Ecstasy (MDMA)-induced hyponatraemia is associated with genetic variants in CYP2D6 and COMT.

We hypothesised that genetically determined poor metabolism of 3,4-methylene dioxymetamphetamine (MDMA) due either to the presence of CYP2D6 genotypes giving absent or low CYP2D6 enzyme activity, or a COMT genotype predicting low COMT enzyme activity would be associated with a greater degree of MDMA-induced reduction in plasma sodium and osmolality than other genotypes at these genes following consumption of 'ecstasy' tablets by clubbers. Of the 48 subjects who returned to the test site post-clubbing, 30 provided samples for measurement of vasopressin (AVP), plasma sodium, urea and plasma and urine osmolality. Genotyping was performed for functional variants in CYP2D6 (n = 29) and COMT (Val158Met, n = 30). In subjects with urinary MDMA detected post-clubbing, there was a significant association between change in plasma osmolality (p = 0.009) and in plasma sodium (p = 0.012) and CYP2D6 genotypic category. Individuals with the low-activity but readily inhibitable CYP2D6 extensive metaboliser/intermediate metaboliser (EM/IM) genotype showed greater reductions in these measures than all other CYP2D6 genotypic categories. COMT low-activity genotypes (Met/Met and Val/Met) were also significantly associated with reductions in plasma osmolality (p = 0.028) and in plasma sodium (p = 0.003). On conservative Bonferroni correction for two independent genes, the CYP2D6 and COMT plasma sodium findings remain significant. The relatively high frequency of the low-activity CYP2D6 and COMT genotypes in the population warrants further attention, since consumption of free water following ingestion of MDMA in these individuals may trigger dilutational hyponatraemia and increased risk of syndrome of inappropriate antidiuretic hormone secretion.

Pharmacogenetic studies of change in cortisol on ecstasy (MDMA) consumption.

In this study we investigate the association of cytochrome P450 enzyme CYP2D6, catechol-O-methyl transferase (COMT, Val158Met) and serotonin transporter promoter (5-HTTLPR) genotypes on change in cortisol concentration following 3, 4-methylenedioxy-methamphetamine (MDMA, 'ecstasy') consumption. Forty-eight subjects (30 males, mean age 23 years), self-nominating regular clubbers provided 'in the field' pre- and post-clubbing biological samples and associated information. Of the 39 subjects who provided a post-clubbing urine sample, 21 were positive for MDMA. Plasma cortisol concentrations increased in subjects (n = 48) tested for cortisol, with changes being significantly greater in the MDMA-positive group (736.9 ± 83.2 vs. 350.9 ± 34.5 mmol/l, p = 0.001). We found a positive association between the low activity COMT genotype (Met/Met) and MDMA-induced change in cortisol and also between this and change in cortisol in the whole sample (p = 0.039, Bonferroni corrected). For CYP2D6, there was an association between genotype and change in cortisol, confined to subjects with MDMA-positive urine post-clubbing (p = 0.003, Bonferroni corrected). There was no association with 5-HTTLPR genotype. These associations suggest that chronic use of MDMA may lead to HPA axis dysregulation and that the magnitude of this may be moderated by genetic polymorphism, and warrant further investigation in a larger sample of those who consume the drug on a regular basis.

Stargazin involvement with bipolar disorder and response to lithium treatment.

