A Niclosamide-releasing hot-melt extruded catheter prevents Staphylococcus aureus experimental biomaterial-associated infection.

Biomaterial-associated infections are a major healthcare challenge as they are responsible for high disease burden in critically ill patients. In this study, we have developed drug-eluting antibacterial catheters to prevent catheter-related infections. Niclosamide (NIC), originally an antiparasitic drug, was incorporated into the polymeric matrix of thermoplastic polyurethane (TPU) via solvent casting, and catheters were fabricated using hot-melt extrusion technology. The mechanical and physicochemical properties of TPU polymers loaded with NIC were studied. NIC was released in a sustained manner from the catheters and exhibited in vitro antibacterial activity against Staphylococcus aureus and Staphylococcus epidermidis. Moreover, the antibacterial efficacy of NIC-loaded catheters was validated in an in vivo biomaterial-associated infection model using a methicillin-susceptible and methicillin-resistant strain of S. aureus. The released NIC from the produced catheters reduced bacterial colonization of the catheter as well as of the surrounding tissue. In summary, the NIC-releasing hot-melt extruded catheters prevented implant colonization and reduced the bacterial colonization of peri-catheter tissue by methicillin sensitive as well as resistant S. aureus in a biomaterial-associated infection mouse model and has good prospects for preclinical development.

The NK1 receptor antagonist aprepitant attenuates NK1 agonist-induced scratching behaviour in the gerbil after intra-dermal, topical or oral administration.

Experiments were conducted to develop a model to study the effect of oral and topical administration of the NK1 receptor antagonist aprepitant, on scratching behaviour in gerbils. The gerbil was selected due to its relevance for human NK1 receptor pharmacology. Intradermal injection of a specific NK1 receptor agonist GR73632 (100 nmol/100 µl) at the rostral back of gerbils produced scratching of the injection site. This could be attenuated by intradermal co-administration of a selective NK1 receptor antagonist aprepitant (30-100-300 nmol), demonstrating the role of dermal NK1 receptor in elicitation of scratching behaviour. Likewise, scratching was attenuated by oral (0.3-3-30 mg/kg) or topical application (0.01-0.1-1% w/v) of aprepitant and pharmacokinetic analysis of aprepitant levels in brain, blood and skin supported that efficacy of topically applied aprepitant was due to dermal rather than central target engagement. In conclusion, we showed that NK1 agonist-induced scratching in the gerbil can be reversed by systemic and topical administration of aprepitant. This test system may provide a useful model for the in vivo assessment of putative antipruritic agents.

Role of orexin-1 receptor mechanisms on compulsive food consumption in a model of binge eating in female rats.

Orexins (OX) and their receptors (OXR) modulate feeding, arousal, stress, and drug abuse. Neural systems that motivate and reinforce drug abuse may also underlie compulsive food seeking and intake. Therefore, the effects of GSK1059865 (5-bromo-N-[(2S,5S)-1-(3-fluoro-2-methoxybenzoyl)-5-methylpiperidin-2-yl]methyl-pyridin-2-amine), a selective OX(1)R antagonist, JNJ-10397049 (N-(2,4-dibromophenyl)-N'-[(4S,5S)-2,2-dimethyl-4-phenyl-1,3-dioxan-5-yl]urea), a selective OX(2)R antagonist, and SB-649868 (N-[((2S)-1-{[5-(4-fluorophenyl)-2-methyl-1,3-thiazol-4-yl]carbonyl}-2-piperidinyl)methyl]-1-benzofuran-4-carboxamide), a dual OX(1)/OX(2)R antagonist were evaluated in a binge eating (BE) model in female rats. BE of highly palatable food (HPF) was evoked by three cycles of food restriction followed by stress, elicited by exposing rats to HPF, but preventing them from having access to it for 15 min. Pharmacokinetic assessments of all compounds were obtained under the same experimental conditions used for the behavioral experiments. Topiramate was used as the reference compound as it selectively blocks BE in rats and humans. Dose-related thresholds for sleep-inducing effects of the OXR antagonists were measured using polysomnography in parallel experiments. SB-649868 and GSK1059865, but not JNJ-10397049, selectively reduced BE for HPF without affecting standard food pellet intake, at doses that did not induce sleep. These results indicate, for the first time, a major role of OX(1)R mechanisms in BE, suggesting that selective antagonism at OX(1)R could represent a novel pharmacological treatment for BE and possibly other eating disorders with a compulsive component.

