RESUMEN
BACKGROUND: Patients with Crohn's disease (CD) may experience disease relapse on maintenance infliximab. Anti-drug antibodies likely contribute to loss of response, and serum infliximab levels likely correlate with efficacy. AIM: To prospectively evaluate the relationship between trough serum infliximab concentration and disease activity. METHODS: Adult patients (N = 327) with a diagnosis of CD who had received at least five consecutive infliximab infusions and who planned to receive at least two additional infusions were enrolled. The Crohn's Disease Activity Index (CDAI), serum infliximab, C-reactive protein (CRP) and antibodies-to-infliximab (ATI) were assessed at baseline, week 4 and week 8. Receiver operating characteristic (ROC) analysis examined the relationship between infliximab concentrations and disease activity. RESULTS: The mean CDAI score, which decreased 1.05 points between infusions, did not correlate with the mean change in trough infliximab concentration (+0.39 µg/mL; r = 0.099, P = 0.083), but was associated with the mean change in CRP concentration (r = 0.19, P < 0.001). Trough infliximab concentrations below 2.8-4.6 µg/mL best predicted a ≥ 70 point increase in the CDAI between infusions, and those below 2.7-2.8 µg/mL best predicted CRP >5 mg/mL at the second infusion. ATI at either visit decreased the proportion of patients with therapeutic infliximab trough levels compared with patients who were ATI negative (17.5% vs. 77.3% at visit 1 and 13.8% vs. 75.6% at visit 3; P < 0.001 for both comparisons). CONCLUSIONS: This prospective study confirms the relationship between trough infliximab concentrations, inflammation and antibodies-to-infliximab. Infliximab trough concentrations below 3 µg/mL may increase the likelihood of symptoms and inflammation (ClinicalTrials.gov identifier: NCT00676988).
Asunto(s)
Anticuerpos Monoclonales/sangre , Proteína C-Reactiva/metabolismo , Enfermedad de Crohn/tratamiento farmacológico , Fármacos Gastrointestinales/sangre , Adulto , Anticuerpos Monoclonales/uso terapéutico , Estudios de Cohortes , Enfermedad de Crohn/fisiopatología , Femenino , Fármacos Gastrointestinales/uso terapéutico , Humanos , Infliximab , Masculino , Persona de Mediana Edad , Estudios Prospectivos , Curva ROC , Índice de Severidad de la Enfermedad , Resultado del TratamientoRESUMEN
PET scanners require routine monitoring and quality control (QC) to ensure proper scanner performance. QC helps to ensure that PET equipment performs as specified by the manufacturer and that there have not been significant changes in the system response since acceptance. In this work we describe the maintenance history and we report on the results obtained from the PET system QC testing program over 5 years at two centers, both utilizing a Siemens Biograph 16 HiRez PET/CT system. QC testing programs were based on international standards and included the manufacturer's daily QC, monthly uniformity and sensitivity, quarterly cross-calibration and annual resolution and image quality. For the Winnipeg and Novara sites, two and one PET detector blocks have been replaced, respectively. Neither system has had other significant PET system related hardware replacements. The manufacturer's suggested daily QC was sensitive to detecting problems in the function of PET detector elements. The same test was not sensitive for detecting long term drifts in the systems: the Novara system observed a significant deterioration over five years of testing in the sensitivity which exhibited a decrease of 16% as compared to its initial value measured at system installation. The measure of the energy spectrum, showed that the 511 keV photopeak had shifted to a position of 468 keV. This shift was corrected by having service personnel perform a complete system calibration and detector block setup. We recommend including tests of system energy response and of sensitivity as part of a QC program since they can provide useful information on the actual performance of the scanner. A modification of the daily QC test by the manufacturer is suggested to monitor the long term stability of the system. Image quality and spatial resolution tests have proven to be of limited value for monitoring the system over time.