OBJECTIVES: Multiple reports have implicated chromosomal region 22q13.1 in both schizophrenia and bipolar disorder. The calcium channel gamma-2 subunit gene (cacng2, Stargazin) located on 22q13.1 was recently reported to be associated with schizophrenia. We aimed to examine the expression levels of Stargazin in post-mortem brain samples of patients with schizophrenia, patients with bipolar disorder (BPD) and healthy controls, test for genetic association between Stargazin and these disorders and test for genetic association between Stargazin and response to lithium treatment. METHODS: Expression analysis was carried out by quantitative reverse transcription-PCR in RNA samples from dorsolateral prefrontal cortices of patients with schizophrenia, patients with BPD and controls (n=35 each). Twelve single nucleotide polymorphisms encompassing Stargazin were genotyped in DNA samples from two cohorts, 'Aberdeen' and 'Cagliari' (n=410, 170, respectively). Patients were treated with lithium and divided into groups according to their response. RESULTS: A 1.6-fold overexpression of Stargazin was observed in patients with BPD (P=0.000036). No difference in expression was observed in patients with schizophrenia. None of the 12 genotyped single nucleotide polymorphisms were associated with BPD, but three of them were significantly associated with lithium response: one in both cohorts (rs2284017) and two (rs2284018, rs5750285) each in a different cohort. Haplotype analysis revealed significant 'response-protective' and 'response-inhibitive' haplotypes in both cohorts. CONCLUSION: Our findings suggest that Stargazin dysregulation may be involved with the pathophysiology of BPD, but not with that of schizophrenia, and that Stargazin polymorphisms may play a role in the response to lithium treatment.

An investigation of the alpha1A-adrenergic receptor gene and antipsychotic-induced side-effects.

Antipsychotic treatment is hampered by the induction of side-effects such as tardive dyskinesia (TD), weight gain, sedation and extrapyramidal side-effects (EPS). Identification of the factors related to their development would facilitate their avoidance and the improvement of antipsychotic treatment. It has been hypothesised that genetic variants in drug targeted receptors may contribute to the development of side-effects. In this study, we have investigated the possible influence of genetic variants (-563-C/T, -4155-G/C and -4884-A/G) of the alpha(1A)-adrenergic receptor, an important target of atypical antipsychotic drugs, and development of side-effects after antipsychotic medication in a sample of N = 427 US Caucasian patients. We found several marginal associations (p < 0.05) between alpha(1A)-adrenergic genetic variants and antipsychotic-induced side-effects which did not reach statistical significance after corrections for multiple analyses. These results do not support a major role of alpha(1A)-adrenergic genetic variants in obesity and other side-effects observed after prolonged treatment with antipsychotic medications.

Association of the dysbindin gene with bipolar affective disorder.

OBJECTIVE: In the study of bipolar affective disorder and schizophrenia, there is some evidence suggesting a phenotypic and genetic overlap between the two disorders. A possible link between bipolar affective disorder and schizophrenia remains arguable, however. The authors hypothesized that dysbindin, which is a probable susceptibility gene for schizophrenia, was associated with bipolar affective disorder and tested this hypothesis using a case-control design study. METHOD: Participants included 213 patients with bipolar I disorder and 197 comparison subjects. In each subject, 10 polymorphisms in the dysbindin gene were genotyped and assessed. RESULTS: Two polymorphisms showed individual genotypic association with bipolar I disorder. Multiple marker haplotypes were more strongly associated, with the rarer of the two common haplotypes being overrepresented in the patients with bipolar affective disorder. A similar finding was reported in patients with schizophrenia in a previous study. CONCLUSIONS: Findings suggest that the human dysbindin gene may play a role in the susceptibility to bipolar affective disorder, which underscores a potentially important area of etiological overlap with schizophrenia. The existence of shared genetic risk factors will, in time, lead to changes in the current nosology of major psychoses.

Lithium and clozapine rechallenge: a retrospective case analysis.