GSK1614343, a novel ghrelin receptor antagonist, produces an unexpected increase of food intake and body weight in rodents and dogs.

Ghrelin is a 28-amino-acid polypeptide expressed in the stomach and hypothalamus that stimulates GH secretion, increases food intake (FI) and promotes body weight (BW) gain most likely via activation of the growth hormone secretagogue receptor type 1a (GHSR1a). GSK1614343 is a novel selective and potent GHSR antagonist with no partial agonist properties, recently characterized as GH secretion inhibitor by Sabbatini et al. [Chem Med Chem 2010;5:1450-1455]. In the present study, GSK1614343 (10 mg/kg) was not able to antagonize ghrelin-induced food consumption in rat, but unexpectedly stimulated FI and BW gain in both rats and dogs, a profile associated with decreased ghrelin plasma level. Interestingly, GSK1614343 selectively reduced the pro-opiomelanocortin mRNA levels in rat hypothalami chronically treated with the compound. To better understand the observed effects, we administered GSK1614343 (30 mg/kg) to Ghsr null mice and measured body mass components (fat, lean and free fluid) by using a NMR spectrometer. The increases of FI and BW were abolished in Ghsr null mice, while fat and lean masses increased in wild-type mice. Taken together, these results indicate that the orexigenic effect of GSK1614343 is mediated by GHSR1a and that the weight gain could be attributed to the increase of both adiposity and muscle mass, but not to fluid retention. The observed dissociation between effects on GH secretion and effects on FI/BW is inconsistent with a simple hormone-receptor model, suggesting unknown underlying regulations of the ghrelin system whose understanding require further investigation.

In vitro and in vivo characterization of the novel GABAB receptor positive allosteric modulator, 2-{1-[2-(4-chlorophenyl)-5-methylpyrazolo[1,5-a]pyrimidin-7-yl]-2-piperidinyl}ethanol (CMPPE).

There is preclinical evidence supporting the finding that the GABA(B) receptor orthosteric agonist, baclofen, has significant effects on eating behavior suggesting the potential therapeutic application of this compound for the treatment of eating related disorders. However, the wide clinical use of baclofen might be limited by the appearance of sedative and motor impairment effects. The identification of positive allosteric modulators (PAMs) of GABA(B) receptors represents a novel therapeutic approach to reduce the centrally-mediated adverse effects typical of the GABA(B) receptor orthosteric agonist. In the present work, we report the in vitro profile of a novel chemical structure, 2-{1-[2-(4-chlorophenyl)-5-methylpyrazolo[1,5-a]pyrimidin-7-yl]-2-piperidinyl}ethanol (CMPPE) identified by screening the GSK compound collection. CMPPE potentiates GABA-stimulated [(35)S]GTPγS binding to membranes of human recombinant cell line and of rat brain cortex. GABA concentration-response curves (CRC) in the presence of fixed concentrations of CMPPE, in rat native tissue, revealed an increase of both the potency and maximal efficacy of GABA. A similar modulatory effect was observed in GABA(B) receptor-mediated activation of inwardly rectifying potassium channels in hippocampal neurons. CMPPE (30-100 mg/kg) and GS39783 (100 mg/kg) significantly decreased food consumption in rat without impairment on the animal locomotor activity. On the contrary, baclofen (2.5 mg/kg) decreased both food intake and motor performance. All together these findings confirm the role of GABA(B) system in controlling animal food intake and for the first time demonstrate that GABA(B) receptor PAMs may represent a novel pharmacological approach to treat eating disorders without unwanted sedative effects.

The selective phosphodiesterase 9 (PDE9) inhibitor PF-04447943 (6-[(3S,4S)-4-methyl-1-(pyrimidin-2-ylmethyl)pyrrolidin-3-yl]-1-(tetrahydro-2H-pyran-4-yl)-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-one) enhances synaptic plasticity and cognitive function in rodents.

