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Query: UMLS:C0344307 (analgesia)
 28,200 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The long-acting opiate antagonistic potency of naloxazone (NXZ), beta-chlornaltrexamine (beta-CNA) and beta-funaltrexamine (beta-FNA) was compared using three inbred strains of mice, in which morphine induces either analgesia (DBA/2), locomotion (C57BL/6), or both responses (C3H/He). The antagonists were applied SC 24-120 hr before morphine (10 or 20 mg/kg, IP), followed by the tests after 30 min. The minimal dose which completely antagonized morphine-induced analgesia in DBA and locomotion in C57 mice during 24 hr were: for NXZ 50 and 100 mg/kg, for beta-CNA 0.8 and 6.2 mg/kg, for beta-FNA 1.6 and 12.5 mg/kg, respectively. beta-FNA and beta-CNA more potently blocked morphine-induced analgesia in DBA mice than the activity response in the C57 strain. In contrast, beta-FNA prevented morphine-induced locomotion at a lower dose (6.2 mg/kg) than analgesia (greater than 50 mg/kg) in C3H mice, while beta-CNA was equipotent (1.6 mg/kg). In general, beta-CNA turned out to be the most reactive compound, antagonizing morphine effects in low doses up to 120 hr. beta-FNA selectively antagonized either morphine-induced analgesia or locomotion, depending on the strain used. This suggests that a given morphine response might be caused by a genetically determined multiplicity of opiate receptor types and their mutual interactions.
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PMID:Inhibition of morphine-induced analgesia and locomotor activity in strains of mice: a comparison of long-acting opiate antagonists. 665 26

Individually housed DBA/2 mice showed higher pain thresholds than grouped mice. Stress-induced analgesia was evident in grouped but not in isolated mice. Since also morphine injections did not result in analgesic effects in isolated mice, it is suggested that social isolation results in an increased release of opioids which may produce a decreased sensitivity at the opiate receptor level. The role of endogenous opioids in relation to social isolation is discussed.
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PMID:Social isolation: effects on pain threshold and stress-induced analgesia. 668 78

The effects of two opiate agonists-antagonists, butorphanol (4.0 and 8.0 mg/kg) and buprenorphine (0.1 and 1.0 mg/kg), were assessed on locomotor activity and analgesia in DBA/2 and C57BL/6 mice. Different behavioral effects were evident in these strains, which might be characterized by different reactions to the effects of opiates and by differences in endorphin distributions and opiate receptor populations. In particular, buprenorphine acted as an agonist-antagonist to morphine in both strains while a dissociation of butorphanol effects was evident, depending on the strain considered. The clinical implications of these findings are discussed.
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PMID:Differential effects of opiate agonists-antagonists on morphine-induced hyperexcitability and analgesia in mice. 678 3

A number of studies are reviewed in relation to a pharmacogenetic approach to the effect of opiates. The behavioral effects of morphine and heroin in different species or strains of animals are considered. In particular, a number of behavioral, neurophysiological, and biochemical correlates of the opiates in different inbred strains of mice are cited. Recent studies concerning the effects of opiates on behavior have utilized the C57BL/6J and the DBA/2J strains, which are characterized by different brain levels and turnover of cholinergic and adrenergic mediators. It has been shown that the effects of opiates on running activity and on analgesia are strain-dependent, and a negative correlation is evident between the two measures in the strains considered. Experiments carried out on mice with septal lesions and on normal mice have confirmed that the motor and analgesic effects of morphine in the mouse are two distinct phenomena, which may be explained through different neurophysiological and biochemical models. Differences between the strains considered have also been observed when the ECoG response to morphine administration has been investigated. The results of these experiments have suggested: 1. The existence of a correlation between behavioral activation and sleep-like ECoG patterns. 2. The existence of a similarity between the effects of the anticholinergic drugs and those of morphine, since a dissociation between ECoG and behavior became evident following morphine administration. Some studies have also suggested that the environmental factors play an important role in determining the stimulating effects of morphine. This effect was absent in "experience" mice (i.e., in subjects already tested in the apparatus), as compared with naive "inexperienced" animals.
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PMID:Behavioral effects of opiates: a pharmacogenetic analysis. 701 12

A quantitative trait locus (QTL) was detected and mapped to proximal chromosome 10 near the markers Mpmv5 and D10Mit51 with a strong influence on morphine-induced analgesia in the BXD recombinant inbred (RI) strains and in an F2 cross (B6D2F2) between the BXD progenitor strains, C57BL/6 and DBA/2. A LOD score of 3.9 (p < .00002) was seen for analgesia using the hot plate assay. Naloxone Bmax was also associated with this chromosome region in BXD RI mice. The mu opioid receptor gene (Oprm) has recently been mapped to this same chromosome region. The observation that several morphine-related traits and naloxone Bmax appear to be partly determined by this presumed single locus is consistent with the hypothesis that the mu opioid receptor gene, or one of its modulators, is the basis for the QTL.
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PMID:Localization to chromosome 10 of a locus influencing morphine analgesia in crosses derived from C57BL/6 and DBA/2 strains. 764 15