Asunto(s)
Imagenología Tridimensional/instrumentación , Imagenología Tridimensional/normas , Tomografía de Emisión de Positrones/instrumentación , Tomografía de Emisión de Positrones/normas , Irradiación Corporal Total/instrumentación , Irradiación Corporal Total/normas , Calibración , Documentación , Agencias Internacionales/normas , Control de Calidad , Conteo por Cintilación , Sensibilidad y EspecificidadRESUMEN
This study was initiated to characterize the metabolism and pharmacokinetics of SNC80 in rats and to evaluate the impact of Freund's complete adjuvant (FCA)-induced inflammation on its body disposition. In vitro, the disappearance and intrinsic clearance (CL(int)) of SNC80 were measured following incubations in recombinant rat CYPs and in phenotyped liver microsomes from naive and 24-h FCA-treated rats. The unbound fraction (f(u)) was assessed by ultrafiltration. Based on the Clint values, in vivo blood clearance of 3.35 and 2.48 L/h/kg were predicted in naive and FCA-treated rats. In vivo, SNC80 was administered to naive and 24-h FCA-treated rats at 10 micromol/kg i.v. and 50 micromol/kg p.o. The naive animals showed high plasma clearance (3.1 L/h/kg), low renal clearance (<0.02 L/h/kg) and poor bioavailability (<4%). Following i.v. administration, plasma clearance was lower (22%) in FCA-treated vs. untreated rats. Despite the decreases in f(u) (approximately 30%) and CL(int) (approximately 40%) in vitro, in vivo the apparent bioavailability and oral clearance were not significantly different between FCA-treated and naive rats. Hepatic and possibly intestinal losses contribute to the low bioavailability of SNC80. Non-hepatic mechanisms may compensate for the decrease in plasma clearance found in FCA-treated rats, preventing an increase in the oral bioavailability of SNC80.
Asunto(s)
Benzamidas/metabolismo , Benzamidas/farmacocinética , Modelos Animales de Enfermedad , Adyuvante de Freund/farmacología , Dolor/patología , Piperazinas/metabolismo , Piperazinas/farmacocinética , Receptores Opioides delta/agonistas , Animales , Benzamidas/química , Benzamidas/orina , Disponibilidad Biológica , Proteínas Sanguíneas , Sistema Enzimático del Citocromo P-450/metabolismo , Glicoproteínas/sangre , Humanos , Inflamación/patología , Masculino , Microsomas Hepáticos/efectos de los fármacos , Microsomas Hepáticos/enzimología , Orosomucoide , Piperazinas/química , Piperazinas/orina , Unión Proteica/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Proteínas Recombinantes/metabolismo , SolucionesRESUMEN
1. The aim was to identify the cytochrome P450 (CYP) enzymes responsible for the N-demethylation of morphine in vitro. 2. In human liver microsomes, normorphine formation followed Michaelis-Menten kinetics with mean Km and Vmax of 12.4 +/- 2.2 mM and 1546 +/- 121 pmol min(-1) mg(-1), respectively. In microsomes from a panel of 14 human livers phenotyped for 10 CYP enzymes, morphine N-demethylation correlated with testosterone 6beta-hydroxylation (r=0.91, p<0.001) and paclitaxel 6-alpha hydroxylation (r=0.72, p<0.001), two specific markers of CYP3A4 and CYP2C8, respectively. Normorphine formation decreased when incubated in the presence of troleandomycin or quercetin (by 46 and 33-36%, respectively), which further corroborates the contribution of CYP3A4 and CYP2C8. 3. Among eight recombinant human CYP enzymes tested, CYP3A4 and CYP2C8 exhibited the highest intrinsic clearance. More than 90% of morphine N-demethylation could be accounted for via the action of both CYP3A4 and CYP2C8. 4. The in vitro findings suggest that hepatic CYP3A4, and to a lesser extent CYP2C8, play an important role in the metabolism of morphine into normorphine.
