Inhibition of osteoclasts prevents cartilage loss and pain in a rat model of degenerative joint disease

OBJECTIVE

To investigate the relationship between efficacy of a bisphosphonate, pain and extent of joint damage in the monosodium iodoacetate (MIA) model of painful degenerative joint disease.

METHODS

Zoledronate treatment was initiated prior to and at various times following model induction, including late time points representing advanced disease. Radiographic and histological structural parameters were correlated with pain as measured by weight bearing.

RESULTS

Intraarticular (IA) MIA resulted in a progressive loss of bone mineral density (BMD) and chondrocytes, thinning of cartilage, loss of proteoglycan, resorption of calcified cartilage and subchondral bone, as well as pain. This was completely prevented by pre-emptive chronic zoledronate treatment with joint sections being histologically indistinguishable from saline-injected controls. When initiation of treatment was delayed efficacy was reduced. In animals with advanced joint degeneration, treatment partially restored BMD and had a significant, but limited, effect on pain. We confirmed these radiographic and behavioral findings in the medial meniscal tear model. To understand the mechanism-of-action of zoledronate we investigated an early time point 4 days post-model induction when chondrocytes were histologically viable, with minor loss of proteoglycan and generalized synovitis. Osteoclast-mediated resorption of the calcified cartilage was observed and was prevented by two doses of zoledronate.

CONCLUSION

Subchondral bone remodeling plays an important role in nociception and the pathobiology of the MIA model with osteoclasts being implicated in both bone and cartilage resorption. Inhibition of osteoclastic activity when initiated early leads to improved efficacy.

WAY-318068: a novel, potent and selective noradrenaline re-uptake inhibitor with activity in rodent models of pain and depression

BACKGROUND AND PURPOSE

Antidepressants, which raise the CNS concentrations of 5-HT and noradrenaline, are frequently used in the treatment of chronic pain; however, it is not known if increasing CNS noradrenaline levels alone is sufficient for efficacy, in part resulting from a lack of small molecules with sufficient selectivity.

EXPERIMENTAL APPROACH

In this report, we present the in vitro pharmacological and in vivo pharmacokinetic and pharmacological properties of the novel, orally available and CNS penetrant inhibitor of the noradrenaline transporter (NET), WAY-318068 (1-[(1S,2R)-1-(3,5-difluorophenyl)-2-hydroxy-3-(methylamino)propyl]-7-fluoro-3,3-dimethyl-1,3-dihydro-2H-indol-2-one).

KEY RESULTS

WAY-318068 is a potent and effective inhibitor of the NET with a K(i) of 8.7 nM in a binding assay, and an IC(50) of 6.8 nM in an assay of transporter function, without significant binding to the dopamine transporter. Furthermore, the compound has only weak activity at the 5-HT transporter, leading to a functional selectivity of greater than 2500-fold. It is orally bioavailable with substantial quantities of the compound found in the CNS after oral dosing. As measured by microdialysis in rats, the compound causes a robust and significant increase in cortical noradrenaline levels without affecting 5-HT. WAY-318068 was effective in models of acute, visceral, inflammatory, osteoarthritic, neuropathic, diabetic and bone cancer pain, as well as in traditional models of depression at doses that do not cause motor deficits.

CONCLUSIONS AND IMPLICATIONS

Collectively, the present results support the conclusion that selectively increasing CNS levels of noradrenaline is sufficient for efficacy in models of depression and pain.

Concerning the statistical procedures enumerated by Gentile et al.: another perspective

The thrust of this paper is to bring to the attention of operant researchers statistical procedures that are appropriate for correlated data. In addition to specifying these statistical procedures consideration is given to the question of using individual comparison statistics rather than omnibus F tests. Specifically, it is recommended that a more powerful test of the experimental hypotheses can be obtained by performing Bonferroni t statistics rather than analysis of variance F tests.

Predictive validity of animal pain models? A comparison of the pharmacokinetic-pharmacodynamic relationship for pain drugs in rats and humans

A number of previous reviews have very eloquently summarized pain models and endpoints in animals. Many of these reviews also discuss how animal models have enhanced our understanding of pain mechanisms and make forward-looking statements as to our proximity to the development of effective mechanism-based treatments. While a number of reports cite failures of animal pain models to predict efficacy in humans, few have actually analyzed where these models have been successful. This review gives a brief overview of those successes, both backward, providing validation of the models, and forward, predicting clinical efficacy. While the largest dataset is presented on treatments for neuropathic pain, this review also discusses acute and inflammatory pain models. Key to prediction of clinical efficacy is a lack of side effects, which may incorrectly suggest efficacy in animals and an understanding of how pharmacokinetic parameters translate from animals to man. As such, this review focuses on a description of the pharmacokinetic-pharmacodynamic relationship for a number of pain treatments that are effective in both animals and humans. Finally we discuss where and why animal pain models have failed and summarize improvements to pain models that should expand and improve their predictive power.

