Open-label study of etanercept treatment in patients with moderate-to-severe plaque psoriasis who lost a satisfactory response to adalimumab.

BACKGROUND: Some patients with plaque psoriasis experience secondary failure of tumour necrosis factor inhibitor therapy. OBJECTIVES: To evaluate efficacy, safety and patient-reported outcomes (PROs) with etanercept in patients with secondary adalimumab failure. METHODS: This phase IV open-label single-arm estimation study (NCT01543204) enrolled patients on adalimumab who had achieved static Physician's Global Assessment (sPGA) score 0/1 (clear/almost clear). Patients subsequently lost response, defined as sPGA ≥ 3 or loss of 50% improvement in Psoriasis Area and Severity Index (PASI 50). At baseline, patients had involved body surface area ≥ 10%, sPGA ≥ 3 and PASI ≥ 10. Antiadalimumab antibodies (ADAs) were measured at screening. Patients received etanercept 50 mg twice weekly for 12 weeks, followed by 50 mg weekly. The primary end point was sPGA 0/1 at week 12 (intention-to-treat analysis; no hypothesis tested). Additional outcomes included rates of sPGA 0/1, PASI responses, safety, PROs of itch, pain and flaking, Dermatology Life Quality Index, treatment satisfaction and Work Productivity and Activity Impairment questionnaire. RESULTS: Sixty-four patients enrolled; 67% had ADAs. sPGA 0/1 rates at week 12 were 39·7% [95% confidence interval (CI) 27·6-52·8; primary end point] and 45% (95% CI 29·3-61·5) for patients positive for ADAs and 35% (95% CI 15·4-59·2) for patients negative for ADAs. PASI 75 response rates at week 12 were 47·5% (95% CI 31·5-63·9) for patients who were positive for ADAs and 50% (95% CI 27·2-72·8) for patients negative for ADAs. No new safety signals were observed. PROs of itch, pain and flaking consistently improved at week 12 and were maintained through week 24. CONCLUSIONS: Patients with psoriasis who experienced secondary failure of adalimumab achieved satisfactory response to etanercept regardless of ADA status.

Examination of the Staphylococcus aureus nitric oxide reductase (saNOR) reveals its contribution to modulating intracellular NO levels and cellular respiration.

Staphylococcus aureus nitrosative stress resistance is due in part to flavohemoprotein (Hmp). Although hmp is present in all sequenced S. aureus genomes, 37% of analyzed strains also contain nor, encoding a predicted quinol-type nitric oxide (NO) reductase (saNOR). DAF-FM staining of NO-challenged wild-type, nor, hmp and nor hmp mutant biofilms suggested that Hmp may have a greater contribution to intracellular NO detoxification relative to saNOR. However, saNOR still had a significant impact on intracellular NO levels and complemented NO detoxification in a nor hmp mutant. When grown as NO-challenged static (low-oxygen) cultures, hmp and nor hmp mutants both experienced a delay in growth initiation, whereas the nor mutant's ability to initiate growth was comparable with the wild-type strain. However, saNOR contributed to cell respiration in this assay once growth had resumed, as determined by membrane potential and respiratory activity assays. Expression of nor was upregulated during low-oxygen growth and dependent on SrrAB, a two-component system that regulates expression of respiration and nitrosative stress resistance genes. High-level nor promoter activity was also detectable in a cell subpopulation near the biofilm substratum. These results suggest that saNOR contributes to NO-dependent respiration during nitrosative stress, possibly conferring an advantage to nor+ strains in vivo.

DAT isn't all that: cocaine reward and reinforcement require Toll-like receptor 4 signaling.