Asunto(s)
Hidrocarburo de Aril Hidroxilasas/metabolismo , Sistema Enzimático del Citocromo P-450/metabolismo , Microsomas Hepáticos/enzimología , Morfina/metabolismo , Animales , Línea Celular , Citocromo P-450 CYP2C8 , Citocromo P-450 CYP3A , ADN Complementario , Humanos , Hidroxilación , Insectos , Metilación , Microsomas Hepáticos/metabolismo , Estructura Molecular , Derivados de la Morfina/análisis , Derivados de la Morfina/metabolismoRESUMEN
PURPOSE: This study assessed the influence of mdr1a P-glycoprotein (P-gp) gene disruption, gender and concentration on initial brain uptake clearance (Clup) of morphine, quinidine and verapamil. METHODS: Clup of radiolabeled substrates was determined in P-gp-competent and deficient [mdr1a(-/-)] mice by in situ brain perfusion. Brain:plasma distribution of substrates after i.v. administration was determined in both strains. RESULTS: Genetic disruption of mdr1a P-gp resulted in 1.3-, 6.6- and 14-fold increases in Clup for morphine, verapamil and quinidine, respectively. With the exception of small differences for verapamil, gender did not affect Clup. Saturable transport of verapamil and quinidine was observed only in P-gp-competent mice, with apparent IC50 values for efflux of 8.6 +/- 2.3 microM and 36 +/- 2 microM, respectively. Verapamil Clup was approximately 50% higher in mdr1a(+/-) vs. mdr1a(+/+) mice; no such difference was observed for quinidine. In P-gp-competent mice, uptake of verapamil and quinidine was unaffected by organic vehicles. Plasma decreased VER Clup to a greater extent in the presence of P-gp. The influence of P-gp in situ was lower than, but correlated with, the effect in vivo. CONCLUSIONS: P-gp decreases Clup of morphine, verapamil and quinidine in situ with little or no influence of gender, but this effect cannot fully account for the effects of P-gp in vivo. P-gp is the only saturable transport mechanism for verapamil and quinidine at the murine blood-brain barrier. The influence of protein binding on Clup may be enhanced by P-gp-mediated efflux.
Asunto(s)
Subfamilia B de Transportador de Casetes de Unión a ATP/genética , Subfamilia B de Transportador de Casetes de Unión a ATP/farmacocinética , Transportadoras de Casetes de Unión a ATP/genética , Transportadoras de Casetes de Unión a ATP/farmacocinética , Encéfalo/metabolismo , Caracteres Sexuales , Subfamilia B de Transportador de Casetes de Unión a ATP/deficiencia , Animales , Antimaláricos/sangre , Antimaláricos/farmacocinética , Barrera Hematoencefálica/genética , Bloqueadores de los Canales de Calcio/sangre , Bloqueadores de los Canales de Calcio/farmacocinética , Relación Dosis-Respuesta a Droga , Femenino , Masculino , Ratones , Ratones Noqueados , Morfina/sangre , Morfina/farmacocinética , Narcóticos/sangre , Narcóticos/farmacocinética , Perfusión/métodos , Quinidina/sangre , Quinidina/farmacocinética , Especificidad por Sustrato/genética , Verapamilo/sangre , Verapamilo/farmacocinéticaRESUMEN
OBJECTIVE: "Errorless compliance training" is a recently developed, success-based approach for teaching children to comply with parental requests without the use of coercive consequences. Two mothers were trained to use this intervention to reduce severe child defiance that was precipitating mother/child confrontations and physical abuse. METHOD: To determine probability of child compliance to specific requests, we observed mothers delivering requests to their child. We then developed a hierarchy of compliance probabilities for each child. Mothers were trained to deliver a high density of Level 1 requests (those that typically yielded compliance), and provide praise for child compliance. Lower probability request levels were introduced gradually, at a slow enough pace to preclude noncompliant responses, reducing the need for mothers to respond aversively to child behavior. RESULTS: At treatment completion and follow-up, both children demonstrated substantial improvements in compliance. CONCLUSIONS: The errorless approach may be well suited to managing parenting deficits and child opposition commonly associated with family violence.
Asunto(s)
Maltrato a los Niños/prevención & control , Trastornos de la Conducta Infantil/prevención & control , Crianza del Niño/psicología , Conducta Cooperativa , Relaciones Madre-Hijo , Madres/educación , Refuerzo Social , Adulto , Manejo de Caso , Niño , Preescolar , Femenino , Humanos , Masculino , Madres/psicología , Evaluación de Programas y Proyectos de Salud , RecompensaRESUMEN
Individuals with brain injury may experience severe cognitive and other impairments. For brain-injured parents, such deficits may be associated with child behavior problems, including noncompliance. We assessed the effects of a play period conducted by a brain-injured father on the compliance of his son, who had become uncooperative with his father after the injury. The child consistently demonstrated improved compliance during proximal and distal compliance sessions that followed father-son play periods.