Inhibition of phosphodiesterase 9 (PDE9) has been reported to enhance rodent cognitive function and may represent a potential novel approach to improving cognitive dysfunction in Alzheimer's disease. PF-04447943, (6-[(3S,4S)-4-methyl-1-(pyrimidin-2-ylmethyl)pyrrolidin-3-yl]-1-(tetrahydro-2H-pyran-4-yl)-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-one), a recently described PDE9 inhibitor, was found to have high affinity (Ki of 2.8, 4.5 and 18 nM) for human, rhesus and rat recombinant PDE9 respectively and high selectivity for PDE9 versus PDEs1-8 and 10-11. PF-04447943 significantly increased neurite outgrowth and synapse formation (as indicated by increased synapsin 1 expression) in cultured hippocampal neurons at low (30-100 nM) but not high (300-1000 nM) concentrations. PF-04447943 significantly facilitated hippocampal slice LTP evoked by a weak tetanic stimulus at a concentration of 100 nM but failed to affect response to the weak tetanus at either 30 or 300 nM, or the LTP produced by a theta burst stimulus. Systemic administration of PF-04447943 (1-30 mg/kg p.o.) dose-dependently increased cGMP in the cerebrospinal fluid 30 min after administration indicating target engagement in the CNS of rats. PF-04447943 (1-3 mg/kg p.o.) significantly improved cognitive performance in three rodent cognition assays (mouse Y maze spatial recognition memory model of natural forgetting, mouse social recognition memory model of natural forgetting and rat novel object recognition with a scopolamine deficit). When administered at a dose of 3 mg/kg p.o., which improved performance in novel object recognition, PF-04447943 significantly increased phosphorylated but not total GluR1 expression in rat hippocampal membranes. Collectively these data indicate that PF-04447943 is a potent, selective brain penetrant PDE9 inhibitor that increased indicators of hippocampal synaptic plasticity and improved cognitive function in a variety of cognition models in both rats and mice. Results with PF-04447943 are consistent with previously published findings using a structurally diverse PDE9 inhibitor, BAY73-6199, and further support the suggestion that PDE9 inhibition may represent a novel approach to the palliative remediation of cognitive dysfunction.

Cognitive and neural determinants of response strategy in the dual-solution plus-maze task.

Response strategy in the dual-solution plus maze is regarded as a form of stimulus-response learning. In this study, by using an outcome devaluation procedure, we show that it can be based on both action-outcome and stimulus-response habit learning, depending on the amount of training that the animals receive. Furthermore, we show that deactivation of the dorso-medial and the dorso-lateral striatum with Botulinum neurotoxin A, mimicked or abolished, respectively, the effects of practice on the sensitivity of the response strategy to outcome devaluation. These findings have relevant implications for the understanding of the learning mechanisms underlying different overt behaviors in this widely used maze task.

Adenoviral-mediated Cre expression effectively suppresses GlyT1 binding in the thalamic area of GlyT1 conditional knock-out mice.

To properly understand the function of genes of neurological interest, in vivo manipulation in the adult is essential, particularly when the target gene is involved in brain development. Moreover, since the physiological effects of target protein may be region-specific, targeting a distinct brain region could be required to dissect these effects in specific brain locations. Infection of somatic tissues of transgenic mice bearing loxP-flanked gene sequences with a viral vector expressing Cre recombinase provides a means of allowing flexible spatio-temporal control of target gene expression. Viral vector-mediated Cre expression could be used to mediate localized gene modulation in a specific brain region. In the present study this technology was applied to the glycine transporter type-1 (GlyT1) protein which is responsible for the uptake of synaptic glycine in the forebrain and has been implicated as a therapeutic target for the treatment of schizophrenia. Since GlyT1 is widely expressed in glial cells, we employed an adenoviral-based vector (Ad5) to deliver Cre protein, due to the preferentially transduction of glial cells by adenoviral vectors in rodent brain. We show significant reduced GlyT1 binding specifically in the thalamic area of conditional GlyT1 (GlyT1c) transgenic mice injected with Ad5-Cre virus, as measured by GlyT1 autoradiography. In conclusion, we demonstrated the validity of viral vector-mediated delivery of Cre to loxP targeted transgenic mice as a novel strategy to investigate target gene function in selected subregions of the adult brain, which provides a valuable technique to investigate gene function both in normal physiology and in disease models.

Ventral striatal plasticity and spatial memory.