The initial reinforcing properties of drugs of abuse, such as cocaine, are largely attributed to their ability to activate the mesolimbic dopamine system. Resulting increases in extracellular dopamine in the nucleus accumbens (NAc) are traditionally thought to result from cocaine's ability to block dopamine transporters (DATs). Here we demonstrate that cocaine also interacts with the immunosurveillance receptor complex, Toll-like receptor 4 (TLR4), on microglial cells to initiate central innate immune signaling. Disruption of cocaine signaling at TLR4 suppresses cocaine-induced extracellular dopamine in the NAc, as well as cocaine conditioned place preference and cocaine self-administration. These results provide a novel understanding of the neurobiological mechanisms underlying cocaine reward/reinforcement that includes a critical role for central immune signaling, and offer a new target for medication development for cocaine abuse treatment.

Opioid activation of toll-like receptor 4 contributes to drug reinforcement.

Opioid action was thought to exert reinforcing effects solely via the initial agonism of opioid receptors. Here, we present evidence for an additional novel contributor to opioid reward: the innate immune pattern-recognition receptor, toll-like receptor 4 (TLR4), and its MyD88-dependent signaling. Blockade of TLR4/MD2 by administration of the nonopioid, unnatural isomer of naloxone, (+)-naloxone (rats), or two independent genetic knock-outs of MyD88-TLR4-dependent signaling (mice), suppressed opioid-induced conditioned place preference. (+)-Naloxone also reduced opioid (remifentanil) self-administration (rats), another commonly used behavioral measure of drug reward. Moreover, pharmacological blockade of morphine-TLR4/MD2 activity potently reduced morphine-induced elevations of extracellular dopamine in rat nucleus accumbens, a region critical for opioid reinforcement. Importantly, opioid-TLR4 actions are not a unidirectional influence on opioid pharmacodynamics, since TLR4(-/-) mice had reduced oxycodone-induced p38 and JNK phosphorylation, while displaying potentiated analgesia. Similar to our recent reports of morphine-TLR4/MD2 binding, here we provide a combination of in silico and biophysical data to support (+)-naloxone and remifentanil binding to TLR4/MD2. Collectively, these data indicate that the actions of opioids at classical opioid receptors, together with their newly identified TLR4/MD2 actions, affect the mesolimbic dopamine system that amplifies opioid-induced elevations in extracellular dopamine levels, therefore possibly explaining altered opioid reward behaviors. Thus, the discovery of TLR4/MD2 recognition of opioids as foreign xenobiotic substances adds to the existing hypothesized neuronal reinforcement mechanisms, identifies a new drug target in TLR4/MD2 for the treatment of addictions, and provides further evidence supporting a role for central proinflammatory immune signaling in drug reward.

The neuropharmacology of prolactin secretion elicited by 3,4-methylenedioxymethamphetamine ("ecstasy"): a concurrent microdialysis and plasma analysis study.

3,4-methylenedioxymethamphetamine (MDMA) is a substituted phenethylamine that is widely abused as the street drug "ecstasy". Racemic MDMA (S,R(+/-)-MDMA) and its stereoisomers elicit complex spectrums of psychobiological, neurochemical, and hormonal effects. In this regard, recent findings demonstrated that S,R(+/-)-MDMA and its stereoisomer R(-)-MDMA elicit increases in striatal extracellular serotonin levels and plasma levels of the hormone prolactin in rhesus monkeys. In the present mechanistic study, we evaluated the role of the serotonin transporter and the 5-HT(2A) receptor in S,R(+/-)-MDMA- and R(-)-MDMA-elicited prolactin secretion in rhesus monkeys through concurrent microdialysis and plasma analysis determinations and drug interaction experiments. Concurrent neurochemical and hormone determinations showed a strong positive temporal correlation between serotonin release and prolactin secretion. Consistent with their distinct mechanisms of action and previous studies showing that the serotonin transporter inhibitor fluoxetine attenuates the behavioral and neurochemical effects of S,R(+/-)-MDMA, pretreatment with fluoxetine attenuated serotonin release elicited by either S,R(+/-)-MDMA or R(-)-MDMA. As hypothesized, at a dose that had no significant effects on circulating prolactin levels when administered alone, fluoxetine also attenuated prolactin secretion elicited by S,R(+/-)-MDMA. In contrast, combined pretreatment with both fluoxetine and the selective 5-HT(2A) receptor antagonist M100907 was required to attenuate prolactin secretion elicited by R(-)-MDMA, suggesting that this stereoisomer of S,R(+/-)-MDMA elicits prolactin secretion through both serotonin release and direct agonism of 5-HT(2A) receptors. Accordingly, these findings inform our understanding of the neuropharmacology of both S,R(+/-)-MDMA and R(-)-MDMA and the regulation of prolactin secretion.