Asunto(s)
Lesiones Encefálicas/psicología , Trastornos de la Conducta Infantil/terapia , Relaciones Padres-Hijo , Padres/psicología , Juego e Implementos de Juego , Niño , Trastornos de la Conducta Infantil/psicología , Humanos , Masculino , Persona de Mediana EdadRESUMEN
The authors employed staff training strategies designed to enhance generalization of teaching skills in staff working with persons with developmental disabilities. Staff training consultants initially employed a general case training approach involving the use of specially selected client program exemplars to provide three supervisory staff with generalized teaching skills. Subsequently, supervisory staff used the general case approach to train teaching skills to direct-care staff, with staff training support from the consultants (quasi-pyramidal training). Supervisors showed improvement in teaching skills after supervisory staff training, but only one of the three supervisors exceeded 70% correct skill use. After participating in the training of their own staff, however, supervisors demonstrated further improvements in skill use. All direct-care staff showed improvement after quasi-pyramidal training, with seven of the nine staff exceeding 70% correct skill use. General case quasi-pyramidal training appears to have potential as a strategy for promoting generalization of staff teaching skills in both trainees and trainers.
Asunto(s)
Terapia Conductista/educación , Generalización Psicológica , Capacitación en Servicio , Discapacidad Intelectual/rehabilitación , Grupo de Atención al Paciente , Actividades Cotidianas , Adolescente , Adulto , Niño , Curriculum , Femenino , Hogares para Grupos , Humanos , MasculinoRESUMEN
Persons sustaining a brain injury often exhibit aberrant response patterns and skill deficits that require remediation. To promote recovery, rehabilitation staff must be competent in use of therapeutic teaching and interaction skills. This study focused on teaching 13 direct-care rehabilitation therapists these skills in a multiple baseline design across skill dimensions. Performance-based approaches were used to promote acquisition of therapist skills, and the 'general case' strategy was used to enhance generalization. The general case approach involved use of multiple examples of teaching and interaction situations selected to sample the range of variability in the rehabilitation setting. Therapists were videotaped in simulations of various teaching and interaction situations before and after staff training. These observations were coded for correct use of teaching and interaction skills. Therapists demonstrated mean increases of approximately 30 percentage points in correct skill use after training. The present training format appears to provide an efficient strategy for training staff to promote rehabilitation efforts.
Asunto(s)
Lesiones Encefálicas/rehabilitación , Terapia Ocupacional/educación , Modalidades de Fisioterapia/educación , Adulto , Femenino , Humanos , Relaciones Interpersonales , Masculino , Persona de Mediana Edad , Competencia Profesional , Desarrollo de PersonalRESUMEN
P-glycoprotein (P-gp) and organic anion transporting polypeptides (Oatp) are expressed at the blood-brain barrier (BBB). There is little functional evidence for Oatp-mediated transport at the BBB. The peptidic delta opioid-receptor agonist [D-penicillamine(2,5)]-enkephalin (DPDPE) is a substrate of mdr1a P-gp and Oatp2. The present study evaluated the influence of these transporters on brain uptake of DPDPE by in situ perfusion in mice. Brain uptake was increased approximately 12-fold in mice lacking P-gp in the BBB, but the P-gp inhibitor dexverapamil did not increase uptake in P-gp-competent mice. In P-gp-deficient mice, DPDPE uptake was saturable (K(m) approximately 24 mM), and was inhibited by dexverapamil and the Oatp2 substrates digoxin, estradiol-17beta-glucuronide and fexofenadine. These results confirm P-gp-mediated efflux of DPDPE, and suggest functional uptake transport of DPDPE by Oatp, at the murine BBB.
