Enkephalin degradation in mouse brain studied by a new H.P.L.C. method: Further evidence for the involvement of carboxydipeptidase

Guyon, Anne; Roques, Bernárd P.; Guyon, F.; Foucault, Alain; Perdrisot, Rémy; Swerts, Jean-Paul; Schwartz, Jean‐Charles

doi:10.1016/0024-3205(79)90444-2

Cited by 55 publications

(18 citation statements)

References 15 publications

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“…It has been known for some time that enkephalins and dynorphins are highly susceptible to peptidase degradation (Guyon et al, 1979; Hiranuma et al, 1998). Peptidase inhibitors dramatically increase the potency of enkephalin to induce MOR internalization (Song and Marvizon, 2003b; Chen et al, 2007) and analgesia (Kishioka et al, 1994; Chen et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

Acute inflammation induces segmental, bilateral, supraspinally mediated opioid release in the rat spinal cord, as measured by μ-opioid receptor internalization

Chen

Marvizón

2009

Neuroscience

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The objective of this study was to measure opioid release in the spinal cord during acute and long-term inflammation using μ-opioid receptor (MOR) internalization. In particular, we determined whether opioid release occurs in the segments receiving the noxious signals or in the entire spinal cord, and whether it involves supraspinal signals. Internalization of neurokinin 1 receptors (NK1Rs) was measured to track the intensity of the noxious stimulus. Rats received peptidase inhibitors intrathecally to protect opioids from degradation. Acute inflammation of the hindpaw with formalin induced moderate MOR internalization in the L5 segment bilaterally, whereas NK1R internalization occurred only ipsilaterally. MOR internalization was restricted to the lumbar spinal cord, regardless of whether the peptidase inhibitors were injected in a lumbar or thoracic site. Formalin-induced MOR internalization was substantially reduced by isoflurane anesthesia. It was also markedly reduced by a lidocaine block of the cervical-thoracic spinal cord (which did not affect the evoked NK1R internalization) indicating that spinal opioid release is mediated supraspinally. In the absence of peptidase inhibitors, formalin and hindpaw clamp induced a small amount of MOR internalization, which was significantly higher than in controls. To study spinal opioid release during chronic inflammation, we injected Complete Freund's Adjuvant (CFA) in the hindpaw and peptidase inhibitors intrathecally. Two days later, no MOR or NK1R internalization was detected. Furthermore, CFA inflammation decreased MOR internalization induced by clamping the inflamed hindpaw. These results show that acute inflammation, but not chronic inflammation, induce segmental opioid release in the spinal cord that involves supraspinal signals.

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Section: Discussionmentioning

confidence: 99%

Acute inflammation induces segmental, bilateral, supraspinally mediated opioid release in the rat spinal cord, as measured by μ-opioid receptor internalization

Chen

Marvizón

2009

Neuroscience

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“…Another study (Kishioka et al, 1994) found that peptidase inhibitors substantially increased the analgesia produced by Metenkephalin, dynorphin or electroacupuncture. The high susceptibility of enkephalins (Guyon et al, 1979;Hiranuma et al, 1998b) and dynorphins (Hiranuma et al, 1998a;Numata et al, 1988) to peptidase degradation is well-known, and prompted the development of peptidase inhibitors as analgesics (Noble et al, 1992a;Noble et al, 1992b;Noble et al, 1997).…”

Section: Discussionmentioning

confidence: 99%

“…The intrathecal catheter was used to inject a mixture of peptidase inhibitors (at doses of 100 nmol each) onto the lumbar spinal cord. Peptidase inhibitors were amastatin, captopril and phosphoramidon, which inhibit, respectively, aminopeptidases, dipeptidyl carboxypeptidase and neutral endopeptidase, the three enzymes that cleave opioids in the spinal cord (Guyon et al, 1979;Hiranuma et al, 1998a;Hiranuma et al, 1998b;Numata et al, 1988;Song and Marvizon, 2003a). Noxious stimuli were applied 5 min after the intrathecal injection.…”