Interaction of 5-HT2A and 5-HT2C receptors in R(-)-2,5-dimethoxy-4-iodoamphetamine-elicited head twitch behavior in mice.

Drug-elicited head-twitch behavior is a useful model for studying hallucinogen activity at 5-HT(2A) receptors in the mouse. Chemically diverse compounds active in this assay yield biphasic dose-effect curves, but there is no compelling explanation for the "descending" portion of these functions. A set of experiments was designed to test the hypothesis that the induction of head-twitch behavior is mediated by agonist actions at 5-HT(2A) receptors, whereas the inhibition of head-twitch behavior observed at higher doses results from competing agonist activity at 5-HT(2C) receptors. The effects of the phenethylamine hallucinogen R(-)-2,5-dimethoxy-4-iodoamphetamine (DOI) on head-twitch behavior were studied over a range of doses in the mouse, generating a characteristic biphasic dose-response curve. Pretreatment with the selective 5-HT(2A) antagonist (+)-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenylethyl)]-4-piperidine-methanol (M100907) shifted only the ascending limb of the DOI dose-effect function, whereas pretreatment with the nonselective 5-HT(2A/2C) antagonist 3-{2-[4-(4-fluorobenzoyl)piperidin-1-yl]ethyl}quinazoline-2,4(1H,3H)-dione (ketanserin) produced a parallel shift to the right in the DOI dose-response curve. Administration of the 5-HT(2C) agonist S-2-(chloro-5-fluoro-indol-l-yl)-1-methylethylamine (Ro 60-0175) noncompetitively inhibited DOI-elicited head-twitch behavior across the entire dose-effect function. Finally, pretreatment with the selective 5-HT(2C) antagonists 6-chloro-5-methyl-1-[(2-[2-methylpyrid-3-yloxy]pyrid-5yl)carbamoyl]indoline (SB242084) or 8-[5-(2,4-dimethoxy-5-(4-trifluoromethylphenylsulfonamido)phenyl-5-oxopentyl]-1,3,8-triazaspiro[4,5]decane-2,4-dione hydrochloride (RS 102221) did not alter DOI-elicited head-twitch behavior on the ascending limb of the dose-response curve but shifted the descending limb of the DOI dose-response function to the right. The results of these experiments provide strong evidence that DOI-elicited head-twitch behavior is a 5-HT(2A) agonist-mediated effect, with subsequent inhibition of head-twitch behavior being driven by competing 5-HT(2C) agonist activity.

Blockade of the serotonin 5-HT2A receptor suppresses cue-evoked reinstatement of cocaine-seeking behavior in a rat self-administration model.

The serotonin 5-HT2A receptor (5-HT-sub(2A)R) may play a role in reinstatement of drug-seeking. This study investigated the ability of a selective 5-HT-sub(2A)R antagonist to suppress reinstatement evoked by exposure to cues conditioned to cocaine self-administration. Cocaine self-administration (0.75 mg/kg/0.1 mL/6 s infusion; FR 4) was trained in naïve, free-fed rats to allow interpretation of results independent from changes related to food deprivation stress. Pretreatment with the selective 5-HT-sub(2A)R antagonist M100907 (volinanserin) failed to reduce rates of operant responding for cocaine infusions. On the other hand, M100907 (0.001-0.8 mg/kg ip) significantly suppressed the cue-induced reinstatement of cocaine-seeking behavior following extinction; effective M100907 doses did not alter operant responding for cues previously associated with sucrose self-administration. Importantly, a greater magnitude of active lever presses on the initial extinction session (high extinction responders) predicted the maximal susceptibility to M100907-induced suppression of cue-evoked reinstatement. The findings indicate that blockade of the 5-HT-sub(2A)R attenuates the incentive-motivational effects of cocaine-paired cues, particularly in high extinction responders, and suggests that M100907 may afford a therapeutic advance in suppression of cue-evoked craving and/or relapse.