Asunto(s)
Subfamilia B de Transportador de Casetes de Unión a ATP/genética , Transportadoras de Casetes de Unión a ATP/genética , Analgésicos Opioides/farmacocinética , Barrera Hematoencefálica/fisiología , Encefalina D-Penicilamina (2,5)/farmacocinética , Receptores Opioides delta/metabolismo , Terfenadina/análogos & derivados , Animales , Proteínas de Transporte de Anión , Barrera Hematoencefálica/efectos de los fármacos , Bloqueadores de los Canales de Calcio/farmacología , Proteínas Portadoras/metabolismo , Digoxina/farmacología , Inhibidores Enzimáticos/farmacología , Estradiol/análogos & derivados , Estradiol/farmacología , Antagonistas de los Receptores Histamínicos H1/farmacología , Masculino , Ratones , Ratones Noqueados , Perfusión , Receptores Opioides delta/agonistas , Terfenadina/farmacología , Verapamilo/farmacologíaAsunto(s)
Fibrinolíticos/uso terapéutico , Accidente Cerebrovascular/tratamiento farmacológico , Activador de Tejido Plasminógeno/uso terapéutico , Enfermedad Aguda , Aspirina/uso terapéutico , Bases de Datos Factuales , Toma de Decisiones , Medicina Basada en la Evidencia , Humanos , Ensayos Clínicos Controlados Aleatorios como Asunto , Accidente Cerebrovascular/prevención & controlRESUMEN
OBJECTIVE: Acute upper gastrointestinal (UGI) hemorrhage is a common, often serious condition encountered in the emergency department (ED). Previous research has suggested that transfusion of blood products may interfere with the hypercoagulable state induced by significant blood loss. Our objective was to determine whether the frequency of rebleeding is higher in patients with UGI bleeding who have received early blood transfusion. METHODS: The study was a retrospective chart review of patients admitted to hospital through the ED with a diagnosis of UGI hemorrhage. Inclusion criteria limited analysis to patients presenting with hematemesis, melena, or bloody nasogastric aspirate, in whom a UGI lesion was confirmed endoscopically during admission. RESULTS: A total of 214 charts were analyzed. Baseline demographic characteristics were similar in transfused and non-transfused patients. Presenting hemoglobin level was lower in the transfused group (86.5 v. 119.2 g/L, p < 0.001). Recurrent bleeding occurred in 99 (46%) patients and was more common in transfused patients (67 [66%] v. 33 [29%], p < 0.001). Logistic regression analysis revealed that transfusion and presenting hemoglobin level were the only variables with a statistically significant independent association with bleeding recurrence (p < 0.001 and p < 0.05 respectively). CONCLUSIONS: Our results support previous research suggesting that transfused UGI bleed patients have a higher rate of rebleeding. However, because of the retrospective design, causality cannot be inferred.
RESUMEN
Nonpeptide delta opioid agonists are analgesics with a potentially improved side-effect and abuse liability profile, compared to classical opioids. Andrews analysis of the NIH nonpeptide lead SNC-80 suggested the removal of substituents not predicted to contribute to binding. This approach led to a simplified lead, N, N-diethyl-4-[phenyl(1-piperazinyl)methyl]benzamide (1), which retained potent binding affinity and selectivity to the human delta receptor (IC(50) = 11 nM, mu/delta = 740, kappa/delta > 900) and potency as a full agonist (EC(50) = 36 nM) but had a markedly reduced molecular weight, only one chiral center, and increased in vitro metabolic stability. From this lead, the key pharmacophore groups for delta receptor affinity and activation were more clearly defined by SAR and mutagenesis studies. Further structural modifications on the basis of 1 confirmed the importance of the N, N-diethylbenzamide group and the piperazine lower basic nitrogen for delta binding, in agreement with mutagenesis data. A number of piperazine N-alkyl substituents were tolerated. In contrast, modifications of the phenyl group led to the discovery of a series of diarylmethylpiperazines exemplified by N, N-diethyl-4-[1-piperazinyl(8-quinolinyl)methyl]benzamide (56) which had an improved in vitro binding profile (IC(50) = 0.5 nM, mu/delta = 1239, EC(50) = 3.6 nM) and increased in vitro metabolic stability compared to SNC-80.
Asunto(s)
Benzamidas/síntesis química , Piperazinas/síntesis química , Quinolinas/síntesis química , Receptores Opioides delta/agonistas , Animales , Benzamidas/química , Benzamidas/metabolismo , Disponibilidad Biológica , Línea Celular , Cromatografía Líquida de Alta Presión , Humanos , Técnicas In Vitro , Espectrometría de Masas , Microsomas Hepáticos/metabolismo , Piperazinas/química , Piperazinas/metabolismo , Quinolinas/química , Quinolinas/metabolismo , Ensayo de Unión Radioligante , Ratas , Receptores Opioides delta/metabolismo , Receptores Opioides kappa/metabolismo , Receptores Opioides mu/metabolismo , Estereoisomerismo , Relación Estructura-Actividad , Termodinámica , TransfecciónRESUMEN
The design, synthesis, and pharmacological evaluation of a novel class of delta opioid receptor agonists, N, N-diethyl-4-(phenylpiperidin-4-ylidenemethyl)benzamide (6a) and its analogues, are described. These compounds, formally derived from SNC-80 (2) by replacing the piperazine ring with a piperidine ring containing an exocyclic carbon carbon double bond, were found to bind with high affinity and exhibit excellent selectivity for the delta opioid receptor as full agonists. 6a, the simplest structure in the class, exhibited an IC(50) = 0.87 nM for the delta opioid receptors and extremely high selectivity over the mu receptors (mu/delta = 4370) and the kappa receptors (kappa/delta = 8590). Rat liver microsome studies on a selected number of compounds show these olefinic piperidine compounds (6) to be considerably more stable than SNC-80. This novel series of compounds appear to interact with delta opioid receptors in a similar way to SNC-80 since they demonstrate similar SAR. Two general approaches have been established for the synthesis of these compounds, based on dehydration of benzhydryl alcohols (7) and Suzuki coupling reactions of vinyl bromide (8), and are herewith reported.