BACKGROUND: Clozapine is a uniquely effective antipsychotic, although its use is limited by the risk of neutropenia. Lithium is occasionally prescribed during a clozapine rechallenge, with the hope that it will prevent a second neutropenia or agranulocytosis. There are concerns, however, that lithium use will mask the onset of a neutropenia, leading to a more severe dyscrasia. The objective of this analysis was to determine the utility and safety of lithium coprescription in clozapine rechallenge. METHOD: A retrospective case analysis was performed of all patients who had experienced a previous clozapine-induced blood dyscrasia and had a clozapine rechallenge with lithium coprescribed in a tertiary referral center between September 1998 and September 2003. RESULTS: Twenty-five patients met the study criteria; 1 patient (4%) had a second episode of neutropenia or agranulocytosis while undergoing the rechallenge. This rate was significantly lower (p = .021) than the national (U.K.) rate (21.2%). Although recurrent dyscrasias were not more common, or more severe, than those seen with rechallenge in general, our single case did show some evidence that the patient's neutropenia was masked by lithium use. CONCLUSION: This study provides support for the utility of lithium in preventing neutropenias in rechallenge; extra vigilance may be required, however, to detect masked blood dyscrasias.

Expression of the alpha1A-adrenergic receptor in schizophrenia.

The alpha1-adrenergic receptors may contribute to cognitive functions relevant to schizophrenia. Following the discovery of an association between polymorphisms in the regulatory region of the alpha1A-adrenergic receptor and schizophrenia we investigated the expression of mRNA for this receptor between schizophrenics (n=19) and controls (n=19) using a TaqMan approach in post-mortem brains. No differences were found suggesting that mRNA levels are not altered in schizophrenia. Genotypic data for the subjects found that possession of the previously associated genotypes did not convey a difference in mRNA expression suggesting that these polymorphisms do not affect the level of transcription.

Is there cognitive impairment in clinically 'healthy' abstinent alcohol dependence?

AIMS: The aim of this study was to determine neuropsychological performance in apparently cognitively, mentally, and physically healthy abstinent alcohol-dependent subjects compared with control subjects who were recruited for a number of different neuroimaging studies. METHODS: All subjects completed a battery of neuropsychological tests as part of the neuroimaging protocol. RESULTS: The group dependent on alcohol performed as well as controls on a non-verbal memory test and verbal fluency but performed worse in the verbal memory task, Trail A + B, and total IQ derived from Silverstein's short-form of the WAIS-R. However, the IQ performance of both groups was above average. In both groups, age was associated with slower performance on the Trail A + B task. In the alcohol-dependent group, severity of dependence and length of abstinence was not associated with performance of any task. CONCLUSIONS: In this apparently clinically healthy population of abstinent alcohol-dependent subjects, frontal lobe dysfunction was detectable using the Trail A + B and digit symbol tasks. This was despite above-average WAIS-R IQ scores. Consideration needs to be given to routine incorporation of cognitive testing in alcohol dependence since subtle deficits may not be easily apparent and may impact on treatment outcome.

Role of chronic infection and inflammation in the gastrointestinal tract in the etiology and pathogenesis of idiopathic parkinsonism. Part 1: eradication of Helicobacter in the cachexia of idiopathic parkinsonism.

BACKGROUND: Neuronal damage in idiopathic parkinsonism may be in response to ubiquitous occult infection. Since peptic ulceration is prodromal, Helicobacter is a prime candidate. AIM: To consider the candidature of Helicobacter in parkinsonism with cachexia. METHODS: We explore the relationship between being underweight and inflammatory products in 124 subjects with idiopathic parkinsonism and 195 controls, and present the first case-series evidence of efficacy of Helicobacter eradication, in parkinsonism advanced to the stage of cachexia. RESULTS: Association of a low body mass index with circulating interleukin-6 was specific to parkinsonism (p = .002), unlike that with antibodies against Helicobacter vacuolating-toxin and cytotoxicity-associated gene product (p < .04). Marked reversibility in both cachexia and disability of idiopathic parkinsonism followed Helicobacter heilmannii eradication in one case, Helicobacter pylori eradication in another, follow-up being > or = 3.5 years. The latter presented with postprandial bloating, and persistent nausea: following eradication, radioisotope gastric-emptying returned towards normal, and upper abdominal symptoms regressed. Reversibility of their cachexia/disability contrasts with the outcome of anti-Helicobacter therapy where eradication repeatedly failed (one case), and in non-Helicobacter gastritis (three cases). Anti-parkinsonian medication remained constant. Intestinal absorption and barrier function were normal in all. CONCLUSION: Categorization, according to presence or absence of Helicobacter infection, was a useful therapeutic tool in late idiopathic parkinsonism.

