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

The purpose of the present study was to examine in rats the relationship between the age-related decline in an opioid receptor system and the function of the endogenous opioid pain-inhibitory system activated by front-paw shock. Results revealed that the analgesia displayed following front-paw shock declined between 5- to 7-month-old, 15- to 17-month-old, and 22- to 24-month-old age groups. The administration of naloxone significantly attenuated the shock-induced analgesia. Thus, the endogenous opioid pain modulatory system activated by front-paw shock (the nucleus raphe alatus and a descending pathway lying within the dorsolateral funiculus of the spinal cord) declines in function with increasing age. This research also confirms that there is a parallel between the age-related decline in the neurochemical indexes of the opioid receptor system and the function of these receptors in producing analgesia in response to aversive stimulation.
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PMID:Environmentally induced analgesia: an age-related decline in an endogenous opioid system. 298 89

Prenatal stress affects the expression of many opioid-regulated behaviors in adulthood, e.g., aggressive, maternal, regulatory, and sexual. In the present report we examined two forms of analgesia, morphine-induced (opioid receptor-mediated), and stress-induced [cold-water swim (CWS), nonopioid] analgesia in adult prenatally-stressed (P-S) male and female rats to determine whether and to what extent these analgesic responses might be altered. Timed-mated Sprague-Dawley females were exposed to heat and restraint stress (three daily 1/2 hour sessions, 0830, 1230, and 1630 hr) from days 15-22 of gestation. Control animals remained undisturbed throughout pregnancy. Between 120-150 days of age, baseline pain sensitivities were determined using a tail-flick monitor. P-S and Control animals were then exposed to 3.5 min cold-water swims (2 degrees C) and pain thresholds were again determined at 30 min intervals for 120 min. P-S females exhibited significantly lower pain thresholds than Control females at the 30 and 60 min marks, whereas P-S and Control males did not differ. Six to eight days later, analgesia was measured for 180 min following morphine (5.0 mg/kg) administration. P-S females exhibited significantly greater analgesia at each time-point after morphine treatment than Controls. Conversely, P-S males were significantly less analgesic than Control males from 60 to 180 min. These data suggest that prenatal stress alters the status of endogenous opiate systems. Such prenatal stress-induced alterations in opiate function may help account for some of the behavioral effects reported in P-S animals.
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PMID:Prenatal stress alters morphine- and stress-induced analgesia in male and female rats. 317 33

From the evidence reviewed above, there is little doubt that ECS activates endogenous opioids and modifies their receptors. Thus, this form of SIA is accompanied by many other corollaries of opioid-like actions, including catalepsy, similar EEG patterns, common autonomic effects, and increases in opioid receptor binding sites. Investigations have further indicated that the amnestic effects of ECS can also be attenuated by naloxone, and that pituitary-derived opioids may play an important role as a predominant source of opioids that contribute to these opioid-like effects following ECS. It is hoped that these many attempts to correlate SIA with other behavioral and physiological endpoints following ECS will provide a more global perspective on the role of endogenous opioid systems in ECS. From these results, it is suggested that other forms of SIA may also share many of these properties in common with ECS-induced SIA. Nonetheless, ECS and other forms of SIA, such as cold water exposure and restraint, share with ECS a common history of clinical use in the treatment of human depression. It is possible that the common thread linking these experimental observations to endogenous opioid systems may provide new insights into the cause and treatment of mental disorders as well as the perception of pain.
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PMID:Electroconvulsive shock activates endogenous opioid systems: behavioral and biochemical correlates. 352 81

The analgesic effects of meperidine, anileridine, codeine and codeine + acetominophen on surgical and non-surgical pain in 101 patients were assessed using the McGill Pain Questionnaire. The quality of analgesia was determined by analyzing the changes in the pain descriptors chosen 1 hour after medication. Meperidine and anileridine differentially reduced pain qualities rated as "bright-phasic" by a student sample. Codeine and codeine + acetominophen produced similar patterns of analgesia that were homogeneous across "bright-phasic" and "dull-tonic" types of pain. The data suggest the possibility that opioids may differ in the quality of analgesia produced either as dose increases or different opioid receptor types are recruited.
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PMID:Qualitative differences in effects of opioids in man: preliminary evidence for multiple mechanisms of analgesic action. 375 41

The endogenous opioids seem likely to be assigned a significant role in the integrated hormonal and metabolic response to exercise. This article reviews the present evidence on exercise and the endogenous opioids, and examines their involvement in a number of widely disparate physiological processes. In considering the role of individual opioid peptides, it is important to remember that many of the tools and techniques now used are still relatively crude. Most studies have demonstrated that serum concentrations of endogenous opioids, in particular beta-endorphin and beta-lipotrophin, increase in response to both acute exercise and training programmes. Elevated serum beta-endorphin concentrations induced by exercise have been linked to several psychological and physiological changes, including mood state changes and 'exercise-induced euphoria', altered pain perception, menstrual disturbances in female athletes, and the stress responses of numerous hormones (growth hormone, ACTH, prolactin, catecholamines and cortisol). Many reports have described a role for the endorphin response as seen during exercise and have used the opioid receptor antagonist, naloxone, to investigate and verify the degree of involvement of the opioids. However, whether the observed increases in peripheral endorphin concentrations are sufficient to cause immediate mood changes, create menstrual cycle dysfunction or alter pain perception is still not resolved. A relatively new implication for the endorphins and associated changes with exercise is in ventilatory regulation. A number of studies have suggested that endogenous opioids depress ventilation and may, therefore, play a role in ventilatory regulation by carbon dioxide, hypoxia and exercise. It may also be possible that during exercise, the perception of fatigue is modulated by an increase of endogenous opioids.
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PMID:Endorphins and exercise. 609 Dec 17