Asunto(s)
Benzamidas/síntesis química , Piperidinas/síntesis química , Receptores Opioides delta/agonistas , Administración Oral , Animales , Benzamidas/química , Benzamidas/metabolismo , Benzamidas/farmacología , Disponibilidad Biológica , Línea Celular , Cromatografía Líquida de Alta Presión , Humanos , Técnicas In Vitro , Espectrometría de Masas , Microsomas Hepáticos/metabolismo , Modelos Moleculares , Piperazinas/metabolismo , Piperidinas/química , Piperidinas/metabolismo , Piperidinas/farmacología , Ensayo de Unión Radioligante , Ratas , Receptores Opioides delta/metabolismo , Receptores Opioides kappa/metabolismo , Receptores Opioides mu/metabolismo , Estereoisomerismo , Relación Estructura-Actividad , Termodinámica , TransfecciónRESUMEN
OBJECTIVES: Errorless compliance training is a success-based, noncoercive intervention for children with severe oppositional behavior. The strategy involves hierarchical introduction of more demanding parental requests at a gradual pace that greatly reduces noncompliance and obviates the need for constraining consequences (e.g., time-out). In this study, this approach was evaluated as a treatment for severe disciplinary problems in children from violent homes. METHOD: Participants were 15 children (aged 3-10 years) and their mothers. All participants had experienced long-term family violence. Using a multiple-baseline design, the authors trained parents in a group format and conducted observations of child compliance in the home throughout the intervention. RESULTS: Observations indicated improvements in generalized child compliance that were maintained up to 6 months posttreatment. Pre-/post maternal reports indicated significant reductions in maternal perception of child noncompliance, externalizing and internalizing problems, and parenting stress. CONCLUSIONS: Researchers have noted a dearth of empirically supported interventions for children from violent homes. Errorless compliance training may help to fill this void, as it appears well suited to treatment of difficulties encountered by these youngsters and their parents.
Asunto(s)
Déficit de la Atención y Trastornos de Conducta Disruptiva/terapia , Hijo de Padres Discapacitados/psicología , Violencia Doméstica/psicología , Madres/educación , Psicoterapia de Grupo/métodos , Adulto , Déficit de la Atención y Trastornos de Conducta Disruptiva/psicología , Niño , Preescolar , Femenino , Humanos , Control Interno-Externo , Masculino , Relaciones Madre-Hijo , Resultado del TratamientoRESUMEN
The effects of the delta agonists SNC80 and deltorphin II on ambulation and rearing activity were measured in habituated and non-habituated rats. SNC80 (30, 100, 200, 400 nmol, i.c.v.) and deltorphin II (3, 15, 30, 60 nmol, i.c.v.) induced similar, dose-dependent biphasic locomotor effects in non-habituated subjects. An initial decrease in exploratory activity was associated with anxiogenic signs such as pilo-erection, freezing behaviour and pupil dilation for each drug. Pre-treatment with the delta antagonist naltrindole (10 nmol, i.c.v.) inhibited the depressant effect, but not the subsequent stimulant effect, on locomotor activity in response to 30 nmol deltorphin II in this assay (P<0.05). In habituated rats, deltorphin II (0.03, 0.1, 0.3, 3 nmol, i.c.v.) caused significant, naltrindole-reversible increases in locomotor activity (P<0.05 for all doses) at 1,000-fold lower doses than those required for a similar response to SNC80 (10, 30, 100, 300 nmol, i.c.v.). Pharmacokinetic studies suggest that these compounds penetrate the brain to similar extents following i.c.v. injection. The substantial potency difference between deltorphin II and SNC80 in stimulating locomotor activity in habituated rats suggests pharmacological heterogeneity for these delta opioid receptor agonists.