Biomedical subjects

L F Tseng

Publications and source records attributed to L F Tseng.

At least 55 records · Page 3Linked to original sources

PubMed1998

Characterization of endomorphin-1 and -2 on [35S]GTPgammaS binding in the mouse spinal cord.

In the present study, G-protein activation by newly-isolated opioid peptides, endomorphin-1 and -2, was examined in the mouse spinal cord by monitoring the binding of the non-hydrolyzable analog of GTP, guanosine-5'-O-(3-[35S]thio)triphosphate ([35S]GTPgammaS). Both endomorphin-1 and -2 increased [35S]GTPgammaS binding to mouse spinal cord membranes in a concentration-dependent and saturable manner and reached a maximal stimulation of 57.3+/-5.0 and 60.2+/-3.2%, respectively, at 10 microM. In contrast, the synthetic selective micro-opioid receptor agonist [D-Ala2,NHPhe4,Gly-ol]enkephalin (DAMGO) had a much greater efficacy and produced 103.4+/-5.4% of the maximal stimulation. The receptor specificity of endomorphin-stimulated [35S]GTPgammaS binding was verified by co-incubating membranes with endomorphins in the presence of specific micro-(beta-funaltrexamine and D-Phe-Cys-D-Tyr-Om-Thr-Pen-Thr-NH2 (CTOP)), delta-(naltrindole) or K-(nor-binaltorphimine) opioid receptor antagonists. Co-incubation with either beta-funaltrexamine or CTOP blocked both endomorphin-1- and-2-stimulated [35S]GTPgammaS binding in a concentration-dependent manner, whereas neither naltrindole nor nor-binaltorphimine had any effect on the [35S]GTPgammaS binding stimulated by either endomorphin-1 or -2. The data presented indicate that either endomorphin-1 or -2 activate G-proteins by specific stimulation of micro-opioid receptors, and may act as partial agonists with moderate catalytic efficacies in the mouse spinal cord.

Animals↗

PubMed1998

Evidence for the existence of the beta-endorphin-sensitive "epsilon-opioid receptor" in the brain: the mechanisms of epsilon-mediated antinociception.

Recently, mu-, delta- and kappa-opioid receptors have been cloned and relatively well-characterized. In addition to three major opioid receptor types, more extensive studies have suggested the possible existence of other opioid receptor types that can be classified as non-mu, non-delta and non-kappa. Based upon anatomical and binding studies in the brain, the sensitive site for an endogenous opioid peptide, beta-endorphin, has been postulated to account for the unique characteristics of the opioid receptor defined as a putative epsilon-opioid receptor. Many epsilon-opioid receptors are functionally coupled to G-proteins. The functional epsilon-opioid receptors in the brain are stimulated by bremazocine and etorphine as well as beta-endorphin, but not by selective mu-, delta- or kappa-opioid receptor agonists. Epsilon-opioid receptor agonists injected into the brain produce profound antinociception. The brain sites most sensitive to epsilon-agonist-induced antinociception are located in the caudal medial medulla such as the nucleus raphe obscures, nucleus raphe pallidus and the adjacent midline reticular formation. The stimulation of epsilon-opioid receptors in the brain facilitates the descending enkephalinergic pathway, which probably originates from the brainstem terminating at the spinal cord. The endogenous opioid Met-enkephalin, released in the spinal cord by activation of supraspinal epsilon-opioid receptors, stimulates spinal delta2-opioid receptors for the production of antinociception. It is noteworthy that the epsilon-opioid receptor-mediated pain control system is different from that of other opioid systems. Although there appears to be no epsilon-selective ligand currently available, these findings provide strong evidence for the existence of the putative epsilon-opioid receptor and its unique function in the brain.

Amino Acid Sequence↗

PubMed1997

Supraspinal delta 1-opioid receptor-mediated antinociceptive properties of (-)-TAN-67 in diabetic mice.