Combining the Locator System with WinID3--identifying victims from dental remains in a large disaster

Computer software programs are typically used at disaster sites to help identify victims from dental remains. Using a simulated disaster with 300 simulated victims and 105 simulated dental fragments, previous research compared two computer programs, WinID and CAPMI4, to a non-computer identification system--the Locator System (LS). LS performed best. LS requires dental professionals manually to sort antemortem and postmortem files into dental categories and then compare postmortem and antemortem files in the same category to find matches. We combined LS with the better of the two computer programs, WinID, to create a single method. This method was used by two teams of forensic odontologists to identify victims in the same simulated disaster employed in previous research. One team had 8 members and the other had 5 members. The 5-member team performed better than all previous teams and the 8-member team performed better than the 5-member team. The 8-member team was large enough to assign a different member to each category as a specialist. We make practical recommendations on identifying disaster victims from dental remains.

Answering two criticisms of hypothesis testing: reply to Serlin

Two criticisms of hypothesis testing have been repeated for half a century. Leventhal (1999) defended against those criticisms. Serlin (2000) commented on Leventhal's paper and criticized parts of Leventhal's defense. Serlin's comments are discussed and his criticisms answered.

Neurodegeneration prevented by lentiviral vector delivery of GDNF in primate models of Parkinson's disease

Lentiviral delivery of glial cell line-derived neurotrophic factor (lenti-GDNF) was tested for its trophic effects upon degenerating nigrostriatal neurons in nonhuman primate models of Parkinson's disease (PD). We injected lenti-GDNF into the striatum and substantia nigra of nonlesioned aged rhesus monkeys or young adult rhesus monkeys treated 1 week prior with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Extensive GDNF expression with anterograde and retrograde transport was seen in all animals. In aged monkeys, lenti-GDNF augmented dopaminergic function. In MPTP-treated monkeys, lenti-GDNF reversed functional deficits and completely prevented nigrostriatal degeneration. Additionally, lenti-GDNF injections to intact rhesus monkeys revealed long-term gene expression (8 months). In MPTP-treated monkeys, lenti-GDNF treatment reversed motor deficits in a hand-reach task. These data indicate that GDNF delivery using a lentiviral vector system can prevent nigrostriatal degeneration and induce regeneration in primate models of PD and might be a viable therapeutic strategy for PD patients.

Cyclosporin A protects striatal neurons in vitro and in vivo from 3-nitropropionic acid toxicity

The neuroprotective properties of cyclosporin A (CsA) are mediated by its ability to prevent mitochondrial permeability transition during exposure to high levels of calcium or oxidative stress. By using the mitochondrial toxin 3-nitropropionic acid (3NP), the present study assessed whether CsA could protect striatal neurons in vitro and in vivo. In vitro, 3NP produced a 20-30% reduction of striatal glutamic acid decarboxylase-immunoreactive (GAD-ir) neurons. A single treatment with CsA protected GAD-ir neurons from 3NP toxicity at lower (0.2 or 1.0 microM), but not at higher (5.0 microM) doses. Similar findings were seen when the cultures were treated twice with cyclosporin. In vivo experiments used the Lewis rat model of Huntington's disease (HD) in which a low 3NP dose was delivered subcutaneously through an osmotic minipump. Rats received unilateral or bilateral intrastriatal saline injections to disrupt the blood-brain barrier (BBB) and facilitate CsA reaching vulnerable neurons. In the first experiment, CsA treated 3NP-lesioned rats displayed significantly more dopamine-and adenosine-3;, 5;-monophosphate-regulated phosphoprotein (DARPP32-ir) neurons ipsilateral to BBB disruption compared to the contralateral intact striatum, indicating that disruption of the BBB maybe necessary for CsA's neuroprotective effects. In the second experiment, stereological counts of DARPP32-ir neurons revealed that CsA protected striatal neurons in a dose-dependent manner following bilateral disruption of the striatal BBB. Rats treated with the higher (15 or 20 mg/kg) but not lower (5 mg/kg) doses of CsA displayed greater numbers of DARRP32-ir striatal neurons relative to vehicle-treated 3NP-lesioned rats. Thus, under conditions in which CsA can gain access to striatal neurons, significant protection from 3NP toxicity is observed. Therefore, CsA or more lipophilic analogues of this compound, may be of potential therapeutic benefit by protecting vulnerable neurons from the primary pathological event observed in HD.

