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

Experiments were performed to evaluate the effects on the levels of aspartate, GABA and glutamate in the periaqueductal central gray matter, hypothalamus, midbrain reticular formation and cortex of mouse brain following various treatments. The results indicate that only glutamate among the 3 neurohumors is systematically altered relative to the experimental manipulations. Moreover, among the 4 brain areas examined, the data implicate only the periaqueductal central gray matter as a locus of morphine's antinociceptive action. Morphine also appears to produce a drug-specific effect in hypothalamus which, however, is not analgesia-related. There were no significant pain, stress or drug-related effects on the levels of glutamate in either the midbrain reticular formation or the cortex.
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PMID:Morphine and pain: effects on aspartate, GABA and glutamate in four discrete areas of mouse brain. 93 43

Experiments were performed to determine 1) whether synergism existed between morphine and gamma-hydroxybutyrate in the production of analgesia and 2) the effect of each of these agents on pain-induced changes in brain amino acid content in mice. The analgetic ED50 for both agents was determined using hot plate and tail-flick procedures. The combination of one-half the ED50 of each agent produced an effect equivalent to the ED50 of either agent administered alone in the hot plate but not in the tail-flick test. Although both agents produced an unresponsiveness to noxious stimulation, only morphine prevented pain-induced alterations in brain GABA and glutamate levels.
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PMID:An evaluation of the analgesia induced by morphine gamma-hydroxybutyrate. 114 17

Pain syndrome induced by daily peritoneal electrostimulation in rats within two weeks caused decrease in body weight and in motor behavior in open-field test. Moreover, there were a decrease in thymus weight, an increase in adrenal weight and an appearance in most of animals of gastric mucosal erosions. The disturbances of the behavior and somatic state of animals are accompanied by changes of GABA and energy metabolism in the neurons of the frontal cortex. These changes manifested themselves in activation of GABA degradation with simultaneous rise of the succinate--but not isocitrate dehydrogenase activity, inhibition of glutamate dehydrogenase activity and worsening of blood supply to neurons. Chronic (14 days) administration of GABA positive drugs (baclofen--7.5-12.5 mg/kg; depakin--200-400 mg/kg) increases resistance of animals to long-term exposure to pain, which correlates with the normalization of GABA and energy metabolism. Moreover, depakin but not baclofen prevents the development of the microcirculatory disturbances, which is indicated by the normalization of either the activity of sodium phosphatase or the quantity of active capillaries. It is suggested that activation of the inhibitory GABA-ergic mechanisms is a factor of both neuromediatory and metabolic adaptation to the pain.
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PMID:[Role of the GABA system in adaptation to long-term pain stimulation]. 130 7

We have recently described extensive inhibitory interactions between inputs to the ventroposterolateral (VPL) (Roberts and Wells 1990, 1991) and ventroposteromedial (VPM) (Salt 1989) portions of the ventrobasal nucleus of the thalamus (VB). We wished to determine whether (i) the inhibition observed in the VPL was operating at the thalamic level, (ii) was dependent on GABA receptors, (iii) was demonstrable on neurons of the ventro-posteromedial nucleus of the thalamus (VPM) and (iv) was operant on test responses evoked by natural stimuli. Conditioning stimulation of sciatic nerve afferents caused inhibition of air jet evoked test responses of single VB neurons in urethane-anaesthetized rats. Both VPM and VPL neurons were subject to inhibition by conditioning stimulation of hindlimb afferents, indicating the wide-spread nature of the inhibitory process. This inhibition was reduced by the iontophoretic application of SR95531, a GABAA receptor antagonist. We conclude that there is a widely distributed inhibitory system operating in the somatic thalamus which involves both the medial and lateral portions of the nucleus and is, at least in part, mediated by GABAA receptors. The possible involvement of inhibitory processes and intrinsic membrane properties of thalamic neurones in the somatotopic plasticity of the sensory thalamus following deafferentation and in deafferentation pain is discussed.
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PMID:Widely distributed GABA-mediated afferent inhibition processes within the ventrobasal thalamus of rat and their possible relevance to pathological pain states and somatotopic plasticity. 132 May 73

Previous evidence has demonstrated that repeated daily administration of the opiate receptor antagonist naloxone prior to assessment of pain sensitivity provokes the development of a nonopioid form of hypoalgesia. The present experiments assessed whether the GABA-benzodiazepine receptor complex may be involved in the mediation of this effect. Male Wistar rats were administered 10 mg/kg naloxone prior to hot-plate tests (48.5 degrees C) for pain sensitivity for 8 consecutive days. Control animals were administered saline prior to, and naloxone 2-4 h after, assessment of pain reactivity. Beginning on the fourth or fifth day of this regimen, animals tested under the influence of naloxone displayed longer paw-lick latencies than controls. Preadministration of the GABAA agonist muscimol (1.0-5.0 mg/kg) and GABAA antagonist bicuculline (0.25-1.0 mg/kg) failed to affect paw-lick latencies in naloxone-tested and control rats. The GABAB receptor agonist baclofen (1.0-5.0 mg/kg) and the benzodiazepine receptor agonist diazepam (1.0-5.0 mg/kg) both elevated paw-lick latencies to the same degree in both groups of animals. These results suggest that the GABA-benzodiazepine receptor complex is not involved in the mediation of naloxone-induced hypoalgesia.
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PMID:Naloxone-induced hypoalgesia: lack of involvement of the GABA-benzodiazepine receptor complex. 133 77