The antinociceptive potencies of the enantiomorphs of TAN-67 (2-methyl-4-alpha alpha-(3-hydroxyphenyl)-1,2,3,4,4 a 5, 12, 12 a alpha-octahydroquinolino[2,3,3,-g]isoquinoline), (-)-TAN-67 and (+)-TAN-67, given intracerebroventricularly (i.c.v.) on the antinociceptive response were studied in streptozotocin-induced diabetic mice using the tail-flick test. (-)-TAN-67 at doses of 3-10 micrograms given i.c.v. produced dose-dependent inhibition of the tail-flick response in both non-diabetic and diabetic mice. The antinociceptive effect of (-)-TAN-67 in the tail-flick test in diabetic mice was greater than that in non-diabetic mice. The antinociceptive effect of (-)-TAN-67 was not antagonized by pretreatment with either beta-funaltrexamine, a selective mu-opioid receptor antagonist, or nor-binaltorphimine, a selective kappa-opioid receptor antagonist. When 7-benzylidenenaltrexone, a selective delta 1-opioid receptor antagonist, was administered 10 min before treatment with (-)-TAN-67, the antinociceptive effect of (-)-TAN-67 was significantly antagonized. However, naltriben, a selective delta 2-opioid receptor antagonist, had no significant effect on the antinociceptive effect of (-)-TAN-67. On the other hand, in the tail-flick test. (+)-TAN-67 at doses of 3-30 micrograms given i.c.v. did not produce dose-dependent inhibition of the tail-flick response in either non-diabetic or diabetic mice. In conclusion, (-)-TAN-67, but not its enantiomer (+)-TAN-67, produced an antinociceptive effect through the activation of delta 1-opioid receptors.

Analgesics↗

PubMed1997

Use of antisense oligodeoxynucleotide to delta-opioid receptor mRNA in the study of turnover of delta-opioid receptors in the spinal cord of the mouse.

Pretreatment of male ICR mice with an antisense oligodeoxynucleotide to delta-opioid receptor mRNA (DOR AS oligo, 163 pmol) given intrathecally (i.t.) once a day for 1-3 days produced a time-dependent attenuation of antinociception produced by i.t.-challenged [D-Ala2] deltorphin II (6.4 nmol), a delta-opioid receptor agonist. The attenuation of the [D-Ala2]deltorphin II-induced antinociception caused by pretreatment with DOR AS oligo given i.t. daily was blocked by co-pretreatment with naltriben (14.5 nmol), a delta-opioid receptor antagonist, but was markedly enhanced by concomitant pretreatment with thiorphan (19.7 nmol) or bestatin (14.5 nmol), which inhibits the degradation of endogenously released Met-enkephalin. Concomitant pretreatment with antiserum to Met-enkephalin, but not with antiserum to Leu-enkephalin, beta-endorphin or dynorphin A (1-17), and DOR AS oligo given i.t. daily for 3 days prevented the attenuation of i.t.-challenged [D-Ala2]deltorphin II-induced antinociception caused by the DOR AS oligo pretreatment. Our results support the existence of a turnover of delta-opioid receptors in the mouse spinal cord caused by the release of Met-enkephalin.

Animals↗

PubMed1997

Antisense oligodeoxynucleotide to delta opioid receptors blocks cocaine-induced place preference in mice.

The effect of intracerebroventricular (i.c.v.) treatment with antisense oligodeoxynucleotide (A-oligo) to delta opioid receptor mRNA on cocaine-induced place preference was examined in mice. Cocaine (10 mg/kg, s.c.) produced a significant place preference. I.c.v. treatment with A-oligo (0.001-1 microg/mouse) dose-dependently attenuated the cocaine (10 mg/kg, s.c.)-induced place preference, although mismatched oligodeoxynucleotide (1 microg/mouse, i.c.v.) was ineffective. In the present study, we found that the selective reduction in number and/or function of central delta opioid receptors by A-oligo suppresses the cocaine-induced place preference. These results suggest that the conditioned reward by cocaine may be partially mediated by central delta opioid receptors.