Delayed onset of progressive dystonia following subacute 3-nitropropionic acid treatment in Cebus apella monkeys

Delayed abnormal movements can be observed in patients with acute neurologic insult after a prolonged period of apparent neurologic stability. To reproduce such a secondary neurologic manifestation in primates, the present experiment investigated whether systemic administration of subacute 3-nitropropionic acid (3NP), a mitochondrial toxin, could induce abnormal movements that were delayed and progressive over time. Four Cebus apella monkeys received systemic 3NP injections until acute neurologic signs manifested. The monkeys were regularly video-recorded and rated for abnormal movements for up to 15 weeks after the cessation of 3NP treatment. Five to 6 weeks after the 3NP treatment, monkeys displayed a significant increase in dyskinesias compared with pretreatment conditions. Over time the chorea attenuated, whereas the dystonic movements increased in intensity and severity which was characterized by a delayed decrease of peak tangential velocity. The intensity of abnormal movements and extent of affected body regions observed in each monkey were consistent with the size of basal ganglia hypersignal as documented by T2 sequence on magnetic resonance imaging. Thus, more severe motor impairments were associated with large magnetic resonance image abnormalities. This novel primate model may be particularly useful for studying the structural changes underlying delayed and progressive manifestations of abnormal movements with the ultimate goal of facilitating the evaluation of novel therapeutic strategies.

Morphine-6beta-glucuronide-induced hyperphagia: characterization of opioid action by selective antagonists and antisense mapping in rats

Opiate drugs such as morphine stimulate food intake in rats. The morphine metabolite, morphine-6beta-glucuronide (M6G), is more active than morphine in analgesic assays, and appears to act through distinct receptors. Thus, although morphine analgesia is decreased by antisense oligodeoxynucleotides (AS ODNs) targeting exons 1 and 4 of the MOR-1 clone, M6G analgesia is reduced by probes targeting exons 2 and 3 of the MOR-1 clone. Our study examined whether central administration of M6G increased food intake in rats, and characterized this response using either selective mu, kappa1, delta1 and delta2 antagonists, or antisense directed against the various cloned opioid receptors. Central M6G (10-1000 ng) significantly and dose-dependently increased intake after 4 hr. Whereas mu antagonism with betaFNA significantly and dose-dependently reduced M6G-induced hyperphagia, equimolar doses of delta1, delta2, and kappa1 antagonists were ineffective. AS ODNs directed against either exons 2 or 3 of the MOR-1 clone blocked M6G-induced hyperphagia, whereas either AS ODNs directed against exons 1 or 4, or a MS ODN directed against exon 2 were ineffective. In contrast, an AS ODN probe directed against exon 1, but not exon 2, of the MOR-1 clone reduced morphine-induced hyperphagia, an effect identical to DAMGO-induced hyperphagia. Whereas M6G-induced hyperphagia was insensitive to antisense probes directed against the DOR-1, KOR-1 and KOR-3/ORL1 clones, these probes respectively reduced hyperphagia induced by deltorphin II, U50488H and nociceptin. Although pharmacological data indicate that M6G-induced hyperphagia acts through mu receptors, antisense data imply that the hyperphagic actions of M6G are mediated by a receptor distinct from traditional mu agonists, either as an alternative splice variant of the MOR-1 clone or a distinct gene.

Pharmacological characterization of endomorphin-1 and endomorphin-2 in mouse brain

The recently isolated peptides endomorphin-1 and endomorphin-2 have been suggested to be the endogenous ligands for the mu receptor. In traditional opioid receptor binding assays in mouse brain homogenates, both endomorphin-1 and endomorphin-2 competed both mu1 and mu2 receptor sites quite potently. Neither compound had appreciable affinity for either delta or kappa1 receptors, confirming an earlier report. However, the two endomorphins displayed reasonable affinities for kappa3 binding sites, with Ki values between 20 and 30 nM. Both endomorphins competed 3H-[D-Ala2, MePhe4,Gly(ol)5] enkephalin binding to MOR-1 receptors expressed in CHO cells with high affinity. In mouse brain homogenates 125I-endomorphin-1 and 125I-endomorphin-2 binding was selectively competed by mu ligands. 125I-Endomorphin-1 and 125I-endomorphin-2 also labeled MOR-1 receptors expressed in CHO cells with high affinity. Autoradiography of the two 125I-labeled endomorphins demonstrated regional patterns in the brain similar to those previously observed for mu drugs. Pharmacologically, the endomorphins were potent analgesics. Although they were equipotent supraspinally, endomorphin-1 was more potent spinally. Endomorphin analgesia was effectively blocked by naloxone, as well as the mu-selective antagonists beta-funaltrexamine and naloxonazine. In CXBK mice, which are insensitive to supraspinal morphine, neither endomorphin was active, consistent with a mu mechanism of action. Finally, the endomorphins inhibited gastrointestinal transit. In conclusion, these results support the mu selectivity of these agents.