Section: Noxious Stimulationmentioning

confidence: 99%

Noxious mechanical stimulation evokes the segmental release of opioid peptides that induce μ-opioid receptor internalization in the presence of peptidase inhibitors

et al. 2008

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The internalization of μ-opioid receptors (MORs) provides an ideal way to locate areas of opioid peptide release. We used this method to study opioid release in the spinal cord evoked by noxious stimuli in anesthetized rats. Previous studies have shown that opioids released in the spinal cord produce MOR internalization only when they are protected from peptidase degradation. Accordingly, rats were implanted with chronic intrathecal catheters that were used to inject a mixture of peptidase inhibitors (amastatin, captopril and phosphoramidon) onto the lumbar spinal cord. Five minutes later, a noxious stimulus was delivered to the paw. Lumbar spinal segments were double-stained with antibodies against MORs and neurokinin 1 receptors (NK1Rs) using immunofluorescence. Mechanical stimulation of the hindpaw consisted of repeated 10 sec clamps with a hemostat for 10 min. In the ipsilateral dorsal horn, the stimulus produced abundant NK1R internalization in segments L3-L6, and a more modest but significant MOR internalization in segments L5 and L6. In the contralateral dorsal horn, NK1R was substantially lower and MOR internalization was negligible. The same mechanical stimulus applied to a forepaw did not produce NK1R or MOR internalization in the lumbar spinal cord. Thermal stimulation consisted of immersing a hindpaw in water at 52 °C for 2 min. It produced substantial NK1R internalization ipsilaterally in segment L6, but no MOR internalization. These results show that mechanical stimulation induces segmental opioid release, i.e., in the dorsal horn receiving the noxious signals and not in other spinal segments.

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“…For instance, using a total homogenate from mouse brain, the tripeptide only represents 2-3% of the metabolites, the remainder consisting of ['HITyr (Malfroy et al, 1978). The amino acid is formed by aminopeptidases present mainly in the soluble fraction of the homogenate, acting either on the intact pentapeptide or on [3H]Tyr-Gly-Gly (Guyon et al, 1979). Thus the evaluation of Tyr-Gly-Gly formation might be biased by either subsequent hydroly-sis of the tripeptide or its contamination by [?H]Tyr present in large excess.…”

Section: Discussionmentioning

confidence: 99%

Enkephalin Dipeptidyl Carboxypeptidase (Enkephalinase) Activity: Selective Radioassay, Properties, and Regional Distribution in Human Brain

Llorens

Malfroy

Gacel³

et al. 1982

Journal of Neurochemistry

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The compound [3H]Tyr1,D-Ala2,Leu-OH5]enkephalin has been synthesised as a potentially selective substrate for enkephalin dipeptidyl carboxypeptidase (enkephalinase) activity in brain. Incubations in the presence of homogenates and particulate fractions from rodent and human brain result in the formation of [3H]Tyr-D-Ala-Gly, which can be conveniently isolated by polystyrene bead column chromatography. The enzyme activity responsible for the hydrolysis of the Gly3-Phe4 amide bond of this substrate displays close resemblance to that hydrolysing the natural enkephalins at the same level. In addition, enkephalinase activity characterised in postmortem human brain is closely similar to that in rodent brain, with regard to optimal pH and apparent affinities of various substrates and inhibitors, including the potent compound thiorphan. Enkephalinase activity is distributed in a highly heterogeneous fashion among regions of human brain, the highest levels being found in globus pallidus and pars reticulata of the substantia nigra. This distribution is poorly correlated with that of opiate receptor binding sites but displays some resemblance to that of reported Met5-enkephalin levels.

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Enkephalin degradation in mouse brain studied by a new H.P.L.C. method: Further evidence for the involvement of carboxydipeptidase

Cited by 55 publications

References 15 publications

Acute inflammation induces segmental, bilateral, supraspinally mediated opioid release in the rat spinal cord, as measured by μ-opioid receptor internalization

Acute inflammation induces segmental, bilateral, supraspinally mediated opioid release in the rat spinal cord, as measured by μ-opioid receptor internalization

Noxious mechanical stimulation evokes the segmental release of opioid peptides that induce μ-opioid receptor internalization in the presence of peptidase inhibitors

Enkephalin Dipeptidyl Carboxypeptidase (Enkephalinase) Activity: Selective Radioassay, Properties, and Regional Distribution in Human Brain

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