Animals↗

PubMed1997

[Met5]enkephalin and delta2-opioid receptors in the spinal cord are involved in the cold water swimming-induced antinociception in the mouse.

Mice made cold water swimming (CWS: 4 degrees C, 3 min) produced an opioid-mediated antinociception. Experiments were designed to determine what types of opioid receptors and endogenous opioid peptides in the spinal cord are involved in the CWS-induced antinociception in male ICR mice. Antinociception was measured by the tail-flick test. CWS-induced antinociception was blocked by intrathecal (i.t.) pretreatment with antiserum to [Met5]enkephalin (100 microg, 1 hr), but not by antiserum (100 microg, 1 hr) to [Leu5]enkephalin, beta-endorphin or dynorphin A (1-17). Moreover, i.t. pretreatment with delta2-opioid receptor antagonist naltriben (NTB: 10 microg, 10 min) blocked the antinociception induced by CWS or i.t.-administered [Met5]enkephalin (10 microg). However, the antinociception induced by CWS or i.t.-administered [Met5]enkephalin was not blocked by i.t. pretreatment with delta1-opioid receptor antagonist 7-benzylidene naltrexone (BNTX: 1 microg, 10 min), mu-opioid receptor antagonist D-Phe-Cys-Try-D-Try-Om-Thr-Phe-Thr-NH2 (CTOP: 50 ng, 10 min), or kappa-opioid receptor antagonist norbinaltorphimine (norBNI: 5 microg, 24 hr). These data indicate that [Met5]enkephalin and delta2-opioid receptor in the spinal cord are involved in antinociception induced by CWS.

Animals↗

PubMed1997

Antisense oligodeoxynucleotide to delta opioid receptors attenuates morphine dependence in mice.

The effect of intracerebroventricular (i.c.v.) treatment with antisense oligodeoxynucleotide (A-oligo) to delta opioid receptor mRNA on the morphine-induced place preference and naloxone-precipitated jumping was examined in morphine-dependent mice. Morphine (5 mg/kg, s.c.) produced a significant place preference. I.c.v. pretreatment with A-oligo (0.01-1 microg/mouse) dose-dependently attenuated this morphine (5 mg/kg, s.c.)-induced place preference, while mismatched oligodeoxynucleotide (M-oligo; 1 microg/mouse, i.c.v.) was ineffective. Naloxone (3 mg/kg, s.c.) precipitated jumping in morphine-dependent mice. I.c.v. pretreatment with A-oligo (1 microg/mouse) attenuated this naloxone (3 mg/kg, s.c.)-precipitated jumping in morphine-dependent mice, while M-oligo (1 microg/mouse, i.c.v.) was ineffective. These data demonstrate that the selective reduction in supraspinal delta opioid receptor function caused by pretreatment with A-oligo attenuated the morphine-induced place preference and naloxone-precipitated jumping in morphine-dependent mice, suggesting that the rewarding effect of and physical dependence on morphine may be modulated by central delta opioid receptors.

Animals↗

PubMed1997

Pretreatment with protein kinase C activator phorbol 12,13-dibutyrate attenuates the antinociception induced by mu- but not epsilon-opioid receptor agonist in the mouse.

The effects of pretreatment with a protein kinase C activator, phorbol 12,13-dibutyrate, on antinociception induced by i.c.v.-administered mu-opioid receptor agonist (D-Ala2, NMePhe4, Gly(ol)5) enkephalin (DAMGO) or morphine and epsilon-opioid receptor agonist beta-endorphin were studied in male ICR mice. The tail-flick responses were used for antinociceptive tests. I.c.v. pretreatment with phorbol 12,13-dibutyrate (50 pmol) for 30 or 60 but not 10 min attenuated antinociception induced by i.c.v.-administered DAMGO. I.c.v. pretreatment with phorbol 12,13-dibutyrate (10 and 50 pmol) for 60 min caused a dose-dependent attenuation of DAMGO (19.5 pmol)- or morphine (6.0 nmol)-induced antinociception. The dose-response curve for DAMGO-induced antinociception was shifted to the right by 7.3-fold by i.c.v. pretreatment with phorbol 12,13-dibutyrate (50 pmol) for 60 min. However, the i.c.v.-administered beta-endorphin-induced antinociception was not affected by the same pretreatment with phorbol 12,13-dibutyrate. The attenuation of i.c.v.-administered DAMGO- and morphine-induced antinociception by phorbol 12,13-dibutyrate was reversed by concomitant i.c.v. pretreatment with a selective protein kinase C inhibitor calphostin C. These results suggest that activation of protein kinase C by phorbol 12,13-dibutyrate leads to the desensitization of mu-, but not epsilon-opioid receptor-mediated antinociception. These findings also provide additional evidence for differential intracellular modulation on antinociceptive action of mu- and epsilon-opioid receptor agonists.