Orphan opioid receptor antisense probes block orphanin FQ-induced hyperphagia

Orphanin FQ/nociceptin binds with high affinity to the orphan opioid receptor-like/K-3 (ORL1/KOR-3) clone, and stimulates feeding. The present study demonstrated that antisense oligodeoxynucleotides directed against either exons 1, 2 or 3 of the ORL1/KOR-3 clone reduced orphanin FQ/nociceptin-induced hyperphagia. A missense probe was ineffective. Naltrexone dose-dependently reduced orphanin FQ/nociceptin-induced hyperphagia. These data suggest that the receptor responsible for orphanin FQ/nociceptin-induced hyperphagia is encoded by the ORL1/KOR-3 clone.

Orphanin FQ/nociceptin analgesia in the rat

The heptadecapeptide orphanin FQ or nociceptin (OFQ/N), the endogenous ligand for the orphan opioid receptor, has a complex pharmacology in mice, eliciting either an anti-opioid/hyperalgesic action or analgesia depending upon the dose and testing paradigm. Unlike mice, orphanin FQ/nociceptin fails to elicit hyperalgesia in the rat following intracerebroventricular injection. Both OFQ/N and a truncated version, OFQ/N(1-11), produce a robust analgesic response. OFQ/N analgesia is readily antagonized by the opioid antagonists naloxone or diprenorphine, despite their very poor affinity for the cloned orphan opioid receptor. Antisense studies revealed that probes targeting the second and third coding exon of the orphan clone significantly attenuate OFQ/N analgesia, while the exon 1 probe was inactive. These results indicate that OFQ/N elicits a naloxone-sensitive analgesia in rats similar to that previously reported in mice.

Antinociceptive analogs of orphanin FQ/nociceptin(1-11)

The presence of pairs of basic amino acids within the sequence of orphanin FQ/nociceptin (OFQ/N) peptide, the endogenous ligand for the ORL1/KOR-3 receptor, has raised the possibility that processing might generate pharmacologically important truncated peptides, including OFQ/N(1-11). OFQ/N(1-11) is pharmacologically active in vivo with a potency comparable to OFQ/N. Several tyrosine-containing analogs of OFQ/N(1-11) have been synthesized and examined for antinociceptive activity. Like OFQ/N(1-11), [Tyr1]OFQ/N(1-11), [Tyr10]OFQ/N(1-11) and [IodoTyr10]OFQ/N(1-11) given supraspinally in mice were antinociceptive in the tailflick assay in mice. The tyrosine analogs showed similar potencies as OFQ/N(1-11) but longer durations of action. This response was readily reversed by the opioid antagonist naloxone despite poor affinities for these analogs at opioid receptors. Another compound, [Tyr11]OFQ/N(1-11) was highly epileptogenic, inducing naloxone-sensitive seizures in greater than 50% of the mice tested at doses comparable to those examined with the other analogs. These results indicate that it is possible to make analgesic OFQ/N(1-11) analogs. The activity of [IodoTyr10]OFQ/N(1-11) suggests that it may prove useful as a radioligand in exploring potential OFQ/N(1-11) binding sites.

Antisense mapping of the MOR-1 opioid receptor clone: modulation of hyperphagia induced by DAMGO

The mu opioid receptor mediates ingestive behavior: mu-selective agonists stimulate food intake and antagonists reduce intake in many ingestive situations. Antisense oligodeoxynucleotides directed against each of the four exons of the MOR-1 clone were equally effective in reducing spontaneous food intake and body weight in rats. However, antisense probes directed against only exon 1 or 4 of the MOR-1 clone reduced mu-mediated analgesia. The present study examined whether central administration of antisense probes directed against each of the four exons of the MOR-1 clone or a missense control altered hyperphagia elicited by the mu agonist DAMGO across a range of doses. Antisense probes directed against only exon 1 or 4 blocked hyperphagia at agonist doses of 0.5 and 1.0 microg; this pattern was identical to that observed for mu-mediated analgesia. A missense control failed to exert significant effects, which suggests specificity of antisense actions. The effective antisense probes failed to reduce hyperphagia at a higher (5 microg) agonist dose, a result consistent with limitations in down-regulation of receptor proteins by antisense. The mu antagonist beta-funaltrexamine produced a similar pattern of effects on mu-mediated hyperphagia. The selective actions of antisense probes directed against different exons of the MOR-1 clone in reducing hyperphagia induced by DAMGO suggest that multiple splice variants of the MOR-1 clone exist and raise the possibility of further opioid receptor subclassifications.

