. Antiserum of Dyn applied intrathecally abolished analgesia (NAA) produced by stimulation of a nonacupuncture point (NAPS) which was revealed by lesion in the analgesia inhibitory system (AIS), whereas antisera of Met-Enk and Leu-Enk did not. NAA was antagonized by the kappa-receptor antagonist, Mr2266, and analgesia was produced by the kappa-agonist, U50-488H, in the AIS lesioned rats. Potentials in the dorsal periaqueductal central gray (D-PAG) evoked by APS were antagonized by naloxone and antiserum of Met-Enk, and those in the lateral PAG (L-PAG) evoked by NAPS were antagonized by Mr2266 and antiserum of Dyn. After adrenalectomy, AA, potentials in the D-PAG, and analgesia caused by stimulation (SPA) of the D-PAG were abolished 12 hour; and NAA, potentials in the L-PAG, and SPA of the L-PAG were abolished in 24 hour. All were then restored one hour after intravenous application of 1 ml of 5% NaCl solution. AA and NAA which were augmented for several hours before their abolition after adrenalectomy were not antagonized by naloxone nor M 2266, respectively. However naloxone and Mr2266 did antagonize AA and NAA, respectively, one hour after treatment with 1 ml of 5% NaCl solution.
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PMID:Differentiation of acupuncture and nonacupuncture points by difference of associated opioids in the spinal cord in production of analgesia by acupuncture and nonacupuncture point stimulation, and relations between sodium and those opioids. 198 42

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


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