Analgesics↗

PubMed1997

Inhibition of spinal nitric oxide synthase by N(omega)-nitro-L-arginine blocks the release of Met-enkephalin and antinociception induced by supraspinally administered beta-endorphin in the rat.

The antinociception induced by beta-endorphin given supraspinally has been demonstrated previously to be mediated by the release of Met-enkephalin acting on delta2-opioid receptors in the spinal cord. The present study was designed to determine the role of nitric oxide in the spinal cord on beta-endorphin-induced release of Met-enkephalin and antinociception. The experiments were performed in pentobarbital-anesthetized rats. The release of Met-enkephalin was performed using a spinal cord perfusion technique and the Met-enkephalin released in the spinal perfusates was measured by radioimmunoassay. Antinociception was assessed by the tail-flick test. beta-Endorphin (2 microg) given intraventricularly induced the release of Met-enkephalin from the spinal cord. The release of Met-enkephalin was dose-dependently attenuated by N(omega)-nitro-L-arginine (0.1 nM-1 microM) added into spinal perfusates and the attenuation was reversed by intrathecally applied L-arginine. The stereoisomer N(omega)-nitro-D-arginine given intrathecally, however, did not inhibit the release of Met-enkephalin induced by intraventricularly administered beta-endorphin. beta-Endorphin (4 microg) given intraventricularly produced antinociception in rats pretreated intrathecally with saline. The antinociception induced by beta-endorphin was blocked by intrathecally administered N(omega)-nitro-L-arginine (5 microg) and the blockade of antinociception was reversed by intrathecal injection of L-arginine (50 microg). N(omega)-Nitro-D-arginine (5 microg) given intrathecally did not block the intraventricularly administered beta-endorphin-induced antinociception. N(omega)-Nitro-L-arginine (10 microg) given intraventricularly did not affect intraventricularly administered beta-endorphin-induced Met-enkephalin release nor did it affect intraventricular beta-endorphin-induced antinociception, indicating that the effect of N(omega)-nitro-L-arginine is not at supraspinal sites. Intrathecal pretreatment with N(omega)-nitro-L-arginine did not affect intrathecally administered [D-Ala2]deltorphin II-induced antinociception. Our results indicate that N(omega)-nitro-L-arginine given intrathecally attenuates intraventricular beta-endorphin-administered inhibition of the tail-flick response by presynaptically inhibiting the release of Met-enkephalin.

Analgesics↗

PubMed1997

[Met]enkephalin in the spinal cord is involved in the antinociception induced by intracerebroventricularly-administered etorphine in the mouse.

