Effects of inter- and intra-observer variability on echocardiographic measurements in awake cats

The objective of this study was to determine intra- and inter-observer variability of echocardiographic measurements in awake cats. Four observers with different levels of experience in echocardiography performed 96 echocardiographic examinations in four cats on four different days over a 3-week period. The examinations were randomized and blinded. The maximum within-day and between-day CV values were 17.4 and 18.5% for inter-ventricular septal thickness in diastole, 18.7 and 22.6% for left ventricular free-wall thickness in diastole, 9.8 and 14.9% for left ventricular end-diastolic diameter, 20.8 and 15.2% for left ventricular end-systolic diameter, and 21.2 and 18.4% for left ventricular shortening fraction. The maximum within-day CV values were most often associated with the least competent observer (i.e. the graduate student) and, the minimum CV values with the most competent observer (i.e. the associate professor in cardiology). A significant interaction between cat and observer was also evidenced. Thus, the most competent observer could not be replaced by any of the other observers.

The origin and processes of mud volcanism: new insights from Trinidad

The mobilized sediments expelled by the mud volcanoes in Trinidad correspond to liquefied argillaceous and sandy material in which the solid fraction is systematically polygenic and originating from several formations (Cretaceous to Pliocene). The mud is notably rich in thingrained quartz that is angular and frequently mechanically damaged related to shearing at great depth, during the sedimentary burial, and/or hydraulic fracturing processes. The exotic clasts are mostly fractured fragments from various formations of the tectonic wedge (mostly Palaeocene to Miocene). The origin of the solid particles of the mud is polygenic, including deep Cretaceous-Palaeogene horizons close to the décollement, and various materials from the stratigraphic pile pierced by the mud conduits. Moreover, the fluids expelled by the mud volcanoes have a deep origin and notably the gas phase is thermogenic methane generated probably below a depth of 5000 m. The effusions occur either during cycles of moderate effusion of mud and fluids (quiescence regime), or during catastrophic events responsible for the expulsion of huge volumes of mud, clasts and fluids (transient regime). Available subsurface data suggest that the deep structure of the mud volcanoes includes: (1) a focused deep conduit at depth in the zone of overpressure; (2) a mud chamber intruding the surrounding formations around and above the top of the abnormal pressure zone; and (3) a superficial outlet leading to the surface vents.

Sterilisation properties of the Mars surface and atmospheric environment

The radiative and chemical conditions at the surface and in the lower Martian atmosphere are computed at various latitudes and seasons combining a 2D photochemical model and radiation simulations. In most situations, the solar UV B and C radiations reach the surface however, suspended dust and, in polar cases, ozone can constitute an effective UV shield. The daytime and night time concentrations of the sterilizing oxidants: OH, H2O2 and O3 are determined, as well as the concentration of the substances which could influence the metabolism of microorganisms. The possible habitats of a remaining Mar's life as well as the possibilities of contamination by resistant earth life forms will be described.

The relative prevalence of disease symptoms for ill persons: evidence from Benin

In developing countries, the usual modelling of the correlates of health problems is not a good fit for the health phenomena encountered and the available data. Indeed, three common situations occur: (a) it is often the observed symptoms that are used to determine medical interventions instead of specific disease diagnostics or general health indicators; (b) the ill persons described by the data are often affected by multiple health problems; and (c) the correlates of the full spectrum of all symptoms need to be considered together. In this paper, these issues are dealt with by proposing a statistical approach based on competing scores of symptoms that explain their relative prevalence among the observed ill persons. Using multinomial logit models, the relative prevalence of four symptoms was estimated for four age classes of ill persons in Benin. Socio-demographic characteristics, household equipment and consumption behaviour are shown to influence the relative prevalence of symptoms and therefore could be used to decide what treatment to use. Moreover, living standards and economic activities are important and the pattern of symptoms among poor or agricultural ill persons differs from that of the rich or the non-peasants. The proposed method can be used to assist the definition of target groups and to guide the allocation of scarce resources in poor countries.

Highly informative nature of inter simple sequence repeat (ISSR) sequences amplified using tri- and tetra-nucleotide primers from DNA of cauliflower (Brassica oleracea var. botrytis L.)