Pharmacological characterization of orphanin FQ/nociceptin and its fragments

The cloning of a fourth member of the opioid receptor family has led to the discovery of a new neuropeptide termed orphanin FQ or nociceptin (OFQ/N). Studies in CD-1 mice confirm the ability of OFQ/N to rapidly induce hyperalgesia within 15 min which is insensitive to opioid antagonists. This is followed in the next 30 min by loss of hyperalgesia and the appearance of analgesia in the tailflick assay which is readily reversed by opioid antagonists. However, the very poor affinity of OFQ/N for all the traditional opioid receptors and the insensitivity of OFQ/N analgesia to antisense oligodeoxynucleotides active against MOR-1, DOR-1 or KOR-1 sequences that selectively block mu, delta or kappa1 analgesia, respectively, make it unlikely that OFQ/N analgesia is mediated through typical opioid receptors. Blockade of the antiopioid sigma system by haloperidol enhances the analgesic potency of OFQ/N of more than 100-fold. This effect is pronounced in BALB-C and Swiss-Webster mice. Although OFQ/N alone has little analgesic activity in these mice, the blockade of sigma systems with haloperidol uncovers a robust analgesic response in both strains. Two shorter OFQ/N fragments, OFQ/N(1-7) and OFQ/N(1-11), also are analgesic in CD-1 mice and their actions are reversed by the opioid antagonist diprenorphine despite very poor affinities of both peptides against [125I]OFQ/N binding and all the opioid receptors. In antisense studies, a probe targeting the first coding exon of KOR-3 eliminates OFQ/N hyperalgesia, but not OFQ/N analgesia. Conversely, antisense probes based on the second and third coding exons are inactive against OFQ/N hyperalgesia but readily reverse kappa3 opioid analgesia. These results suggest that OFQ/N elicits both analgesia and hyperalgesia through pharmacologically distinct receptors that do not correspond to traditional opioid receptors.

3-Methoxynaltrexone, a selective heroin/morphine-6beta-glucuronide antagonist

Recent work has suggested that heroin and morphine-6beta-glucuronide (M6G) both act through a novel mu opioid receptor subtype distinct from those mediating morphine's actions. This very high affinity 3H-M6G site is selectively competed by 3-methoxynaltrexone. In vivo, 3-methoxynaltrexone (2.5 ng, i.c.v.) selectively antagonizes the analgesic actions of heroin and M6G without interfering with mu (morphine and [D-Ala2,MePhe4,Gly(ol)5]enkephalin), delta ([D-Pen2,D-Pen5]enkephalin), kappa1 (U50,488H) or kappa3 (naloxone benzoylhydrazone) analgesia. In dose-response studies, 3-methoxynaltrexone (2.5 ng, i.c.v.) significantly shifted the ED50 values for heroin and its active metabolite, 6-acetylmorphine, without affecting the morphine curve. These results indicate that 3-methoxynaltrexone selectively blocks a novel 3H-M6G binding site which is responsible for the analgesic actions of heroin and M6G. This ability to selectively antagonize heroin actions opens new possibilities in the development of therapeutics for the treatment of opioid abuse.

Antisense mapping DOR-1 in mice: further support for delta receptor subtypes

In contrast to the pharmacological studies implicating delta-opioid receptor subtypes, cloning studies have identified only a single cDNA encoding a delta receptor, DOR-1. Antisense studies have established the importance of DOR-1 in delta analgesia in mice. Antisense mapping extends this approach to include oligodeoxynucleotides which are targeted against each of the exons of the gene. Five different antisense oligodeoxynucleotides based upon the three DOR-1 exons all block both spinal and supraspinal analgesic actions of the delta2 ligand [D-Ala2,Glu4]deltorphin, consistent with the suggestion that DOR-1 encodes the delta2 receptor. At the spinal level, [D-Pen2,D-Pen5]enkephalin (DPDPE) acts also acts through delta2 receptors and all the antisense probes block spinal DPDPE analgesia. However, supraspinally only the two antisense probes targeting exon 3 block DPDPE analgesia. The remaining three antisense probes based upon exons 1 and 2 are inactive. Thus, the delta receptors responsible for spinal and supraspinal DPDPE analgesia can be discriminated at the molecular level by antisense mapping.