We have recently reported that the antinociception induced by etorphine given i.c.v. is mediated in part by the stimulation of both mu- and epsilon-opioid receptors and the activation of both monoaminergic and opioidergic descending pain control systems. [Xu J. Y. et al. (1992) J. Pharmac. exp. Ther. 263, 246-252]. Since the opioid epsilon-receptor-mediated antinociception induced by beta-endorphin is mediated by the release of [Met]enkephalin and subsequent stimulation of delta-opioid receptors in the spinal cord, the present studies were designed to determine if beta-endorphin-like action is also involved in etorphine-induced antinociception. The tail-flick test was used to assess the antinociceptive response performed in male ICR mice. Etorphine at doses from 5 to 20 ng given i.c.v. produced a dose-dependent inhibition of the tail-flick response. The inhibition of the tail-flick response induced by etorphine given i.c.v. was antagonized by intrathecal pretreatment for 60 min with antiserum against [Met]enkephalin (10 microg), but not with antiserum against [Leu]enkephalin (10 microg) or dynorphin A (1-13) (10 microg). Desensitization of delta-opioid receptors in the spinal cord by intrathecal pretreatment with [Met]enkephalin (5 microg) for 60 min attenuated i.c.v. administered etorphine-induced tail-flick inhibition. However, intrathecal pretreatment with [Leu]enkephalin (5 microg) or dynorphin A (1-17) (0.1 microg) for 60 min did not attenuate i.c.v. administered etorphine-induced tail-flick inhibition. The results indicate that antinociception induced by etorphine given i.c.v. is mediated in part by the stimulation of the epsilon-opioid receptor at the supraspinal sites and by the release of [Met]enkephalin, which subsequently stimulates delta-opioid receptors in the spinal cord.

Analgesics, Opioid↗

PubMed1997

The effect of pretreatment with a delta 2-opioid receptor antisense oligodeoxynucleotide on the recovery from acute antinociceptive tolerance to delta 2-opioid receptor agonist in the mouse spinal cord.

1. An intrathecal (i.t.) injection of a selective delta 2-opioid receptor agonist, [D-Ala2]deltorphin II, produced an acute antinociceptive tolerance to the antinociceptive effect of a subsequent i.t. challenge of [D-Ala2]deltorphin II. This acute tolerance lasted 3 to 9 h and completely subsided by 12 h. The experiments were designed to examine the effect of pretreatment with an antisense oligodeoxynucleotide to delta 2-opioid receptor mRNA (delta-AS oligo) on the recovery from tolerance to [D-Ala2]deltorphin II-induced antinociception in male ICR mice. 2. Pretreatment with delta-AS oligo (1.63 to 163 pmol, i.t.), but not mismatched oligo (MM oligo) (163 pmol), prevented the recovery from acute tolerance to [D-Ala2]deltorphin II-induced antinociception in a dose-dependent manner. However, treatment with delta-AS oligo (163 pmol) did not prevent the recovery from tolerance to either the mu-opioid receptor agonist [D-Ala2,NMePhe4,Gly(ol)5]enkephalin (DAMGO) or the kappa-opioid receptor agonist U50,488H, indicating subtype specificity in the mechanism by which delta-AS oligo inhibits recovery from delta 2-opioid tolerance. 3. Treatment with [D-Ala2]deltorphin II (i.t.) significantly reduced the binding of [tyrosyl-3,5-(3)H(N)]-Tyr-D-Ser-Gly-Phe-Leu-Thr ([3H]-DSLET), a delta 2-opioid receptor agonist ligand, in the spinal cord 3 h after treatment, but binding returned to control levels by 24 h after treatment. However, [3H]-DSLET binding in the spinal cord remained significantly reduced at 24 h if delta-AS oligo (163 pmol) was coadministered with [D-Ala2]deltorphin II (6.4 nmol). 4. Based on these findings, it is concluded that a single stimulation of spinal cord delta 2-opioid receptors by intrathecally-administered [D-Ala2]deltorphin II induces a long-lasting desensitization of delta 2-opioid receptors to [D-Ala2]deltorphin II. Recovery from delta 2-opioid receptor-mediated antinociceptive tolerance apparently depends on replenishment by newly synthesized delta 2-opioid receptor protein rather than immediate reversal of delta 2-opioid receptors.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed1997

Delta-1 opioid receptor-mediated antinociceptive properties of a nonpeptidic delta opioid receptor agonist, (-)TAN-67, in the mouse spinal cord.