Spatial memory formation is a dynamic process requiring a series of cellular and molecular steps, such as gene expression and protein translation, leading to morphological changes that have been envisaged as the structural bases for the engram. Despite the role suggested for medial temporal lobe plasticity in spatial memory, recent behavioral observations implicate specific components of the striatal complex in spatial information processing. However, the potential occurrence of neural plasticity within this structure after spatial learning has never been investigated. In this study we demonstrate that blockade of cAMP response element binding protein-induced transcription or inhibition of protein synthesis or extracellular proteolytic activity in the ventral striatum impairs long-term spatial memory. These findings demonstrate that, in the ventral striatum, similarly to what happens in the hippocampus, several key molecular events crucial for the expression of neural plasticity are required in the early stages of spatial memory formation.

Selective PDE inhibitors rolipram and sildenafil improve object retrieval performance in adult cynomolgus macaques.

RATIONALE: Selective phosphodiesterase (PDE) inhibitors improve the formation of hippocampus-dependent memories in several rodent models of cognition. However, studies evaluating the effects of PDE inhibition on prefrontal cortex-dependent cognition and in monkeys are rare. OBJECTIVES: The present study investigates the effect of the PDE4 inhibitor rolipram and the PDE5 inhibitor sildenafil on object retrieval performance. Object retrieval is a prefrontal cortical-mediated task, which is likely to capture attention and response inhibition. MATERIALS AND METHODS: The ability to retrieve a food reward from a clear box with an open side positioned in various orientations was assessed in adult male cynomolgus monkeys (Macaca fascicularis). RESULTS: Rolipram (0.003-0.03 mg/kg, intramuscular [i.m.]) and sildenafil (0.3-3 mg/kg, i.m.) dose-dependently increased correct first reaches during difficult trials, reaching significance at 0.01 and 1 mg/kg, respectively. For both drugs, correct reaches were increased approximately 20%; that is, performance was improved from approximately 50 to approximately 70% correct. CONCLUSIONS: Both rolipram and sildenafil improved object retrieval performance, thus demonstrating the cognition-enhancing effects of PDE inhibition on a prefrontal task of executive function in monkeys.

Co-activation of glutamate and dopamine receptors within the nucleus accumbens is required for spatial memory consolidation in mice.

RATIONALE: The nucleus accumbens receives glutamatergic and dopaminergic inputs converging onto common dendrites. Recent behavioral data demonstrated that intra-accumbens administrations of either glutamate or dopamine (DA) antagonist impair spatial memory consolidation. Thus, also based on the biochemical and molecular findings demonstrating interactions among the different receptors subtypes for glutamate and dopamine, it is conceivable that memory consolidation within this structure might be modulated by glutamate-dopamine receptor interactions. OBJECTIVES: The purpose of this study was to examine the effects of intra-accumbens co-administrations of glutamate and DA antagonists on the consolidation of spatial information. METHODS: On day 1, CD1 male mice were placed in an open field containing five different objects and immediately after three sessions of habituation the animals were injected intra-accumbens with either vehicle or low doses of the N-methyl-D: -aspartate (NMDA; AP-5 50 ng/side), the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA; DNQX 5 ng/side), the D1 (SCH23390 12.5 ng/side) and the D2 (sulpiride 25 ng/side) antagonists that were ineffective alone in disrupting object displacement. Separate groups were then focally injected with a combination of one of the glutamate antagonists with one of the dopamine antagonists. Twenty-four hours later, the ability of mice to discriminate object displacement was assessed. RESULTS: Controls and mice injected with ineffective doses of the NMDA, the AMPA, the D1 or the D2 antagonists were always able to react to the object displacement. On the contrary, the groups administered with the different combinations (AP-5 and SCH23390, AP-5 and sulpiride, DNQX and SCH23390, DNQX and sulpiride) of glutamate and dopamine antagonists did not discriminate the spatial change. CONCLUSIONS: These results demonstrate that glutamate-dopamine receptor interactions within the accumbens are essential for the consolidation process of spatial information.

Distinct roles of the different ionotropic glutamate receptors within the nucleus accumbens in passive-avoidance learning and memory in mice.