Stereospecific and nonstereospecific effects of (+)- and (-)-morphine: evidence for a new class of receptors?

The unnatural (+) enantiomer of morphine had minimal activity in three opiate assays in vitro: the rat brain homogenate binding assay, the electrically stimulated guinea pig ileum assay, and the inhibition of adenylate cyclase in neuroblastoma X glioma hybrid cell homogenates. When (+)-morphine was microinfected into the periaqueductal gray (a site known to mediate morphine analgesia) of drug-naive rats, there was only minimal analgesia, but the hyperresponsivity usually observed after microinfection of (-)-morphine occurred. Also, when (+)-morphine was microinfected into the midbrain reticular formation of drug-naive rats, rotation similar to that following microinjection of (-)-morphine occurred. These behaviors were not blocked by naloxone. Significantly, they typically occur in precipitated abstinence in morphine-dependent rats. These observations suggest that there are at least two classes of receptors, one stereospecific and blocked by naloxone and the other only weakly stereospecific and not blocked by naloxone, and that precipitated abstinence may be due, in part, to a selective blockade of receptors of the former class but not of the latter.

Irreversible ligands with high selectivity toward delta and mu opiate receptors.

Alkylating agents that display strong selectivity for opiate receptor types delta or mu were prepared by appropriate modification of the structures of the strong analgesics fentanyl, etonitazene, and endoethenotetrahydrooripavine. The availability of these substances should facilitate studies of the structural basis of receptor specificity and of the physiologic roles of these receptors.

Synthesis, radiosynthesis and in vivo evaluation of [I]-4-(2-(bis(4-fluorophenyl)methoxy)ethyl)-1-(4-iodobenzyl)piperidine as a selective tracer for imaging the dopamine transporter.

Dopamine transporter (DAT) neuroimaging is a useful tool in Parkinson's disease diagnosis, staging and follow-up providing information on the integrity of the dopaminergic neurotransmitter system in vivo. 4-(2-(Bis(4-fluorophenyl)-methoxy)ethyl)-1-(4-iodobenzyl)piperidine (7) has nanomolar affinity for DAT and better selectivity over the other monoamine transporters compared with the existing SPECT radioligands for DAT. The aim of this study was to synthesize and evaluate [(123)I]-7 as an in vivo tracer for DAT.The tributylstannyl precursor was synthesized with an overall yield of 25%. [(123)I]-7 was synthesized by electrophilic destannylation with a yield of 40±10%. Radiochemical purity appeared to be >98%, whereas specific activity was at least 667 GBq/µmol. Biodistribution studies in mice showed brain uptake of 0.96±0.53%ID/g at 30 s post injection (p.i.) and 0.26±0.02%ID/g at 3 h p.i. High blood activity was observed at all time points. Pretreatment with Cyclosporin A raised brain uptake indicating that [(123)I]-7 is transported by P-glycoprotein (P-gp) pumps. In rats, regional brain distribution of [(123)I]-7 was not in agreement with DAT distribution. These results indicate that [(123)I]-7 is not suitable for mapping DAT in vivo but could be a useful tracer for the P-gp transporter.

The stimulus effects of 8-OH-DPAT: evidence for a 5-HT2A receptor-mediated component.