The effects of enantiomorphs of TAN-67 (2-methyl-4a alpha-(3-hydroxyphenyl)-1,2,3,4,4a,5,12,12a alpha-octahydro-quinolino[2,3,3-g]isoquinoline), (-)TAN-67 and (+)TAN-67, given intrathecally (i.t.) on antinociceptive response with the tail-flick test were studied in male ICR mice. (-)TAN-67 at doses from 17.9 to 89.4 nmol given i.t. produced a dose- and time-dependent inhibition of the tail-flick response, whereas its enantiomer (+)TAN-67 even at smaller doses (1.8, 4.5 and 8.9 nmol) given i.t. decreased the latencies of the tail-flick response. In addition, (+)TAN-67 at higher doses (17.9-89.4 nmol) given i.t. produced scratching and biting pain-like responses. The antinociceptive response induced by i.t.-administered (-)TAN-67 was mediated by the stimulation of delta-1 but not by delta-2, mu or kappa opioid receptors, because the effect was blocked by the i.t. pretreatment with BNTX, but not by naltriben, [D-Phe-Cys-Tyr-[D-Try-Orn-Thr-Pen-Thr-NH2 or nor-binaltorphimine dihydrochloride. Pretreatment with (-)TAN-67 given i.t. 3 hr earlier attenuated the tail-flick inhibition induced by subsequent i.t. administration of (-)TAN-67 and by [D-Pen2,5]enkephalin (DPDPE). However, the tail-flick inhibition induced by [D-Ala2]deltorphin II, [D-Ala2,NMePhe4,Gly5-ol]enkephalin and U50,488H were not affected by (-)TAN-67 pretreatment. Conversely, pretreatment with DPDPE given i.t. 3 hr earlier attenuated the tail-flick inhibition induced by subsequent i.t. administration of (-)TAN-67 and by DPDPE. However, the tail-flick inhibition induced by [D-Ala2]deltorphin II was not affected by i.t. DPDPE pretreatment. It is concluded that (-)TAN-67 given i.t. produces delta-1 opioid receptor-mediated antinociception; on the other hand, its enantiomer (+)TAN-67 produces hyperalgesia. Present studies provide other evidence that delta-1 opioid receptors exist separated from delta-2 opioid receptor.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed1996

Hyperalgesia induced by pituitary adenylate cyclase-activating polypeptide in the mouse spinal cord.

The aim of the present study was to evaluate the distribution of pituitary adenylate cyclase-activating polypeptide (PACAP)-like immunoreactivity in the mouse spinal cord using an antibody against PACAP38 and to determine the behavioral profile, particularly with respect to hyperalgesia, of PACAP38 given intrathecally (i.t.) in the mouse. Immunoreactivity to PACAP38 was detected in numerous nerve fibers in the superficial layers of the dorsal horn of cervical, thoracic, lumbar and sacral segments and a few fibers extended into the deeper layers of the spinal cord. In addition, PACAP-like immunoreactivity were seen in the intermediolateral cell column of the thoracic and sacral segments. In behavioral studies, PACAP38 (0.05-0.5 microgram) produced a dose-dependent decrease of the tail-flick latency when given i.t. in the mouse. At higher doses (1-10 micrograms), PACAP38 given i.t. elicited biting and scratching behaviors lasting 10-20 min after the injection. PACAP at high doses (1-10 micrograms) also produced licking at tail, paw and penis and intense grooming behaviors immediately after the i.t. injection. Similar to substance P, these behaviors produced by PACAP can be considered as pain-like syndrome. These findings suggest that PACAP may be a sensory neurotransmitter involved in nociceptive signalling in the mouse spinal cord.

Animals↗

PubMed1996

Phorbol ester blocks the increase of a high affinity GTPase activity induced by delta 2-opioid receptor agonist in the mouse spinal cord.