The analgesic and reinforcing effects of morphine were compared in four strains of mice (C57BL/6, BALB/c, DBA, CBA). The analgesic action of morphine was measured in tail immersion (49 degrees C), hot plate (60 degrees C), and tail clip (four-point scale of nociceptive response) tests. The reinforcing action of morphine was studied in i.v. self-administration and conditioned place preference techniques. The results demonstrate strain differences in the analgesic and reinforcing action of morphine in mice. The relative rank order of the strains varied for the several tests as well as for the morphine effects. The lack of correlation between analgesic and reinforcing action of morphine in inbred strains supports the conclusion that analgesia and reinforcement are separate processes with different genetic control.
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PMID:Strain differences in the analgesic and reinforcing action of morphine in mice. 770 Sep 49

In studying the interactions between handling mice and their subsequent analgesic response to an intrathecally (i.t.) administered mu-opioid agonist, DAMGO, it was found that suspending ICR mice by the tail for 1, 5, or 20 sec, 10 min before the tail-flick test, enhanced DAMGO by 5.3-, 7.4- and 23.6-fold, respectively, compared with mice maintained in a level posture. This enhancement was not accompanied by a change in the rostral flow of [3H]-DAMGO (25 ng, i.t.) to the brain (3.7% in 10 min), in its distribution along the neuraxis or in its systemic absorption. However, i.c.v. administration of beta-endorphin (1-27), an antagonist of epsilon opioid receptors, abolished the enhancement of i.t. DAMGO without affecting its basal analgesic potency. Pretreatment with the delta-opioid antagonist naltrindole (5.6 nmol, i.t.,-30 min) also blocked the enhancement of DAMGO without significantly affecting its basal analgesic potency. Alternatively, this same dose of naltrindole injected i.c.v. failed to block the enhancement of DAMGO in suspended mice. A 20-sec suspension failed to enhance i.t. kappa and delta-agonists, but it did enhance i.t. morphine. In mouse strain comparisons, i.t. DAMGO was more potent in C57BL/6J and DBA/2J mice than in C3H/HeJ and ICR mice, but DAMGO was enhanced by a 20-sec suspension in all strains tested. Thus suspending mice by the tail evoked a reflex enhancement of spinal mu agonist-induced analgesia that probably involved both the supraspinal release of beta-endorphin (an endogenous epsilon agonist) and the subsequent spinal release of an endogenous delta-receptor agonist in the reflex pathway.
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PMID:Endogenous opioids released by suspending mice by the tail selectively enhance spinal mu opioid analgesia. 793 69

1. The influence of dexamethasone on morphine analgesia in three different strains of mice (Swiss, DBA/2J and C57BL/6) was studied by using the tail flick test. 2. I.c.v. as well as i.p. injections of dexamethasone did not modify nociceptive response in all strains. 3. I.c.v. injection of dexamethasone significantly reduced morphine analgesia in Swiss mice whereas no effects were observed in DBA/2J and C57BL/6 mice. 4. In addition, i.p. injection of dexamethasone significantly reduced morphine analgesia in all three strains. 5. These results suggest that the use of different genetic strains may provide an useful approach for studying dexamethasone-morphine analgesia interaction.
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PMID:Dexamethasone influence on morphine-induced analgesia in outbred Swiss and inbred DBA/2J and C57BL/6 mice. 793 66

It is known that predator cues (both mammalian odor or avian vocalization) elicit marked analgesia in rodents. The present experiment used olfactory cues produced by an opportunistic rodent predator snake species (100 cc of sawdust scented by Elaphe quatuorlineata). Upon exposure to snake odor (for 30 s, 20 min, or 40 min), adult mice of both the CD-1 and DBA2 strains were assessed for tail-flick or hot-plate analgesia at different times after exposure (from 0 to 40 or 45 min, respectively). In both strains, snake odor exposure induced significant alteration in the frequencies of sniffing, self-grooming, and digging, while it inhibited habituation of locomotor activity in DBA/2 mice. No analgesia emerged with both tests as a consequence of exposure to snake odor. Results suggest that although endogenous analgesia has been demonstrated by other authors to be elicited in response to cues emanating from common and widely distributed mouse predators (such as carnivores or owls), predators such as reptiles, which under natural conditions exert a limited predatory pressure on the house mouse gene pool, may only induce fear-associated behavioral responses but cannot provide ethologically relevant stimuli triggering mouse analgesia.
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PMID:Snake odor alters behavior, but not pain sensitivity in mice. 814 Jan 55

Anxiety has been implicated in the acute nonopioid analgesic reaction seen in defeated mice. In the present study, behavioural responses to the elevated plus-maze test were examined in male DBA/2 mice immediately following defeat by an experienced aggressive conspecific. Compared to home-cage controls, defeat reduced total arm entries and rearing, although anxiety enhancement was indicated by decreases in percent open-arm entries and percent time spent on the open arms. These effects were accompanied by significant increases in nonexploratory behaviour (movement arrest and grooming) and risk assessment (closed arm returns, protected head dipping, and stretch-attend postures). This anxiogenic effect of social defeat was partially replicated in mice merely exposed to the scent of an aggressive male conspecific. The specificity of present findings to socially relevant stressors was confirmed by the general lack of effect on plus-maze behaviour of prior exposure to a novel cage or to interaction with a nonaggressive male. Present results are not only consistent with the anxiety hypothesis of defeat analgesia but also show that the elevated plus-maze test is sensitive to alterations in anxiety produced by ecologically relevant stimuli. Possible implications for pharmacological studies are discussed.
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PMID:Anxiety enhancement in the murine elevated plus maze by immediate prior exposure to social stressors. 844 2


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