Role of chronic infection and inflammation in the gastrointestinal tract in the etiology and pathogenesis of idiopathic parkinsonism. Part 2: response of facets of clinical idiopathic parkinsonism to Helicobacter pylori eradication. A randomized, double-blind, placebo-controlled efficacy study.

BACKGROUND: Links between etiology/pathogenesis of neuropsychiatric disease and infection are increasingly recognized. AIM: Proof-of-principle that infection contributes to idiopathic parkinsonism. METHODS: Randomized, double-blind, placebo-controlled efficacy study of proven Helicobacter pylori eradication on the time course of facets of parkinsonism. Intervention was 1 week's triple eradication therapy/placebos. Routine deblinding at 1 year (those still infected received open-active), with follow-up to 5 years post-eradication. Primary outcome was mean stride length at free-walking speed, sample size 56 for a difference, active vs. placebo, of 3/4 (between-subject standard deviation). Recruitment of subjects with idiopathic parkinsonism and H. pylori infection was stopped at 31, because of marked deterioration with eradication failure. Interim analysis was made in the 20 who had reached deblinding, seven of whom were receiving antiparkinsonian medication (long-t(1/2), evenly spaced) which remained unchanged. RESULTS: Improvement in stride-length, on active (n = 9) vs. placebo (11), exceeded size of effect on which the sample size was calculated when analyzed on intention-to-treat basis (p = .02), and on protocol analysis of six weekly assessments, including (p = .02) and excluding (p = .05) those on antiparkinsonian medication. Active eradication (blind or open) failed in 4/20, in whom B-lymphocyte count was lower. Their mean time course was: for stride-length, -243 (95% CI -427, -60) vs. 45 (-10, 100) mm/year in the remainder (p = .001); for the ratio, torque to extend to flex relaxed arm, 349 (146, 718) vs. 58 (27, 96)%/ year (p < .001); and for independently rated, visual-analog scale of stance-walk videos (worst-best per individual identical with 0-100 mm), -64 vs. -3 mm from anterior and -50 vs. 11 lateral (p = .004 and .02). CONCLUSIONS: Interim analysis points to a direct or surrogate (not necessarily unique) role of a particular infection in the pathogenesis of parkinsonism. With eradication failure, bolus release of antigen from killed bacteria could aggravate an effect of ongoing infection.

Polymorphisms in the promoter region of the alpha1A-adrenoceptor gene are associated with schizophrenia/schizoaffective disorder in a Spanish isolate population.

BACKGROUND: Animal models have implicated the alpha(1)-adrenergic subtypes in cognitive functions relevant to schizophrenia, but no consensus exists with regard to the status of noradrenergic receptor populations in psychiatric patients. We focused on one alpha(1)-adrenergic subtype, the alpha(1A)-adrenergic receptor, and proposed that genetic variants within the regulatory region of this gene (ADRA1A) alter the expression of this receptor, influencing susceptibility toward schizophrenia. METHODS: This study examined this proposal by testing the hypothesis that single nucleotide polymorphisms (SNPs) in the promoter region of the alpha(1A)-adrenergic gene were associated with schizophrenia by performing case-control association analysis on SNPs found in a 5' upstream region, which included the putative promoter region and 5' untranslated region. Our sample consisted of 103 schizophrenia and 14 schizoaffective disorder patients and 176 control subjects. All recruits were from a Spanish population isolate of Basque origin that is characterized by low heterogeneity, which was selected with the intent that it might facilitate the identification of disease-related polymorphisms. RESULTS: A total of eight SNPs (-9625 G/A, -7255 A/G, -6274 C/T, -4884 A/G, -4155 C/G, -2760 A/C, -1873 G/A, and -563 C/T) were confirmed at a rare allele frequency of >5%. Association with schizophrenia and schizoaffective disorder was found for the -563 C/T SNP (p = .0005 for allele and p = .007 for genotype, Bonferroni corrected) and -9625 G/A SNP (p = .02 for allele and p = .03 for genotype, Bonferroni corrected). Significant differences in the 54 haplotypes formed by these eight SNPs were also found between patients and control subjects (p = .008, Bonferroni corrected). CONCLUSIONS: Because of the strength of these results and the location of these SNPs in the regulatory region of this gene, functional studies investigating the possible influence of these SNPs on receptor expression levels in schizophrenia are warranted.