The high affinity GTPase activity in the mouse spinal cord was increased in a concentration-dependent manner by a selective delta 2-opioid receptor agonist, [D-Ala2]deltorphin II (0.1-1 microM). This increase of GTPase activity induced by [D-Ala2]deltorphin II was completely blocked by co-incubation with a selective delta 2-opioid receptor antagonist, naltriben (0.1 microM). A protein kinase C activator, phorbol 12,13-dibutyrate (PDB; 0.1-10 microM), which given alone had no effect on basal GTPase activity, blocked dose-dependently the increase of GTPase activity induced by [D-Ala2]deltorphin II (1 microM). Our results indicate the possibility that activation of protein kinase C by phorbol ester uncouples the delta 2-opioid receptor from G-proteins in the spinal cord.

Animals↗

PubMed1996

Pretreatment with pertussis toxin spinally, but not supraspinally, blocks the cold water swimming-induced antinociception in the mouse.

Mice exposed to cold water swimming (4 degrees C) for 3 min produced a marked antinociception. Experiments were designed to determine whether pretreatment with pertussis toxin given intrathecally (i.t.) or intracerebroventricularly (i.c.v.) attenuates cold water swimming-induced antinociception in male ICR mice. Antinociception was measured by the tail-flick test 7 min after cold water swimming. I.t. pretreatment with pertussis toxin at a dose of 0.5 microgram for 24-96 h caused a time-dependent attenuation of cold water swimming-induced antinociception. Moreover, i.t. pretreatment with pertussis toxin at doses from 0.125 to 0.5 microgram for 96 h attenuated cold water swimming-induced antinociception in a dose-dependent manner. However, i.c.v. pretreatment with pertussis toxin at doses from 0.125 to 0.5 microgram for 24-96 h did not affect the cold water swimming-induced antinociception. The present results suggest that pertussis toxin-sensitive Gi/G(o) proteins in spinal cord, but not at the supraspinal sites, are involved in cold water swimming-induced antinociception.

Animals↗

PubMed1996

Use of antisense oligodeoxynucleotide to determine delta-opioid receptor involvement in [D-Ala2]deltorphin II-induced locomotor hyperactivity.

Intracerebroventricularly (i.c.v.)-administered [D-Ala2]deltorphin II (20 micrograms) produced a marked locomotor hyperactivity in male ICR mice. The locomotor hyperactivity induced in response to i.c.v. [D-Ala2]deltorphin II (20 micrograms) was suppressed by pretreatment with naltriben (NTB, 10 micrograms) but not 7-benzylidene naltrexone (BNTX, 1 microgram) and D-Phe-Cys-Tyr-D-Try-Orn-Thr-Phe-Thr-NH2 (CTOP, 100 ng). The influence of antisense oligodeoxynucleotide to delta-opioid receptor mRNA (delta-AS oligo) or a mismatch oligodeoxynucleotide (MM oligo) on the locomotor hyperactivity induced by [D-Ala2]deltorphin II was determined. Groups of mice pretreated i.c.v. with delta-AS oligo (1 microgram), MM oligo (1 microgram) or saline (4 microliters) once a day for 3 days, were injected i.c.v. [D-Ala2]deltorphin II (10 or 20 micrograms) and the locomotor response to [D-Ala2]deltorphin II was measured. The locomotor hyperactivity of i.c.v. [D-Ala2]deltorphin II (10 or 20 micrograms) were significantly suppressed by i.c.v. pretreatment with delta-AS oligo but not MM oligo. The present results indicate that pretreatment with delta-AS oligo suppresses mouse locomotor hyperactivity produced by stimulation of delta 2-opioid receptors in the brain.

Amino Acid Sequence↗

PubMed1996

Antisense oligodeoxynucleotide to a delta-opioid receptor messenger RNA selectively blocks the antinociception induced by intracerebroventricularly administered delta-, but not mu-, epsilon- or kappa-opioid receptor agonists in the mouse.