Inter simple sequence repeat (ISSR) sequences as molecular markers can lead to the detection of polymorphism and also be a new approach to the study of SSR distribution and frequency. In this study, ISSR amplification with nonanchored primer was performed in closely related cauliflower lines. Fourty-four different amplified fragments were sequenced. Sequences of PCR products are delimited by the expected motifs and number of repeats, which validates the ISSR nonanchored primer amplification technique. DNA and amino acids homology search between internal sequences and databases (i) show that the majority of the internal regions of ISSR had homologies with known sequences, mainly with genes coding for proteins implicated in DNA interaction or gene expression, which reflected the significance of amplified ISSR sequences and (ii) display long and numerous homologies with the Arabidopsis thaliana genome. ISSR amplifications revealed a high conservation of these sequences between Arabidopsis thaliana and Brassica oleracea var. botrytis. Thirty-four of the 44 ISSRs had one or several perfect or imperfect internal microsatellites. Such distribution indicates the presence in genomes of highly concentrated regions of SSR, or "SSR hot spots." Among the four nonanchored primers used in this study, trinucleotide repeats, and especially (CAA)5, were the most powerful primers for ISSR amplifications regarding the number of amplified bands, level of polymorphism, and their nature.

An 18-month clinical study of bond failures with resin-modified glass ionomer cement in orthodontic practice

The purpose of this study was to evaluate, over an 18-month period, the clinical performances of a resin-modified glass ionomer cement for bonding orthodontic brackets and to analyze various factors that influenced their survival and failure rates. Two orthodontists using the edgewise technique participated in this study; 6113 brackets, including 20 molar tubes, were bonded with Fuji Ortho LC (GC, Europe, N.V. Leuven, Belgium) in 135 patients. Ceramic, metal, and resin brackets were tested, and both operators used the same bonding method for the brackets. The survival rate and the failure rate of the brackets were evaluated. The rates were determined by operator, bracket type, tooth position in the dental arch, and age and sex of the patients. Bracket survival rates were estimated using the Kaplan-Meier test. The Cox-Mantel statistical test with a level of significance set at 0.05 was used to compare survival curves. The chi-square test was used at a level of P < .05 to compare failure rates. The overall failure rate for the sample was 7%, and the overall survival rate was equal to 0.918. Age had no significant influence on the failure rate (P = .07); however, it had a significant influence on the survival rate (P < .01). The best survival rates were obtained in the groups aged 16 to 20 years (S[t] = 0.943) and older than 20 years (S[t] = 0.929). The difference between males and females was not statistically significant in terms of failure rate (P = .17). However, the Cox-Mantel test showed a higher bracket survival rate for the males (S[t] = 0.924) than for the females (S[t] = 0.839) (P < .00001). The influence of the operator was not statistically significant on the failure rate (P = .08); however, it was significant on the survival rate (P < .0002). Location in the arch had a significant influence on the failure and survival rates. The worst results were obtained in the upper incisors and the canines, and the best results in the lower premolars. Fifteen percent of the molar tubes failed; their survival rate was equal to 0.833. The failure rate was significantly greater for resin brackets than for metal or ceramic brackets (P = .007). The highest survival rate was obtained with ceramic brackets (P = .0001). This in vivo study showed that bonding brackets and molar tubes with Fuji Ortho LC is compatible with clinical orthodontic practice.

Local increase in the number of mast cells and expression of nerve growth factor in the bronchus of asthmatic patients after repeated inhalation of allergen at low-dose

BACKGROUND

Repeated inhalation of allergen at low-dose induces an increase in bronchial hyper-responsiveness, without any associated symptom. The concomitant events in the bronchus have not been described.

OBJECTIVE

We have studied the dynamic number of mast cells in the airways of patients with mild asthma before and after repeated inhalation of allergen at low-dose and the expression of nerve growth factor (NGF), which is reported to promote growth and survival of mast cells.

METHODS

Twelve patients with mild asthma to cat allergen were enrolled at random in a blind placebo-controlled study, and submitted to repeated low-dose allergen exposure (1/5 of the provocative dose). Mast cells were immunolocalized using an antibody against mast cell tryptase. NGF and its high affinity receptor, TrkA, were immunolocalized using anti-NGF and anti-TrkA antibodies, respectively. NGF mRNA was quantified by competitive polymerase chain reaction (PCR) after reverse transcription of total RNA extracted from bronchial biopsy. NGF protein levels were measured by ELISA in bronchoalveolar lavage (BAL) fluid.