Antisense mapping of MOR-1 in rats: distinguishing between morphine and morphine-6beta-glucuronide antinociception

In an effort to correlate the recently cloned MOR-1 receptor with the pharmacological actions of morphine and morphine-6beta-glucuronide (M6G), we have used an antisense paradigm. Rats were injected intracerebroventricularly (i.c.v.) with antisense oligodeoxynucleotides on days 1, 3 and 5 and tested for analgesia on day 6 after administration of morphine or M6G i.c.v. or after microinjection of morphine directly into either the periaqueductal gray or the locus coeruleus. When given i.c.v., the antisense oligodeoxynucleotide targeting the 5'-untranslated region of exon 1 significantly decreased the analgesic actions of morphine administered i.c.v. or microinjected directly into the periaqueductal gray or locus coeruleus, with the most profound inhibition occurring in the periaqueductal gray. Thus, antisense oligodeoxynucleotides administered into the lateral ventricle can diffuse into the brainstem and interfere with morphine actions. A mismatch antisense oligodeoxynucleotide with the same base composition in which the sequence of four bases was changed was inactive. This same exon 1 antisense oligodeoxynucleotide, which was active against morphine analgesia, failed to block M6G analgesia. In contrast, antisense sequences from exons 2 and 3 decreased M6G, and not morphine, analgesia. The antisense oligodeoxynucleotide against exon 4 slightly decreased both morphine and M6G antinociception. These results confirm the antisense mapping studies on exons 1, 2 and 3 of MOR-1 in mice, which implied the presence of a novel mu receptor subtype responsible for M6G analgesia that may represent a splice variant of MOR-1. Unlike in mice, the probe against exon 4 had a small effect on M6G analgesia.

Different central opioid receptor subtype antagonists modify maltose dextrin and deprivation-induced water intake in sham feeding and sham drinking rats

Different central opioid receptor subtypes participate in the mediation of intakes of simple (sucrose: mu, kappa 1) and complex (maltose dextrin: mu) carbohydrates as well as deprivation-induced water intake (mu) under real-feeding and real-drinking conditions. An identical pattern of mu and kappa 1 mediation of sucrose intake was observed in sham-feeding rats as well, suggesting their actions on orosensory mechanisms supporting sucose intake. The present study examined whether centrally administered general (naltrexone: 1-50 micrograms), mu (beta-funaltrexamine: 1-20 micrograms), mu 1 (naloxonazine: 50 micrograms), kappa 1 (nor-binaltorphamine: 1-20 micrograms), delta 1 ([D-Ala2, Leu5, Cys6]-enkephalin: 10-40 micrograms) or delta 2 (naltrindole isothiocyanate: 20 micrograms) opioid subtype antagonists altered either maltose dextrin (10%) intake during sham feeding or deprivation (24 h)-induced water intake during sham drinking in rats with gastric fistulas. Sham feeding significantly increased maltose dextrin intake (180%) and sham drinking significantly increased deprivation-induced water intake (256%) over a 60 min time course. Naltrexone significantly and dose-dependently reduced maltose dextrin intake (78%) in sham feeding rats, and deprivation-induced water intake (51%) in sham drinking rats. Maltose dextrin intake in sham feeding rats was significantly reduced by either kappa 1 (69%) or delta 1 (59%) opioid antagonism, was significantly increased by mu 1 antagonism (43%), and was not significantly affected by either mu or delta 2 opioid antagonism. Deprivation-induced water intake in sham drinking rats was significantly reduced by either mu (41%), mu 1 (28%), delta 1 (48%) or delta 2 (28%) opioid antagonism, but was not significantly affected by kappa 1 opioid antagonism. The difference in opioid receptor subtype mediation of maltose dextrin intake in real feeding and sham feeding conditions suggest that kappa 1 and delta 1 receptors are involved in the orosensory mechanisms supporting maltose dextrin intake, while mu receptors are involved in the ingestive and post-ingestive mechanisms supporting maltose dextrin intake. The different patterns of opioid involvement in sucrose and maltose dextrin intake in sham feeding and real feeding conditions provide further support for the hypothesis that at least two different carbohydrate taste systems exist. The difference in opioid receptor subtype mediation of deprivation-induced water intake in real drinking and sham drinking conditions may reflect the removal in the sham drinking condition of a mu-mediated prerestorative satiety mechanism, and the unmasking of other opioid-mediated signalling mechanisms.

A method to estimate in vivo D2 receptor occupancy by antipsychotic drugs

A computational method is presented to estimate in vivo receptor occupancies of frequently used antipsychotic medications, which may provide a way to determine their central nervous system (CNS) effects in humans. The method can be used to estimate occupancies of several receptor types based on the daily dose of antipsychotic medication. Estimates of D2 receptor occupancy by haloperidol based on this equation were compared with those yielded by positron emission tomography (PET) measures in humans for the same compounds and dosages: the results of this comparison validated the approach.