A previous investigation in our laboratory found that the stimulus effects of the 5-HT2A agonist, LSD, are potentiated by 5-HT1A receptor agonists including the prototypic agonist, 8-OH-DPAT. Also suggestive of behaviorally relevant interactions between 5-HT1A and 5-HT2A receptors are behavioral analyses of locomotor activity, head-twitch response, forepaw treading and production of the serotonin syndrome; in some instances effects are augmented, in other, diminished. These observations led us in the present investigation to test the hypothesis that stimulus control by 8-OH-DPAT [0.2 mg/kg; 15 min pretreatment time] is modulated by 5-HT2A ligands. Stimulus control was established with 8-OH-DPAT in a group of 10 rats. A two-lever, fixed ratio 10, positively reinforced task with saline controls was employed. As shown previously, stimulus control by 8-OH-DPAT and the generalization of 8-OH-DPAT to the 5-HT1A partial agonist, buspirone, was completely blocked by the selective 5-HT1A antagonist, WAY-100635. In contrast, antagonism by the selective 5-HT2A antagonist, M100907 [0.1 mg/kg; 30 min pretreatment time], of 8-OH-DPAT and of the generalization of 8-OH-DPAT to buspirone was statistically significant but less than complete. In light of our previous conclusions regarding the interactions of 5-HT1A agonists with LSD-induced stimulus control, the present data suggest that the interaction between 5-HT1A and 5-HT2A receptors is bidirectional in drug discrimination studies.

Subtype-selective corticotropin-releasing factor receptor agonists exert contrasting, but not opposite, effects on anxiety-related behavior in rats.

The corticotropin-releasing factor (CRF) system mediates stress responses. Extrahypothalamic CRF1 receptor activation has anxiogenic-like properties, but anxiety-related functions of CRF2 receptors remain unclear. The present study determined the effects of intracerebroventricular administration of a CRF2 agonist, urocortin 3, on behavior of male Wistar rats in the shock-probe, social interaction, and defensive withdrawal tests of anxiety-like behavior. Equimolar doses of stressin1-A, a novel CRF1 agonist, were administered to separate rats. The effects of pyrazolo[1,5-a]-1,3,5-triazin-4-amine,8-[4-(bromo)-2-chlorophenyl]-N, N-bis(2-methoxyethyl)-2,7-dimethyl-(9Cl) (MJL-1-109-2), a CRF1 antagonist, on behavior in the shock-probe test also were studied. Stressin1-A increased anxiety-like behavior in the social interaction and shock-probe tests. Stressin1-A elicited behavioral activation and defensive burying at lower doses (0.04 nmol), but it increased freezing, grooming, and mounting at 25-fold higher (1-nmol) doses. Conversely, systemic administration of MJL-1-109-2 (10 mg/kg) had anxiolytic-like effects in the shock-probe test. Unlike stressin1-A or MJL-1-109-2, i.c.v. urocortin 3 infusion did not alter anxiety-like behavior in the shock-probe test across a range of doses that reduced locomotion and rearing and increased grooming. Urocortin 3 also did not decrease social interaction, but it decreased anxiety-like behavior in the defensive withdrawal test at a 2-nmol dose. Thus, i.c.v. administration of CRF1 and CRF2 agonists produced differential, but not opposite, effects on anxiety-like behavior. Urocortin 3 (i.c.v.) did not consistently decrease or increase anxiety-like behavior, the latter unlike effects seen previously after local microinjection of CRF2 agonists into the septum or raphe. With increasing CRF1 activation, however, the behavioral expression of anxiety qualitatively changes from "coping" to "noncoping" and offensive, agonistic behaviors.

Psilocybin-induced stimulus control in the rat.