An antisense oligodeoxynucleotide to delta-opioid receptor messenger RNA was utilized to block the expression of mouse delta-opioid receptors for antinociception. The antinociception was measured by the tail-flick test in male ICR mice. Pretreatment with delta-antisense oligodeoxynucleotide (163 pmol) given intracerebroventricularly twice a day for one to four days produced a time-dependent inhibition of the tail-flick response induced by intracerebroventricularly administered (D-Ala2)deltorphin II (12.8 nmol). The (D-Ala2)deltorphin II-induced antinociception was significantly attenuated after three to four days of the delta-antisense oligodeoxynucleotide treatment, remained attenuated for two days and gradually recovered to the control level in four to 10 days after cessation of the pretreatment with delta-antisense oligodeoxynucleotide. Pretreatment with delta-antisense oligodeoxynucleotide (163 pmol) twice a day for four days markedly attenuated the antinociception induced by intracerebroventricularly administered (D-Ala2)deltorphin II and, to a lesser extent, by D-Pen2-D-Pen5-enkephalin and morphine, but not by (D-Ala2-MePhe4-Gly(ol)5)enkephalin, beta-endorphin or U50,488H. Mismatched oligodeoxynucleotide (163 pmol) was ineffective against the antinociception induced by these opioids. Our results provide the evidence that the cloned delta-opioid receptor is related to the pharmacologically classified delta 2-opioid receptor, and the antinociception induced by (D-Ala2)deltorphin II and, at least in part, by D-Pen2-D-Pen5-enkephalin and morphine given intracerebroventricularly is mediated by the stimulation of delta 2-opioid receptors. However, delta 2-opioid receptors are not involved in the antinociception induced by beta-endorphin, (D-Ala2-MePhe4-Gly(ol)5)enkephalin or U50,488H given intracerebroventricularly.

Animals↗

PubMed1996

Role of protein kinase C in desensitization of spinal delta-opioid-mediated antinociception in the mouse.

1. Receptor phosphorylation and down-regulation by protein kinases may be a key event initiating desensitization. The present studies were designed to investigate the effect of a potent protein kinase C (PKC) activator, phorbol 12,13-dibutyrate (PDBu), on antinociception induced by intrathecal (i.t.) administration of a selective delta-opioid receptor agonist [D-Ala2] deltorphin II in the male ICR mouse and on the specific binding of [3H]-[D-Ser2, Leu5]enkephalin-Thr6 (DSLET), a delta-opioid receptor ligand, in the crude synaptic membrane of the spinal cord. 2. Intrathecal (i.t.) pretreatment with PDBu at low doses, which injected alone did not affect the basal tail-flick latency, dose-dependently attenuated the antinociception induced by i.t. administration of [D-Ala2]deltorphin II. The attenuation of i.t.-administered [D-Ala2] deltorphin II-induced antinociception by PDBu was reversed in a dose-dependent manner by i.t. concomitant pretreatment with a specific PKC inhibitor, calphostin C. 3. In the binding experiment, incubation of the crude synaptic membrane of the spinal cord for 2 h at 25 degrees C with PDBu (0.03 to 10 microM) caused a dose-dependent inhibition of the [3H]-DSLET binding. Scatchard analysis of [3H]-DSLET binding revealed that PDBu at 10 microM displayed a 30.7% reduction in the number of [3H]-DSLET binding sites with no significant change in affinity, compared with the non-treatment control, indicating that the activation of membrane-bound PKC by PDBu causes a decrease in the number of specific delta-opioid agonist binding sites. 4. An i.t. injection of [D-Ala2]deltorphin II produced an acute antinociceptive tolerance to the antinociceptive effect of a subsequent i.t. challenge of [D-Ala2]deltorphin II. Concomitant pretreatment with calphostin C markedly prevented the development of acute tolerance to the i.t.-administered [D-Ala2]deltorphin II-induced antinociception. On the other hand, a highly selective protein kinase A (PKA) inhibitor, KT5720, did not have any effect on the development of acute tolerance to [D-Ala2]deltorphin II antinociception. 5. These findings suggest that a loss of specific delta-agonist binding by the activation of PKC by PDBu is involved in the PDBu-induced antinociceptive unresponsiveness to delta-opioid receptor agonist in the mouse spinal cord. Based on the acute tolerance studies, we propose that PKC, but not PKA, plays an important role in the process of homologous desensitization of the spinal delta-opioid receptor-mediated antinociception.

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