The effects of selective opioid antagonists on somatosensory evoked potentials during relative cerebral ischemia in rats

Gunnarsson, Þorsteinn; Sigurdardottir, Svafa; Hoffmann, Pavel; Skarphedinsson, J. O.

doi:10.1016/0024-3205(94)00769-1

Cited by 2 publications

(1 citation statement)

References 33 publications

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“…Morphine is a -selective ligand that can bind to 3 receptors, though its affinity at the 3 site is tenfold lower than at the site [11]. As the antagonist in this experiment, we used Mr2266, which is rather unselective among the different receptors [33,34], because nor-binaltorphimine, a well-known antagonist, is a highly selective 1 antagonist, but it has a very low affinity for 3 receptor [7,11,33,35]. Furthermore, Mr2266 has some affinity for receptors; however, it is conceivable that the two kinds of morphine effects on respiration demonstrated in the present study is mediated by 3 receptors, because it was confirmed that Mr2266 completely antagonized the effects of morphine also in the presence of ␤-FNA.…”

Section: Discussionmentioning

confidence: 99%

Morphine Inhibits Resting Respiration, but It Attenuates Reflexive Respiratory Suppression in Anesthetized Cat through .KAPPA.-Receptor.

Kozaki

Tadaki²,

Kumazawa³

2000

JJP

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We have observed reflexive respiratory suppression, or "poststimulus suppression," induced by electrical stimulation (ES) of thin-fiber muscular afferents [1][2][3]. This suppression is reversed or greatly reduced by naloxone, suggesting the involvement of endogenous opioids. However, when the respiratory level was augmented by means of either hypercapnia, hypoxia, or naloxone administration, the magnitude of the poststimulus suppression was markedly attenuated without consistently altering the facilitatory response during the period of stimulation [4]. Although prestimulus respiratory activity is an important factor in determining the magnitude of the poststimulus suppression, a preliminary study had shown that morphine attenuated the magnitude of the poststimulus suppression when the prestimulus level of respiration was near the control level. Morphine, a common opioid agonist, is well known to depress ventilation [5]. Opioid receptors have been pharmacologically classified into at least three subtypes (, ␦, and ) on the basis of their Key words: morphine, respiration, reflexive respiratory depression, opioid receptor, Mr2266.Abstract: Noxious stimulation of thin-fiber muscular afferents induces a reflexive respiratory suppression that we call "poststimulus respiratory suppression." In anesthetized, vagotomized, paralyzed, and artificially ventilated cats, morphine depressed the level of resting respiration (inhibitory effect on resting respiration) and attenuated the magnitude of the poststimulus respiratory suppression (excitatory effect on the reflexively modified respiration). These two kinds of morphine effects were antagonized by naloxone, suggesting the participation of opioid receptors.To clarify the opioid receptor subtypes responsible for these effects of morphine, three typeselective opioid antagonists-naltrindole (␦ antagonist), ␤-funaltrexamine ( antagonist), and Mr2266 ( antagonist)-were tested. The morphine-induced depression in the resting respiration was antagonized by pretreatment with the antagonist, not with the or ␦ antagonist. Furthermore, the morphine-induced attenuation in the magnitude of the poststimulus suppression was also blocked by the antagonist, but not by the or ␦ antagonist. In conclusion, (1) morphine inhibits resting respiration, but it attenuates the magnitude of the poststimulus respiratory suppression; (2) both these morphine effects are mediated by opioid receptors. The possibility that the 3 receptor, one of the receptors subtypes, mediates the two kinds of morphine effects has been discussed.

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Section: Discussionmentioning

confidence: 99%

Morphine Inhibits Resting Respiration, but It Attenuates Reflexive Respiratory Suppression in Anesthetized Cat through .KAPPA.-Receptor.

Kozaki

Tadaki²,

Kumazawa³

2000

JJP

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Morphinan Neuroprotection: New Insight into the Therapy of Neurodegeneration

et al. 2004

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Neuro-inflammation plays a pivotal role in numerous neurodegenerative disorders, such as Parkinson's disease (PD). Traditional anti-inflammatory drugs have limited therapeutic use because of their narrow spectrum and severe side effects after long-term use. Morphinans are a class of compounds containing the basic morphine structure. The following review will describe novel neuroprotective effects of several morphinans in multiple inflammatory disease models. The potential therapeutic utility and underlying mechanisms of morphinan neuroprotection are discussed.

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The effects of selective opioid antagonists on somatosensory evoked potentials during relative cerebral ischemia in rats

Cited by 2 publications

References 33 publications

Morphine Inhibits Resting Respiration, but It Attenuates Reflexive Respiratory Suppression in Anesthetized Cat through .KAPPA.-Receptor.

Morphine Inhibits Resting Respiration, but It Attenuates Reflexive Respiratory Suppression in Anesthetized Cat through .KAPPA.-Receptor.

Morphinan Neuroprotection: New Insight into the Therapy of Neurodegeneration

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