Although psilocybin has been trained in the rat as a discriminative stimulus, little is known of the pharmacological receptors essential for stimulus control. In the present investigation rats were trained with psilocybin and tests were then conducted employing a series of other hallucinogens and presumed antagonists. An intermediate degree of antagonism of psilocybin was observed following treatment with the 5-HT(2A) receptor antagonist, M100907. In contrast, no significant antagonism was observed following treatment with the 5-HT(1A/7) receptor antagonist, WAY-100635, or the DA D(2) antagonist, remoxipride. Psilocybin generalized fully to DOM, LSD, psilocin, and, in the presence of WAY-100635, DMT while partial generalization was seen to 2C-T-7 and mescaline. LSD and MDMA partially generalized to psilocybin and these effects were completely blocked by M-100907; no generalization of PCP to psilocybin was seen. The present data suggest that psilocybin induces a compound stimulus in which activity at the 5-HT(2A) receptor plays a prominent but incomplete role. In addition, psilocybin differs from closely related hallucinogens such as 5-MeO-DMT in that agonism at 5-HT(1A) receptors appears to play no role in psilocybin-induced stimulus control.

Intermittent Access to Ethanol Induces Escalated Alcohol Consumption in Primates.

BACKGROUND: Escalation of voluntary alcohol drinking is characteristic of alcohol addiction and can be induced in rodents using intermittent access to alcohol. This model has been used to evaluate candidate therapeutics, but key systems involved in the transition into alcohol addiction, such as CRF, differ in their organization between rodents and primates. We examined the ability of an intermittent access schedule to induce escalation of voluntary alcohol drinking in non-human primates and used this model to assess the role of corticotropin releasing hormone (CRF) signaling in this process. METHODS: Four young adult male rhesus macaques were given access to an 8.4% alcohol solution every other weekday (EOD; M, W, F), while four other young adult males were given the same solution every weekday (ED; M-F). Subjects were then administered a CRF1 antagonist, antalarmin. RESULTS: EOD increased alcohol intake by up to 50% over baseline, with a more pronounced increase immediately following reintroduction of alcohol. For the morning/daytime sessions, EOD subjects increased their consumption by 83% over baseline. Differences between ED and EOD schedules emerged quickly, and EOD-induced escalation resulted in pharmacologically active BAC's. EOD-induced alcohol consumption was insensitive to CRFR1 blockade by antalarmin, but subjects with high CSF levels of CRF were more responsive. CONCLUSIONS: Similar to what has been observed in rodents, intermittent access results in an escalation of voluntary alcohol drinking in non-human primates. In contrast to findings in rats, recruitment of the CRF system does not seem to be involved in the escalated alcohol drinking observed under these conditions, though individual differences in CRF system activity may play a role.

Potential uses of corticotropin-releasing hormone antagonists.

Corticotropin-releasing hormone (CRH), its natural homologs urocortins (UCN) 1, 2, and 3, and several types of CRH receptors (R), coordinate the behavioral, endocrine, autonomic, and immune responses to stress. The potential use of CRH antagonists is currently under intense investigation. Selective antagonists have been used experimentally to clarify the role of CRH-related peptides in anxiety and depression, addictive behavior, inflammatory disorders, acute and chronic neurodegeneration, and sleep disorders, as well as preterm labor.

Hallucinogen-like actions of 5-methoxy-N,N-diisopropyltryptamine in mice and rats.

Few studies have examined the effects of 5-methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT) in vivo. In these studies, 5-MeO-DIPT was tested in a drug-elicited head twitch assay in mice where it was compared to the structurally similar hallucinogen N,N-dimethyltryptamine (N,N-DMT) and challenged with the selective serotonin (5-HT)2A antagonist M100907, and in a lysergic acid diethylamide (LSD) discrimination assay in rats where its subjective effects were challenged with M100907 or the 5-HT 1A selective antagonist WAY-100635. Finally, the affinity of 5-MeO-DIPT for three distinct 5-HT receptors was determined in rat brain. 5-MeO-DIPT, but not N,N-DMT, induced the head twitch responses in the mouse, and this effect was potently antagonized by prior administration of M100907. In rats trained with LSD as a discriminative stimulus, there was an intermediate degree (75%) of generalization to 5-MeO-DIPT and a dose-dependent suppression of response rates. These interoceptive effects were abolished by M100907, but were not significantly attenuated by WAY-100635. Finally, 5-MeO-DIPT had micromolar affinity for 5-HT 2A and 5-HT 2C receptors, but much higher affinity for 5-HT 1A receptors. 5-MeO-DIPT is thus effective in two rodent models of 5-HT2 agonist activity, and has affinity at receptors relevant to hallucinogen effects. The effectiveness with which M100907 antagonizes the behavioral actions of this compound, coupled with the lack of significant antagonist effects of WAY-100635, strongly suggests that the 5-HT 2A receptor is an important site of action for 5-MeO-DIPT, despite its apparent in vitro selectivity for the 5-HT 1A receptor.