Novel receptor mechanisms for heroin and morphine-6 beta-glucuronide analgesia

The rapid metabolism of heroin to 6-acetylmorphine and its slower conversion to morphine has led many to believe that heroin and morphine act through the same receptors and that the differences between them are due to their pharmacokinetics. We now present evidence strongly implying that heroin and two potent mu drugs, fentanyl and etonitazine, act through a unique receptor mechanism similar to morphine-6 beta-glucuronide which is readily distinguished from morphine. Heroin, 6-acetylmorphine and morphine-6 beta-glucuronide show no analgesic cross tolerance to morphine in a daily administration paradigm, implying distinct receptors. Strains also reveal analgesic differences among the drugs. CXBK mice, which are insensitive to morphine, retain their analgesic sensitivity to heroin, 6-acetylmorphine, morphine-6 beta-glucuronide, fentanyl and etonitazine. Antisense mapping of the mu opioid receptor MOR-1 reveals that oligodeoxynucleotide probes against exon 2, which are inactive against morphine analgesia, block morphine-6 beta-glucuronide, heroin, fentanyl and etonitazine analgesia. Finally, an antisense probe targeting Gi alpha 1 blocks both heroin and morphine-6 beta-glucuronide, but not morphine, analgesia. These results indicate that heroin, 6-acetylmorphine, fentanyl and etonitazine all can produce analgesia through a novel mu analgesic system which is similar to that activated by morphine-6 beta-glucuronide.

Naloxone sensitive orphanin FQ-induced analgesia in mice

Orphanin FQ, also known as nociceptin, is a heptadecapeptide with very high affinity for a novel member of the cloned opioid receptor family which produces hyperalgesia in mice. In addition to hyperalgesia, which is observed soon after administration of orphanin FQ, we now describe a delayed analgesic response. Unlike orphanin FQ-induced hyperalgesia, orphanin FQ-induced analgesia is readily reversed by the opioid antagonist naloxone, implying an opioid mechanism of action. In view of the very poor affinity of orphanin FQ for all the known traditional opioid receptors and the low affinity of opioids for the 125I[Tyr14]orphanin FQ binding site, orphanin FQ-induced analgesia is probably mediated through a novel orphanin FQ receptor subtype.

Reductions in locomotor activity following central opioid receptor subtype antagonists in rats

Opioid agonists produce biphasic (decreases then increases) effects upon activity in rats. General opioid antagonists typically suppress activity. Selective opioid antagonists reduce weight and food intake. However, the latter effects cannot fully account for the former effects. To assess the possibility that selective opioid antagonists might decrease weight by increasing activity, the present study examined whether central administration of either mu (beta-funaltrexamine: 20 micrograms), mu1 (naloxonazine: 50 micrograms), delta1 ([D-Ala2,Leu5,Cys6]enkephalin: 40 micrograms), delta2 (naltrindole isothiocyanate: 20 micrograms), or kappa1 (nor-binaltorphamine: 20 micrograms) opioid antagonists altered total, ambulatory, or stereotypic activity. Each of the antagonists significantly reduced total (mu: 18%, mu1: 31%, delta1: 42%, delta2: 37%, kappa1: 31%), ambulatory (mu: 17%, mu1: 27%, delta1: 34%, delta2: 37%, kappa1: 31%), and stereotypic (mu: 19%, mu1: 34%, delta1: 49%, delta2: 37%, kappa1: 31%) activity on the first day. All three activity measures were reduced by delta1 and delta2 antagonism on the second day, whereas mu antagonism reduced total and stereotypic activity on the second day. The activity reductions induced by selective opioid receptor subtype antagonists parallel effects induced by general opioid antagonism, and suggest that antagonist-induced weight loss effects independent of intake reductions are not due to antagonist-induced hyperactivity.

Antisense oligodeoxynucleotides against the MOR-1 clone alter weight and ingestive responses in rats

MOR-1 encodes a mu receptor. In an effort to establish the relationship of this cloned opioid receptor with ingestive behavior and analgesia in rats, the present study examined the actions of four antisense oligodeoxynucleotides aimed at exons 1 (AS1), 2 (AS2), 3 (AS3) and 4 (AS4) of the MOR-1 clone, as well as a mismatch antisense sequence (MS1). Rats were administered intracerebroventricular injections (10 micrograms/2 microliters) of each of the oligodeoxynucleotides on days 1, 3 and 5. Body weight and spontaneous food and water intake were monitored daily. In addition, 2-deoxy-D-glucose (2DG)-induced hyperphagia, central Angiotensin II (ANG-II) induced hyperdipsia and central morphine analgesia were examined 24 h following the last antisense injection. AS1, AS2, AS3 and AS4 each significantly reduced body weight (7-17 g), food intake (8-13 g) and water intake (11-23 ml), while the vehicle or MS1 conditions significantly increased weight (9-20 g) and produced smaller reductions (2-4 g) in food intake. None of the AS probes altered the magnitude of either 2DG-induced hyperphagia or ANG-II-induced hyperdipsia. Central morphine analgesia was reduced by pretreatment with AS1 and AS4, but not AS2, AS3 or MS1. The sensitivity of general feeding to all four exons suggest that the receptor responsible for this action is encoded by the MOR-1 clone. The differences between feeding and morphine analgesia raise the possibility that these two actions are mediated through different mu receptor subtypes. Our results also demonstrate the viability of the in vivo antisense technique in modulating opioid-mediated ingestive responses.