RESULTS

Bronchial mast cell number was increased significantly after allergen exposure as compared with before. NGF expression in the bronchus was immunolocalized mainly to epithelial cells, but also to fibroblasts, blood vessels, and a few infiltrated cells. NGF mRNA levels in bronchial biopsies were increased significantly after allergen exposure. The high affinity receptor for NGF, TrkA, was immunolocalized to the infiltrated mast cell membrane.

CONCLUSION

Our study shows that the increase in the number of mast cells and in the expression of NGF induced by allergen exposure in the bronchus of asthmatic patients is occurring before the onset of symptoms. In addition, our finding of the presence of the TrkA receptor on the membrane of the infiltrated mast cell in situ brings evidence of the mast cell as a target cell for the growth factor activity of NGF in the airways in asthma.

Meteorological simulations of boundary-layer structure during the 1996 Paso del Norte Ozone Study

Meteorological simulations centered around the border cities of El Paso and Ciudad Juárez have been performed during an ozone episode that occurred on August 13, 1996 during the 1996 Paso del Norte Ozone Study field campaign. Simulations were performed using the HOTMAC boundary-layer meteorological model using a 1, 2, 4 and 8-km horizontal grid size nested mesh system. Investigation of the vertical structure and evolution of the atmospheric boundary layer for the August 12-14 time period is emphasized in this paper due to its suspected importance in precipitating the ozone episode [Sci Total Environ (2001)]. This period was characterized by a slowly-evolving high pressure system over the region, a persistent upper-level jet at 2500-3500 m above ground level (agl), deep daytime mixed layer heights of 3500 m depth and unusually deep nighttime stable layers extending up to 2500 m above the ground. The fact that the boundary-layer growth stalled on the morning of August 13 relative to that on August 12 has been suggested as a possible reason for the ozone episode on the 13th. In addition, relatively weak surface-level winds were measured on August 13. Using both model results and experimental data we hypothesize explanations for the slower mixed-layer growth on the morning of the 13th and the stronger surface-level winds found on the 12th and 14th.

Inhibition of Ku heterodimer DNA end binding activity during granulocytic differentiation of human promyelocytic cell lines

The heterodimeric Ku protein (composed of the Ku 86 and Ku 70 sub-units) is a nuclear protein which binds to DNA termini without sequence specificity. Ku is the DNA-targeting component of the large catalytic sub-unit of the DNA-dependent protein kinase complex that is required for the repair of DNA double-strand breaks in mammalian cells. We studied the expression and function of Ku/DNA-PK during granulocytic differentiation of two human promyelocytic cell lines, HL60 and NB4, a process associated to decreased radiation resistance. After 3 days exposure to differentiating agents (either all-trans-retinoic acid or DMSO), Ku binding to double stranded (ds)-DNA ends declined dramatically whereas Ku protein levels remain unchanged. The nuclear, but not cytoplasmic, fraction of differentiated HL60 cells extracts exhibited a heat-sensitive inhibitory activity towards DNA binding of recombinant Ku heterodimer. We further demonstrate that immunoprecipitation of Ku is impaired in extracts from differentiated cells by using two antibodies that recognize epitopes within the C-terminus DNA binding domains of Ku 70 and Ku 86 proteins. These results favor the hypothesis of a protein interacting with Ku that would prevent DNA binding of heterodimerized Ku protein by steric hindrance.

A simple chemiluminescence-based method for rapid enumeration of Listeria spp. microcolonies

AIMS

Listeria monocytogenes is capable, under certain conditions, of producing chemiluminescence which is amplified by luminol. This property was used to detect and count microcolonies of Listeria spp. in a few hours, without the use of a microscope.

METHODS AND RESULTS

After trapping Listeria cells on polyvinylidene fluoride membranes, a chemiluminescence mixture was sprayed onto the membrane. The chemiluminescent spots emitted were analysed by a charge-coupled device camera connected to a data-processing system, which restored the intensity of the signals into three dimensional images. The intensity of the luminescence of microcolonies was improved by addition of cellobiose, and by brief exposure to u.v. light.

CONCLUSION

Microcolonies of Listeria spp. can be imaged and counted by luminol-enhanced chemiluminescence with a photon-counting system.

SIGNIFICANCE AND IMPACT OF THE STUDY

This method can be applied to the rapid detection and counting of Listeria spp. in raw milk.