Pharmacological characterization of the opioid inactive isomers (+)-naltrexone and (+)-naloxone as antagonists of toll-like receptor 4.

BACKGROUND AND PURPOSE: The toll-like receptor TLR4 is involved in neuropathic pain and in drug reward and reinforcement. The opioid inactive isomers (+)-naltrexone and (+)-naloxone act as TLR4 antagonists, reversing neuropathic pain and reducing opioid and cocaine reward and reinforcement. However, how these agents modulate TLR4 signalling is not clear. Here, we have elucidated the molecular mechanism of (+)-naltrexone and (+)-naloxone on TLR4 signalling. EXPERIMENTAL APPROACH: BV-2 mouse microglial cell line, primary rat microglia and primary rat peritoneal macrophages were treated with LPS and TLR4 signalling inhibitors. Effects were measured using Western blotting, luciferase reporter assays, fluorescence microscopy and ELISA KEY RESULTS: (+)-Naltrexone and (+)-naloxone were equi-potent inhibitors of the LPS-induced TLR4 downstream signalling and induction of the pro-inflammatory factors NO and TNF-α. Similarly, (+)-naltrexone or (+)-naloxone inhibited production of reactive oxygen species and increased microglial phagocytosis, induced by LPS. However, (+)-naltrexone and (+)-naloxone did not directly inhibit the increased production of IL-1ß, induced by LPS. The drug interaction of (+)-naloxone and (+)-naltrexone was additive. (+)-Naltrexone or (+)-naloxone inhibited LPS-induced activation of IFN regulatory factor 3 and production of IFN-ß. However, they did not inhibit TLR4 signalling via the activation of either NF-κB, p38 or JNK in these cellular models. CONCLUSIONS AND IMPLICATIONS: (+)-Naltrexone and (+)-naloxone were TRIF-IFN regulatory factor 3 axis-biased TLR4 antagonists. They blocked TLR4 downstream signalling leading to NO, TNF-α and reactive oxygen species. This pattern may explain, at least in part, the in vivo therapeutic effects of (+)-naltrexone and (+)-naloxone.

Serotonergic/glutamatergic interactions: potentiation of phencyclidine-induced stimulus control by citalopram.

Previous investigations in our laboratory have found that the stimulus effects of the hallucinogenic serotonergic agonists DOM and LSD are potentiated by phencyclidine [PCP], a non-competitive NMDA antagonist. Also suggestive of behaviorally significant serotonergic/glutamatergic interactions is our finding that stimulus control by both PCP and LSD is partially antagonized by the mGlu2/3 agonist, LY 379268. These observations coupled with the fact that the stimulus effects of LSD and DOM are potentiated by selective serotonin reuptake inhibitors [SSRIs] led us in the present investigation to test the hypothesis that stimulus control by PCP is potentiated by the SSRI, citalopram. Stimulus control was established with PCP [3.0 mg/kg; 30 min pretreatment time] in a group of 12 rats. A two-lever, fixed ratio 10, positively reinforced task with saline controls was employed. Potentiation by citalopram of an intermediate dose of PCP was observed. In an attempt to establish the mechanism by which citalopram might interact with PCP, subsequent experiments examined the effects on that interaction of antagonists at serotonergic receptors. It was found that the selective 5-HT2C-selective antagonists, SDZ SER 082 and SB 242084, significantly, albeit only partially, blocked the effects of citalopram on PCP. In agreement with our previous conclusions regarding the interaction of citalopram with DOM, the present data suggest that potentiation of the stimulus effects of PCP by citalopram are mediated in part by agonist activity at 5-HT2C receptors.