Research on the role of the nucleus accumbens in behaviour has been largely focused on the functions of this structure in conditioning to appetitive stimuli. It has been suggested that a network comprising the nucleus accumbens and its convergent inputs might mediate dissociable functions in the acquisition, the consolidation and the retrieval of information. However, findings related to a role of this structure in aversive conditioning are somewhat contradictory, and its involvement in this form of learning is still under debate. Moreover, very little evidence is available on the step of information processing mediated by the accumbens. Thus the purpose of this study was to investigate the effects of the blockade of the AMPA and NMDA glutamate receptors, which have been suggested to mediate the transmission of information from the limbic system to this structure, on a classical aversive conditioning task - the one-trial step through inhibitory avoidance paradigm (24 h interval between training and testing). Intra-accumbens focal injections of AP-5 and DNQX (NMDA and AMPA antagonists, respectively) were performed immediately after training, before training and before testing in mice. The NMDA antagonist (37.5, 75 and 150 ng per side) impaired animal performance only if administered immediately after but not before training or before testing. Conversely, DNQX (0.5, 1.0 and 5.0 ng per side) reduced the step through latencies when administered before training and before testing. These findings suggest that NMDA receptor activation within the accumbens is necessary in formation but not expression of memory for inhibitory avoidance. AMPA receptors, instead, are necessary for the acquisition and the expression but not consolidation of inhibitory avoidance memory.

GR89,696: a potent kappa-opioid agonist with subtype selectivity in rhesus monkeys.

GR89,696 is a synthetic kappa-opioid receptor agonist, recently reported to have an agonist profile consistent with selectivity at the proposed "kappa(2)" subtype. The present studies evaluated the effects of GR89,696 in vitro (i.e., in radioligand binding and [(35)S]guanosine-5'-O-(3-thio)triphosphate assays) and in vivo in rhesus monkeys, in assays used to study kappa-opioid agonists (i.e., thermal antinociception, sedation and muscle relaxation, diuresis, and increases in serum prolactin levels, as well as ethylketocyclazocine and U69,593 discrimination). Furthermore, the sensitivity of GR89,696 to naltrexone and nor-binaltorphimine (nor-BNI) antagonism was compared with that of U50,488 and U69,593, ligands selective for the proposed "kappa(1)" subtype. Overall, GR89,696 displayed the profile of a highly potent kappa-opioid agonist, following parenteral administration in rhesus monkeys. GR89,696 was less sensitive than U50,488 and U69,593 to naltrexone or nor-BNI antagonism, consistent with an action through the proposed kappa(2) receptor subtype.

Induction and maintenance of ethanol self-administration in cynomolgus monkeys (Macaca fascicularis): long-term characterization of sex and individual differences.

BACKGROUND: Investigations of oral ethanol self-administration in nonhuman primates have revealed important parallels with human alcohol use and abuse, yet many fundamental questions concerning the individual risk to, and the biological basis of, excessive ethanol consumption remain unanswered. Moreover, many conditions of access to ethanol in nonhuman primate research are largely unexplored. This set of experiments extends within- and across-session exposure to ethanol to more fully characterize individual differences in oral ethanol self-administration. METHODS: Eight male and eight female adult cynomolgus monkeys (Macaca fascicularis) were exposed to daily oral ethanol self-administration sessions for approximately 9 months. During the first 3 months, a fixed-time (FT) schedule of food delivery was used to induce the consumption of an allotted dose of ethanol in 16-hr sessions. Subsequently, the FT schedule was suspended, and ethanol was available ad libitum for 6 months in 16- or 22-hr sessions. RESULTS: Cynomolgus monkeys varied greatly in their propensity to self-administer ethanol, with sex and individual differences apparent within 10 days of ethanol exposure. Over the last 3 months of ethanol access, individual average ethanol intakes ranged from 0.6 to 4.0 g/kg/day, resulting in blood ethanol concentrations from 5 to 235 mg/dl. Males drank approximately 1.5-fold more than females. In addition, heavy-, moderate-, and light-drinking phenotypes were identified by using daily ethanol intake and the percentage of daily calories obtained from ethanol as criteria. CONCLUSIONS: Cynomolgus monkeys displayed a wide intersubject range of oral ethanol self-administration with a procedure that used a uniform and prolonged induction that restricted early exposure to ethanol and subsequently allowed unlimited access to ethanol. There were sex and stable individual differences in the propensity of monkeys to consume ethanol, indicating that this species will be important in characterizing risk factors associated with heavy-drinking phenotypes.

Oral self-administration of ethanol, phencyclidine, methadone, pentobarbital and quinine in rhesus monkeys.