Aberrant methylation during cervical carcinogenesis

We studied the pattern of aberrant methylation during the multistage pathogenesis of cervical cancers. We analyzed a total of 73 patient samples and 10 cervical cancer cell lines. In addition, tissue samples [peripheral blood lymphocytes (n = 10) and buccal epithelial cells (n = 12)] were obtained from 22 healthy volunteers. On the basis of the results of preliminary analysis, the cervical samples were grouped into three categories: (a) nondysplasia/low-grade cervical intraepithelial neoplasia (CIN; n = 37); (b) high-grade CIN (n = 17); and (c) invasive cancer (n = 19). The methylation status of six genes was determined (p16, RARbeta, FHIT, GSTP1, MGMT, and hMLH1). Our main findings are as follows: (a) methylation was completely absent in control tissues; (b) the frequencies of methylation for all of the genes except hMLH1 were >20% in cervical cancers; (c) aberrant methylation commenced early during multistage pathogenesis and methylation of at least one gene was noted in 30% of the nondysplasia/low-grade CIN group; (d) an increasing trend for methylation was seen with increasing pathological change; (e) methylation of RARbeta and GSTP1 were early events, p16 and MGMT methylation were intermediate events, and FHIT methylation was a late, tumor-associated event; and (f) methylation occurred independently of other risk factors including papillomavirus infection, smoking history, or hormone use. Although our findings need to be extended to a larger series, they suggest that the pattern of aberrant methylation in women with or without dysplasia may help identify subgroups at increased risk for histological progression or cancer development.

New dysostosis showing multilevel absence of vertebral pedicles: unique developmental anomaly of vertebral arches?

We report on an apparently normal child who shows hypopaplasia of the vertebral pedicles and posterior arches of several cervical, thoracic, and lumbar vertebrae with normally fused spinous apophyses, hypoplastic sacrum, lumbar epidural lipomatosis, synostoses of some cervical vertebral disks, and sacral spina bifida. The most likely mechanism is an abnormal differentiation of the spinal processes, due most probably to an absence of differentiation in cartilage of the dense mesenchyme forming their most anterior part. Because the anomalies affect multiple levels, we highly suspect a genetic basis to this unusual dysostosis affecting the development of the posterior sclerotomes.

Expression of intercellular adhesion molecule 1 (ICAM-1) on the human oviductal epithelium and mediation of lymphoid cell adherence

The epithelium of the human oviduct expresses the major histocompatibility complex (MHC) class II and shows endocytic properties towards luminal antigens. Therefore, the epithelial cells might behave as antigen-presenting cells, inducing a local immune response. The activation of antigen-specific T cells not only requires presentation of the peptide antigen by MHC class II, but also the presence of co-stimulatory molecules in the antigen-presenting cells. Therefore, the expression of the intercellular adhesion molecule 1 (ICAM-1) was examined in the epithelium of the human oviduct. Most oviducts showed epithelial ICAM-1 expression, as assessed by immunocytochemistry, western blot analysis and RT-PCR assay, and the expression was restricted to the luminal border of ciliated and secretory cells. Interferon gamma, interleukin 1 and lipopolysaccharide treatments increased the percentage of ICAM-1-positive cells in primary cultures, indicating that the expression of ICAM-1 in the oviduct might be upregulated in vivo by inflammatory cytokines or bacterial infections. Binding assays between allogenic phytohaemagglutinin-activated lymphocytes and epithelial monolayers expressing ICAM-1 demonstrated that this molecule stimulated lymphocyte adherence. The presence of ICAM-1, in addition to MHC class II, supports the putative role of the oviductal epithelium in antigen presentation. The exclusive apical distribution of ICAM-1 indicates that T-cell activation would occur in a polarized manner. Binding of lymphoid cells to the surface of the oviductal epithelium may help to retain these immune cells that are required for the clearance of pathogens.

Decreased DNA-PK activity in human cancer cells exhibiting hypersensitivity to low-dose irradiation

Low-dose hyper-radiosensitivity (HRS) (below 0.5 Gy) has been extensively documented in the past few years. The molecular basis of this phenomenon remains largely unknown and the purpose of this study was to investigate the possible implication of the DNA repair DNA-PK complex. The activity of the DNA-PK complex, i.e. Ku DNA-end binding activity and kinase activity of the whole complex, was studied in 10 human cancer cell lines, 2 h after 0.2, 0.5 and 1 Gy irradiation. After low-dose irradiation (0.2 Gy), a marked decrease in DNA-PK activity was found in all six cell lines exhibiting HRS, whereas the DNA-PK activity was increased in the four cell lines which did not exhibit HRS. This modulation of DNA-PK activity was a rapid phenomenon occurring within the 2 h following low-dose radiation exposure. These data strongly suggest the implication of the DNA-PK repair complex in the HRS phenomenon.