The stimulus properties of LSD in C57BL/6 mice.

RATIONALE: Drug-induced stimulus control has proven to be a powerful tool for the assessment of a wide range of psychoactive drugs. Although a variety of species has been employed, the majority of studies have been in the rat. However, with the development of techniques which permit the genetic modification of mice, the latter species has taken on new importance. Lysergic acid diethylamide [LSD], the prototypic indoleamine hallucinogen, has not previously been trained as a discriminative stimulus in mice. OBJECTIVE: To demonstrate the feasibility of LSD-induced stimulus control in the mouse and to provide a preliminary characterization of the stimulus properties of LSD in that species. METHODS: Male C57BL/6 mice were trained using a left or right nose-poke operant on a fixed ratio 10, water reinforced task following the injection of lysergic acid diethylamide [LSD, 0.17 or 0.30 mg/kg, s.c.; 15 min pretreatment] or vehicle. RESULTS: Stimulus control was established in 6 of 16 mice at a dose of LSD of 0.17 mg/kg after 39 sessions. An increase in dose to 0.30 mg/kg for the remaining mice resulted in stimulus control in an additional 5 subjects. In the low dose group, subsequent experiments demonstrated an orderly dose-effect relationship for LSD and a rapid offset of drug action with an absence of LSD effects 60 min after injection. When LSD [0.17 mg/kg] was administered in combination with the selective 5-HT2A antagonist, M100907, LSD-appropriate responding was significantly but incompletely reduced to approximately 50%; concurrently, response rates declined significantly. In mice trained with a dose of LSD of 0.30 mg/kg, full generalization to the phenethylamine hallucinogen, [-]-2,5-dimethoxy-4-methylamphetamine [DOM] was observed. CONCLUSIONS: The present data demonstrate the feasibility of LSD-induced stimulus control in the mouse. The general features of stimulus control by LSD in the mouse closely resemble those observed in the rat but the present data suggest that there may be significant differences as well.

Neurokinin-1 receptor antagonism attenuates neuronal activity triggered by stress-induced reinstatement of alcohol seeking.

Substance P (SP) and its cognate neurokinin-1 receptor (NK1R) are involved in alcohol-related behaviors. We have previously reported that NK1R antagonism attenuates stress-induced reinstatement of alcohol seeking and suppresses escalated alcohol self-administration, but does not affect primary reinforcement or cue-induced reinstatement. Here, we administered an NK1R antagonist or vehicle prior to footshock-induced reinstatement of alcohol seeking, and mapped the resulting neuronal activation using Fos immunohistochemistry. As expected, vehicle treated animals exposed to footshock showed induction of Fos immunoreactivity in several regions of the brain stress circuitry, including the amygdala (AMG), nucleus accumbens (NAC), dorsal raphe nucleus (DR), prefrontal cortex (PFC), and bed nucleus of the stria terminalis (BNST). NK1R antagonism selectively suppressed the stress-induced increase in Fos in the DR and NAC shell. In the DR, Fos-induction by stress largely overlapped with tryptophan hydroxylase (TrpH), indicating activation of serotonergic neurons. Of NAC shell neurons activated during stress-induced reinstatement of alcohol seeking, about 30% co-expressed dynorphin (DYN), while 70% co-expressed enkephalin (ENK). Few (<1%) activated NAC shell neurons coexpressed choline acetyltransferase (ChAT), which labels the cholinergic interneurons of this region. Infusion of the NK1R antagonist L822429 into the NAC shell blocked stress-induced reinstatement of alcohol seeking. In contrast, L822429 infusion into the DR had no effect, suggesting that the influence of NK1R signaling on neuronal activity in the DR is indirect. Taken together, our results outline a potential pathway through which endogenous NK1R activation mediates stress-induced alcohol seeking.