RATIONALE: Simultaneous and sequential drug use among clinical populations is the norm, whereas the pattern of self-administration of multiple drugs among non-human primate populations has not been thoroughly explored. OBJECTIVES: To determine the relationship between the preferences and intakes of a large group of rhesus monkeys exposed to various orally available solutions. METHODS: Thirteen male and eleven female young adult rhesus monkeys (Macaca mulatta) were exposed to orally available drug solutions using a concurrent choice (drug and water) procedure, where fluid delivery was made contingent upon single spout contacts (fixed ratio one). RESULTS: Ethanol (0.25-16% w:v) produced biphasic effects on the number of fluid deliveries obtained, with peak ethanol preferences over water demonstrated at the 1-2% w:v concentrations. No preferences for the N-methyl-d-aspartate receptor antagonist phencyclidine or water were demonstrated at lower concentrations (0. 0078125-0.125 mg/ml) and, at higher concentrations (0.25, 0.5 mg/ml), a preference for water was demonstrated. The mu opioid receptor agonist methadone (0.001-0.3 mg/ml) and the prototypic bitter substance quinine (0.001-0.3 mg/ml) failed to produce preferences for drug or water. A large preference for water over the barbiturate pentobarbital (0.01-3 mg/ml) was also demonstrated. After rank-ordering the subjects based on their drug preferences or intakes, modest to no correlations across drugs were demonstrated. CONCLUSIONS: These results reveal that a robust ethanol preference is not predictive of a preference for drugs of abuse from other classes and suggests that fluid intakes were correlated, irrespective of the presence or absence of drug in the solution.

Interactions between social stress and morphine in the periaqueductal gray: effects on affective vocal and reflexive pain responses in rats.

RATIONALE: Endogenous opioid systems within the mesencephalic periaqueductal gray matter (PAG) appear to be intricately involved in many affective, defensive, submissive, and reflexive responses, and these systems are activated by aversive stimuli. OBJECTIVES: The present experiments evaluated the influence of opioid receptors within the PAG on affective vocal and reflexive responses to aversive stimuli in socially inexperienced, as well as defensive and submissive responses in defeated, adult male Long-Evans rats. METHODS: Defeat stress consisted of: (1) an aggressive confrontation with a "resident" stimulus rat in which the experimental "intruder" rat exhibited escape, defensive and submissive behaviors [i.e. upright, supine postures and ultrasonic vocalizations (USV)], and subsequently, (2) protection from the resident rat with a wire mesh screen for ca. 25 min. Defeat stress was immediately followed by an experimental session with thermal antinociceptive and tactile startle stimuli (20 psi airpuffs). RESULTS: The mu opioid receptor agonist morphine (0.3, 1, 3 microgram IC) attenuated startle-induced USV and the tail-flick reflex in socially inexperienced and defeated rats, with both groups of rats demonstrating equal sensitivity to morphine. Morphine decreased defeat-induced USV and increased the display of the crouch posture in defeated rats; these morphine effects in socially inexperienced and defeated rats were re- versed with the opioid receptor antagonist naltrexone (0.1 mg/kg IP). CONCLUSIONS: These results reveal that the ventrolateral PAG is an important site in which mu opioid receptor agonists such as morphine mediate affective vocal and submissive responses, yet this structure is not critical in the display of defeat stress-augmented effects of morphine. Endogenous opioid mechanisms appear to participate in the organization of defensive behavior, namely, to facilitate a shift from active to passive forms of coping.

Oral ethanol self-administration in rhesus monkeys: behavioral and neurochemical correlates.

BACKGROUND: Previous research has revealed that orally administered ethanol serves as a reinforcer in nonhuman primates. The purposes of the present study were to examine the relationship between ethanol preferences and intakes in two distinct self-administration contexts and to reveal some of the behavioral and neurochemical correlates of oral ethanol self-administration in monkeys. METHODS: Three cohorts of 13 to 29 rhesus monkeys (Macaca mulatta) were socially housed and given daily, 1-hr, one-spout access to an ethanol solution (8.4%, w/v) sweetened with aspartame. Twelve of these monkeys were subsequently selected, individually housed, and given daily, 2-hr, two-spout access to a range of ethanol concentrations (0.25-16%, w/v) concurrently with water. RESULTS: These monkeys (National Institute on Alcohol Abuse and Alcoholism group) showed a marked preference for ethanol (0.5-4%, w/v) over water, and ethanol preferences were 3-fold greater than those of a second group of 12 monkeys (University of Michigan group) purchased from a commercial vendor. Ethanol consumption was consistent across the self-administration paradigms. Monkeys that consumed large quantities of ethanol under the one-spout, social-housing conditions continued to drink large quantities of ethanol under the two-spout, individual-housing conditions (r = 0.86). An association between ethanol preferences and intakes was also demonstrated. Monkeys with the greatest preferences for ethanol over water under the two-spout choice conditions consumed the largest quantities of ethanol (r = 0.82). Finally, cerebrospinal fluid 5-hydroxyindoleacetic acid concentrations were inversely related to ethanol preference but not to ethanol intake. CONCLUSIONS: These results indicate that ethanol consumption is stable across contexts and is positively correlated with the preference for ethanol over water.