Treatment of hepatocellular cancer with the long acting somatostatin analog lanreotide in vitro and in vivo

Based on the fact that somatostatin (SST) analogs have given promising results for treatment of hepatocellular cancer, we performed both in vitro and in vivo investigations to define the role of a depot formulation of the long acting SST-analog lanreotide (LAN). A decrease of cells in the S-phase as compared to controls (p<0.03) followed by a significant, dose-dependent induction of apoptosis could be demonstrated in Hep G2 cells along with a dose-dependent influence of the peptide on cellular proliferation. Northern blotting demonstrated the presence of mRNA for SSTR subtypes 2, 3 and 4 in Hep G2 cells, but only slight SSTR expression in normal liver tissue. In addition, 21 untreated patients with advanced HCC not amenable to surgery were administered 30 mg of LAN by deep intramuscular injection every 14 days until documented disease progression. Fifteen of these patients also underwent scanning with commercially available 111In-DTPA-D-Phe1-Octreotide (111In-OCT) to define the in vivo expression of SSTR. No positive 111In-OCT scans were obtained, indicating the absence of relevant amounts of functional SSTR2 in HCC. One patient (5%) showed a partial response to treatment, 8 patients had stable disease (38%), while the remaining patients progressed during treatment. The median survival was 4.2 months (range 1.2-13+), and the median time to progression was 2.5 months (range, 1.5-7+). However, 4 patients (19%) had an increase in WHO performance status lasting between 2.5 and 6 months, 5 patients (24%) had an increase in body weight, while pain markedly improved in 1 additional patient (5%). In total, 5 patients (24%) had a decrease in serum-AFP levels by at least 30%. Our results clearly indicate the ability of LAN to decrease the S-phase fraction along with induction of apoptosis in Hep G2 cells in a dose-dependent manner. Our data suggest clinical potential of SST-analogs in HCC and indicate that suboptimal doses of the peptide might have been administered in our series.

Transfer of Ku86 RNA antisense decreases the radioresistance of human fibroblasts

Ku86 has been shown to be involved in DNA double-strand break (DSB) repair and radiosensitivity in rodents, but its role in human cells is still under investigation. The purpose of this study was to evaluate the radiosensitivity and DSB repair after transfection of a Ku86-antisense in a human fibroblast cell line. Simian virus 40-transformed MRC5V1 human fibroblasts were transfected with a vector (pcDNA3) containing a Ku86-antisense cDNA. The main endpoints were Ku86 protein level, Ku DNA end-binding and DNA protein kinase activity, clonogenic survival, and DSB repair kinetics. After transfection of the Ku86-antisense, decreased Ku86 protein expression, Ku DNA end-binding activity, and DNA protein kinase activity were observed in the uncloned cellular population. The fibroblasts transfected with the Ku86-antisense showed also a radiosensitive phenotype, with a surviving fraction at 2 Gy of 0.29 compared with 0.75 for the control and 20% of unrepaired DSB observed at 24 hours after irradiation compared with 0% for the control. Several clones were also isolated with a decreased level of Ku86 protein, a surviving fraction at 2 Gy between 0.05 and 0.40, and 10-20% of unrepaired DSB at 24 hours. This study is the first to show the implication of Ku86 in DSB repair and in the radiosensitivity of human cells. This investigation strongly suggests that Ku86 could constitute an appealing target for combining gene therapy and radiation therapy.

Cidofovir, a new approach for the treatment of cervix intraepithelial neoplasia grade III (CIN III)