Clinical assessment of the 1987 American College of Rheumatology criteria for rheumatoid arthritis

The 1987 American College of Rheumatology (ACR) criteria for the classification of rheumatoid arthritis (RA) were clinically assessed. These criteria do not include findings of synovial fluid (SF) analysis and require no exclusion criteria. We have studied sequential patients with arthritis seen in four rheumatology centers in the Philadelphia area. Classifications by the ACR criteria were compared with our clinical diagnoses. Two hundred ninety eight patients were evaluated, 113 with RA and 185 with other diagnoses. Classifications as RA by the ACR criteria corresponded to our clinical diagnosis in 95% of the cases, corroborating the high sensitivity previously reported. However, we found a lower specificity (73%) than that reported (89%). False positive classifications as RA were found in 71% of patients with psoriatic arthritis, 48% of patients with SLE, and 31% of patients with gout. The specificity could be improved to 89% by excluding disorders with obvious distinguishing extraarticular features such as psoriasis or by SF findings of monosodium urate crystals. Awareness of these possible sources of confusion will further increase the teaching and epidemiologic value of these useful simplified criteria.

Selective actions of central mu and kappa opioid antagonists upon sucrose intake in sham-fed rats

Intake of a palatable sucrose solution in real-fed rats is mediated in part by central mu and kappa opioid receptors. Since general opioid antagonists still inhibit sucrose intake in sham-fed rats, the present study examined whether centrally administered mu (beta-funaltrexamine: 5, 20 micrograms), mu1 (naloxonazine: 50 micrograms), kappa (nor-binaltorphamine: 1, 5, 20 micrograms), delta (naltrindole: 20 micrograms) or delta 1 (DALCE: 40 micrograms) opioid subtype antagonists altered sucrose intake in sham-fed rats in a similar manner to systemic naltrexone (0.01-1 mg/kg) and whether such effects were equivalent to altering the sucrose concentration. Sucrose (20%) intake in sham-fed rats was significantly and dose-dependently reduced by naltrexone (59%), beta-funaltrexamine (44%) and nor-binaltorphamine (62%), but not by naloxonazine, naltrindole or DALCE. The reductions in sham sucrose (20%) intake by general, mu and kappa antagonism were similar in pattern and magnitude to diluting sucrose concentration from 20% to 10% in untreated sham-fed rats. Since both real-fed and sham-fed rats share similar patterns of specificity of opioid effects, magnitudes and potencies of inhibition, it suggests that central mu and kappa antagonism acts on orosensory mechanisms supporting sucrose intake.

Reductions in body weight following chronic central opioid receptor subtype antagonists during development of dietary obesity in rats

Acute administration of long-acting general opioid antagonists reduces body weight and food intake in rats. In contrast, chronic administration of short-acting general opioid antagonists produces transient effects. The present study evaluated whether chronic central administration of selective long-acting antagonists of mu (beta-funaltrexamine, BFNA, 20 micrograms), mu1 (naloxonazine, 50 micrograms), delta1 ([D-Ala2,Leu5,Cys6]-enkephalin, DALCE, 40 micrograms), delta2 (naltrindole isothiocyanate, NTII, 20 micrograms) or kappa (nor-binaltorphamine, NBNI, 20 micrograms) opioid receptor subtypes altered weight and intake of rats exposed to a palatable diet of pellets, fat, milk and water, relative to pellet-fed and diet-fed controls. Diet-fed rats receiving chronic vehicle injections significantly increased weight (7-10%) and intake over the 11-day time course. Weight was significantly reduced over the time course in rats administered either BFNA (9%), naloxonazine (12%), DALCE (7%) or NTII (6%). Initial weight reductions failed to persist following chronic NBNI. All antagonists chronically reduced fat intake, but did not systematically alter total intake, pellet intake or milk intake relative to the pattern of weight loss. These data indicate that central mu, mu1, delta1, delta2, and, to a lesser degree, kappa receptors mediate long-term opioid modulation of weight even in animals maintained on diets that ultimately result in dietary obesity.

Hepatitis C infection, cryoglobulinemia, and vasculitic neuropathy. Treatment with interferon alfa: case report and literature review

A patient with mononeuropathy multiplex, hepatitis C viral infection, and mixed cryoglobulinemia had axonal degeneration by EMG and vasculitis of the epineurial vessels on sural nerve biopsy. There was no evidence of viral particles in the nerve by immunofluorescence. Treatment with interferon alfa improved the patient's symptoms and cleared the hepatitis C viral RNA and cryoglobulins from the serum.