kappa-Opioid receptor effects of butorphanol in rhesus monkeys.

Butorphanol and nalbuphine have substantial affinity for mu and kappa-opioid receptor sites, yet their behavioral effects in monkeys are largely consistent with a mu receptor mechanism of action. Using ethylketocyclazocine (EKC) discrimination and diuresis assays in rhesus monkeys (Macaca mulatta), the purpose of the current investigation was to characterize the in vivo kappa-opioid activity of these compounds through the use of an insurmountable mu-opioid receptor antagonist, clocinnamox. Alone, butorphanol (0.001-0.032 mg/kg i.m.) failed to generalize to EKC, and pretreatment with the competitive opioid receptor antagonist quadazocine (0.1 or 0.32 mg/kg i.m.) did not alter this generalization. At 24 h after clocinnamox (0.1 mg/kg i.m.) administration, butorphanol fully generalized to EKC, and this generalization was maintained in two of three monkeys at 72 h. Parallel results were observed in diuresis: butorphanol alone and in the presence of quadazocine (1 mg/kg i.m.) did not alter urine output, and a marked diuretic effect was demonstrated 24 h to 2 weeks after clocinnamox administration. Clocinnamox did not alter the discriminative stimulus or diuretic effects of nalbuphine or of the kappa-opioid receptor agonists EKC or U69593. These results are consistent with an in vivo agonist activity of butorphanol at kappa-opioid receptors that can only be demonstrated when an insurmountable antagonist has substantially eliminated the dominant receptor population through which it exerts its action.

Systemic effects of E-2078, a stabilized dynorphin A(1-8) analog, in rhesus monkeys.

RATIONALE: E-2078 ([N-methyl-Tyr1, N-methyl-Arg7, D-Leu8] dynorphin A(1-8) ethylamide) is a dynorphin A(1-8) analog with a reduced tendency to be biotransformed, when compared to the unmodified opioid peptide. E-2078 has been found to produce kappa-opioid agonist effects in vivo in rodents. OBJECTIVE: In the present studies, we investigated whether systemically administered E-2078 could produce kappa-agonist effects in rhesus monkeys, in tests of antinociception, diuresis and ethyl-ketocyclazocine (EKC) discrimination. METHODS: E-2078 (0.32-18 mg/kg, SC, IM or IV) was tested in the warm water (50 degrees, 55 degrees C) tail withdrawal assay of thermal antinociception. The diuretic effects of E-2078 (0.056-1.8 mg/kg, SC) were also compared to those of the kappa-agonist, U69,593 (0.01-0.32 mg/kg, SC). Lastly, the effects of E-2078 (0.1-3.2 mg/kg, SC or IV) were studied in rhesus monkeys trained to discriminate EKC (0.0056 mg/kg SC) from vehicle, in a food-reinforced operant procedure. RESULTS: E-2078 did not produce thermal antinociception in rhesus monkeys following SC or IM administration, up to the largest doses presently studied (i.e., 18 and 10 mg/kg, respectively). E-2078 caused thermal antinociception by the IV route, but this effect was not apparently mediated by kappa- or mu-opioid receptors, as shown by its insensitivity to quadazocine (1 mg/kg) pretreatment. However, SC E-2078 caused diuresis, and this effect was blocked by quadazocine pretreatment, consistent with mediation by kappa-opioid receptors. E-2078 generalized in EKC-discriminating monkeys, but only after the largest dose (3.2 mg/kg), and only following IV administration. CONCLUSIONS: The present studies suggest that systemically administered E-2078 can produce some kappa-receptor mediated effects in rhesus monkeys, but its profile of action is not identical to non-peptidic kappa-agonists following all routes of administration, or across all experimental situations.