The multiplicity of opioid peptides (endorphins) present in the mammalian CNS finds a counterpart in the existence of various types of opioid receptors (mu, delta, kappa, epsilon). The various receptor types, which possess distinctive relationships to particular opioid peptides, play a distinctive role in pain modulation. At the cerebral level primarily mu- and probably epsilon-receptors, rather than kappa-receptors appear to be involved, and, at the spinal level, primarily mu- and kappa-receptors. The function of delta-receptors at both levels remains unclear. There is certain evidence that the various opioid receptor types (and corresponding ligands) are of variable significance in the control of pain dependent upon the nature of the nociceptive stimulus (e.g. thermal vs. pressure).
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PMID:[The role of multiple opioid receptors and their ligands in pain modulation]. 609 28

Opioid peptides derived from proenkephalin and prodynorphin are differentially distributed in the spinal cord. Proenkephalin peptides are preferentially located in the sacral portion of the cord while prodynorphin peptides are concentrated in the cervical spinal cord. Mu opioid receptor are highly concentrated in superficial layers of the dorsal horn in all the spinal cord. Delta opioid receptor are more diffusely distributed in the gray matter of the spinal cord. These sites are principally located in cervical and thoracic portions of the spinal cord. Kappa opioid receptors are highly concentrated in the superficial layers of the lumbo-sacral spinal cord. Its density decreased in the upper levels of the spinal cord. It appears that mu opioid receptors are indifferentially activated by thermal, pressure and visceral nociceptive inputs. Delta receptors are more likely to be involved in thermal nociception while kappa opioid binding sites are associated to visceral pain nociceptive inputs.
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PMID:Pain, nociception and spinal opioid receptors. 615 41

To determine whether opioid peptide-receptor pharmacological association found in vitro (e.g., enkephalin-delta, dynorphin-kappa) predict anatomical relationships in situ, immunocytochemical and receptor autoradiographic studies were carried out on adjacent sections from the same brains of formaldehyde-perfused rhesus monkeys. Apparent mu and kappa opioid receptors (labeled, respectively, by [3H] naloxone and [3H]bremazocine under different incubation conditions), but not delta opioid receptors (labeled by [3H]D-Ala2, D-Leu5-enkephalin), survived the fixation procedure, and were found to be colocalized throughout the brain. We have observed complex associations between these binding sites and one, two, or all three opioid peptide systems (i.e., proopiomelanocortin, proenkephalin, and prodynorphin) in different brain regions. These multiple opioid peptide-receptor subtype associations are apparent, for example, in neural systems involved in the processing of pain stimuli, and may be important for mediating different types of analgesia. Since differential processing of proenkephalin and prodynorphin can give rise to opioids of varying receptor selectivities, the colocalization of opioid receptor subtypes may signify that such processing is a key regulatory event in determining which receptor subtype is activated and, thus, the physiological consequences of opioid neurotransmission.
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PMID:Anatomical relationship between opioid peptides and receptors in rhesus monkey brain. 615 4

The scarce or absent analgesic effect exhibited by morphine on pain from migraine attack and the poor inhibition of the spasmogenic effect of 5-HT (tested on the hand dorsal vein, computerized venotest) suggest the hypothesis of an opioid receptor deficiency in headache sufferers. Since endogenous opioids control the nociception, the sense of well being, and the vegetative balance, an opioid receptoral hypofunction could be the background of the headache and central panalgia, where the trinity pain, anhedonia, and dysautonomia are the characteristic features.
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PMID:Opioid receptor impairment--underlying mechanism in "pain diseases"? 628 33

We have previously found rat and toad (Bufo marinus) brain to contain inverse ratios of benzomorphan-preferring (kappa/sigma) and morphine-preferring (mu) opioid receptor types. The aim of the present study was to compare in vivo pharmacologic activity of a benzomorphan, ethylketocyclazocine (EKC) and morphine sulfate (MS) in rat and toad. Footshock intensity thresholds for eliciting locomotion were determined and dose-response curves for EKC and MS analgesia were obtained. Drugs were injected subcutaneously. In rats (high mu, low kappa in brain), both compounds produced analgesia and displayed similar sensitivity to naloxone antagonism. The analgesic effects of EKC and MS may, therefore, be mediated by a common receptor type (mu) in this pain test in rats. In toads (high kappa, low mu in brain), MS produced naloxone-reversible analgesia at doses 20-fold higher than were effective in rats. Toads did not display EKC analgesia at doses below those producing motor impairment. Moreover, 50-fold higher doses were required to produce such impairment in toads. Thirty minutes following subcutaneous injection of 3H-EKC, similar concentrations were found in rat and toad brain. Uptake into brain is probably not a factor in the behavioral resistance of toads to EKC.
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PMID:Analgesic effects of ethylketocyclazocine and morphine in rat and toad. 643 31


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