We have evaluated the analgesic effect of continuous intrathecal administration of midazolam in 4 patients using a three-level score (no change, amelioration, and marked improvement). The secondary effects of this drug were also investigated (sedation, nausea, vomiting, respiratory depression, urinary retention, motor dysfunction). In one patient midazolam was the only drug administered, whereas in three patients this drug was associated with morphine. In one patient with a peripheral arteriopathy, midazolam at a dose of 12 mg/day was unable to equal the analgesic effect achieved with 0.4 mg of morphine. The remaining three patients had carcinoma and received a continuous intrathecal perfusion of morphine at increasing daily doses up to 12; 4,8; and 6 mg/day, respectively without pain relief. In these patients the association of midazolam at respective doses of 9; 4-8; and 6 mg/day induced amelioration in one patient and marked improvement in the two other patients. Midazolam did not change the heart rate, respiratory rate, arterial blood pressure, nor body temperature. We believe that the analgesic effect of intrathecal administration of midazolam is due to its coupling with the ionophore complex GABA-spinal benzodiazepine that in turn produces an increment of the GABA amino butyric acid at this level.
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PMID:[Intrathecal administration of morphine, midazolam, and their combination in 4 patients with chronic pain]. 159 51

Local microinjection of GABAA receptor agonists and antagonists was used to characterize the role of GABA-mediated inhibitory processes in the nociceptive modulatory functions of the rostral ventromedial medulla (RVM) in the lightly anesthetized rat. Microinjection of selective GABAA receptor antagonists bicuculline methiodide and SR95531 produced a significant increase in tail-flick (TF) latency. This antinociception was dose related, showed recovery and was attenuated by prior injection of the GABAA receptor agonist THIP at the same site. Microinjection of saline or the glycine receptor antagonist strychnine did not significantly affect TF latency. In contrast, administration of GABAA receptor agonists THIP and muscimol resulted in a significant decrease in TF latency. Microinjections at sites surrounding the RVM did not significantly affect TF latency. These results demonstrate that a GABA-mediated process within the RVM is crucial in permitting execution of the TF and, presumably, other spinal nociceptive reflexes.
Pain 1991 Oct
PMID:GABA-mediated inhibition in rostral ventromedial medulla: role in nociceptive modulation in the lightly anesthetized rat. 166 24

The high density of GABA-benzodiazepine receptors in the superficial dorsal horn suggests a possible involvement of benzodiazepines (BZs) in the modulation of spinal pain processes. In this electrophysiological study we have examined the effects of midazolam (MZ), a water-soluble short-acting BZ, on the activities of 57 nociceptive non-specific dorsal horn cells, one in each animal. Recordings were performed at lumbar level in unanesthetized decerebrate spinal rats before and following intravenous injection of MZ (1, 2 or 5 mg/kg). The spontaneous activity was weakly and significantly but not dose dependently reduced by MZ. For the total neuronal population MZ induced no significant effect on C-fiber evoked responses, whatever the dose used. More precise analysis shows that for 45/55 neurons the responses were slightly depressed, but this effect was not dose dependent. In contrast, A delta-fiber evoked responses were markedly and dose dependently depressed. These effects of MZ were reversed by intravenous administration of the antagonist flumazenil (FZ). Despite the fact that MZ displays a very weak effect on responses due to C-fiber stimulation, the possible involvement of BZs in the modulation of nociceptive transmission at the level of the dorsal horn is discussed on the basis of clinical and experimental findings, taking into account the role of GABAergic mechanisms in sensory events.
Pain 1992 Jan
PMID:Benzodiazepines and pain: effects of midazolam on the activities of nociceptive non-specific dorsal horn neurons in the rat spinal cord. 133 93

A double-blind pilot study was undertaken to test the administration of low doses of the long-acting benzodiazepine drug clonazepam in the management of chronic intractable temporomandibular disorder/myofascial pain patients who were not responsive to occlusal splint, behavioral, and physical therapy. Clonazepam was selected for its long duration and its cholinergic/GABA-ergic/serotonergic, anxiolytic, muscle relaxant, and sedative properties. Clonazepam appears to be effective when compared to a placebo. However, caution must be observed with long-term administration of clonazepam because of potential side effects such as depression and liver dysfunction. Indiscriminate administration of clonazepam may be harmful to the patient.
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PMID:Administration of clonazepam in the treatment of TMD and associated myofascial pain: a double-blind pilot study. 181 46

The present study examined patterns of analgesia by intracerebroventricular (i.c.v.) or intrathecal (i.t.) administration of the serotonin 5-HT3 receptor agonist, 2-methylserotonin (1-100 micrograms) against acute thermal, mechanical or formalin-induced chemo-inflammatory pain in male rats. Neither i.c.v. or i.t. 2-methylserotonin produced motoric, sedative or respiratory effects. I.c.v. 2-methylserotonin was not analgesic at any dose in the pain assays employed. I.t. 2-methylserotonin produced dose-related analgesia in the formalin test with significant effects at 20-100 micrograms doses. In contrast, only the 100 micrograms dose of 2-methylserotonin produced analgesia against thermal pain, and analgesia was not observed at any dose in the mechanical pain test. The effects of 2-methylserotonin (100 micrograms) in the formalin test were attenuated by pretreatment (10 micrograms i.t.) with the 5-HT3 receptor antagonist MDL-72222, opioid antagonist naloxone or GABA antagonist bicuculline; the 5-HT2-receptor antagonist ketanserin or 5-HT1 receptor antagonist mianserin did not affect 2-methylserotonin-induced analgesia. In the thermal test, i.t. pretreatment with MDL-72222, ketanserin, naloxone or bicuculline, but not mianserin, reduced analgesic effects of 2-methylserotonin (100 micrograms i.t.). These findings suggest that spinal 5-HT3, opioid and GABA receptor systems interact to mediate acute chemo-inflammatory pain, and implicate the interaction of these systems with 5-HT2 receptor substrates in analgesia against acute thermal nociception.
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PMID:Analgesic profile of centrally administered 2-methylserotonin against acute pain in rats. 195 80


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