Cervix intraepithelial neoplasia grade III (CIN III) is an intraepithelial proliferative process with different levels of severity depending on both the extension of the proliferation in the epithelium and the presence of cellular atypia. Human papillomavirus (HPV) has been clearly associated with such lesions. The results of a preliminary study are described on the local application of cidofovir, an acyclic nucleoside phosphonate derivative with broad-spectrum anti-DNA virus activity for the treatment of CIN III. Cidofovir 1% in gel was applied three times, every other day, on the cervix of each of 15 women with biopsy proven CIN III. Within 1 month after the start of treatment, the cervix was removed surgically. Histology and human papillomavirus polymerase chain reaction (HPV-PCR) were carried out. In 7 of the 15 patients the histology showed a complete response, whereas 5 patients had a partial response characterized by the persistence of CIN II-III lesions, 1 patient had a dysplasia of lower grade (CIN I), and 2 patients did not show differences in the histology. Complete response was confirmed by PCR in 4 of the 7 patients, with complete response histologically. Cidofovir was not toxic to the normal epithelium. Cidofovir 1% gel was able to inhibit partially or completely cervical dysplasia lesions after only three applications (every other day). This effect was specific and tissue other than the dysplastic epithelium was not affected by the treatment.

The activity of the DNA-dependent protein kinase (DNA-PK) complex is determinant in the cellular response to nitrogen mustards

The DNA-dependent protein kinase plays a critical role in mammalian DNA double strand break (DSB) repair and in specialized recombination, such as lymphoid V(D)J recombination. Its regulatory subunit Ku (dimer of the Ku70 and Ku80 protein) binds to DNA and recruits the kinase catalytic sub-unit, DNA-PKcs. We show here that three different strains deficient in either the Ku80 (xrs-6) or DNA-PKcs (V-3, scid) component of DNA-PK are markedly sensitive (3.5- to 5-fold) to a group of DNA cross-linking agents, the nitrogen mustards (NMs) (melphalan and mechlorethamine) as compared to their parental cell line. Importantly, the level of hypersensitivity to these drugs was close to the level of hypersensitivity observed for radiomimetic agents that create DSBs in DNA (bleomycin and neocarzinostatin). In addition, sensitivity to NMs was restored to the parental level in the xrs-6 cell line stably transfected with the human Ku80 gene (xrs-6/Ku80), showing unequivocally that DNA-PK is involved in this phenotype. These results indicate that a function of the whole DNA-PK protein complex is involved in the cellular response to NMs and suggest that the repair of DNA interstrand cross-links induced in DNA by NMs involved a DNA-PK dependent pathway that shares common features with DNA DSBs repair.

[DNA-dependent protein kinase: a major protein involved in the cellular response to ionizing radiation]

DNA-dependent protein kinase (DNA-PK) is a DNA-activated nuclear serine/threonine protein kinase. DNA-PK consists of a regulatory sub-unit, the heterodimeric Ku protein (composed of a 70- and a 86-kDa subunit) which binds DNA ends and targets the catalytic sub-unit, DNA-PKcs to DNA strand breaks. DNA-PK plays a major role in the repair of double-strand breaks induced in DNA after exposure to ionizing radiation as shown by the extreme radiosensitivity of cells with mutations in Ku86, Ku70 or DNA-PKcs genes. Cells deficient in DNA-PK activity also exhibit hypersensitivity to genotoxic drugs such as cisplatin and nitrogen mustards. In the first part of this review, the current knowledge on the biochemical characteristics of DNA-PK, its mechanism of action in DNA repair and the phenotype of DNA-PK deficient cells is summarized. These results suggest that DNA-PK might play a role in the acquisition of a resistant phenotype of human tumors to radiotherapy, chemotherapy using genotoxic drugs or to both treatments. In the second part of this review, the studies devoted to inhibition of DNA-PK in order to enhance cancer therapy by DNA-damaging agents are presented.

Gamma-hydroxybutyrate and cocaine administration increases mRNA expression of dopamine D1 and D2 receptors in rat brain

The effects of acute and repeated gamma-hydroxybutyrate (GHB) and cocaine administration on D1 and D2 dopamine receptor mRNA expression were examined using in situ hybridization histochemistry in different rat brain structures rich in GHB receptors. Six hours after a single GHB administration (500 mg/kg i.p.), an increase in D1 and D2 mRNA expression was observed in almost all regions examined; whereas, acute cocaine injection (20 mg/kg i.p.) had no effect. Repeated exposure to GHB (500 mg/kg i.p. twice daily) for 10 days, followed by a 14-h withdrawal period, induced increasing effects on D1 and D2 dopamine receptor mRNA expression, similar to those caused by chronic treatment with cocaine (20 mg/kg i.p. once a day). These effects of GHB and cocaine on dopamine receptor mRNA expression could be a consequence, for both compounds, of the modulation of dopaminergic activity; thus, supporting the benefit of GHB in cocaine substitution therapy.