Cost analysis of treating schizophrenia with amisulpride: naturalistic mirror image study.

The aim of the study was to examine the costs of schizophrenia treatment using the atypical antipsychotic amisulpride relative to treatment with other antipsychotics. Service use data were collected for one year of amisulpride treatment. The patients were also assessed with the Global Assessment of Functioning (GAF) scale and scales of Quality of Life. These were compared with retrospectively collected data for the 1-year period prior to the patients commencing amisulpride. The findings indicate that, compared with the year before, the clinical and quality of life scores improved during the year of treatment with amisulpride. There was a numerical reduction of total costs, as well as costs of in- and out-patient service use per patient per year during the year on amisulpride compared with the year before the patients started amisulpride. Patients on amisulpride spent fewer days as acute in-patients, but stayed longer in rehabilitation wards. Amisulpride treatment may lead to a reduction in the cost of treating schizophrenia in comparison with treatment with other antipsychotic medications.

Association between dopamine D3 receptor gene polymorphisms and schizophrenia in an isolate population.

There are several lines of evidence implicating the dopamine D3 receptor in the pathophysiology of schizophrenia. The Ser9Gly polymorphism of the dopamine D3 receptor gene (DRD3) has been the most extensively investigated DRD3 variant in connection with the disease but results have been inconclusive. Recent reports indicate that the Ser9Gly polymorphism is in linkage disequilibrium with other markers, but association studies between DRD3 haplotypes and schizophrenia have had mixed results. Genetic heterogeneity may be one of the causes of contradicting results. In order to clarify the role of DRD3 alterations in the aetiology of disease, we have investigated three D3 genetic variants (Ser9Gly, -205-G/A, -7685-G/C) in a sample of patients with schizophrenia or schizoaffective disorder (N=118) and controls (N=162) recruited from a human isolate from Navarra (Northern Spain) of Basque origin. Although no association was found between the Ser9Gly or the -205-A/G polymorphisms and disease, an excess of allele -7685-C was observed in patients (p=0.002 after correction for multiple analyses). Haplotype analysis shows the three markers to be in strong linkage disequilibrium (p<0.0001) and strongly associated with disease (p<1x 10(-5)). These results may suggest that these polymorphisms exert a combined or synergistic effect on susceptibility to schizophrenia, or are in linkage with an unknown causative factor. However, further replication in independent samples is required.

The -1438A/G polymorphism in the 5-hydroxytryptamine type 2A receptor gene affects promoter activity.

BACKGROUND: The -1438A/G single nucleotide polymorphism (SNP) lies just upstream of two alternative promoters for the 5-hydroxytryptamine type 2A (5-HT2A) receptor gene (HTR2A) and is in strong linkage disequilibrium with the 102T/C SNP. Both SNPs are associated with numerous psychiatric disorders and related phenotypes. A possible functional affect of the -1438A/G SNP might underlie associations of both linked SNPs with these neuropsychiatric disorders. A prior investigation into affects of this SNP on promoter function, lacking the more downstream promoter, found no significant difference with a reporter gene assay. METHODS: To investigate possible functional effects of -1438A/G on either promoter, two different reporter gene assays were used in three cell lines. RESULTS: Promoter activity was consistently detected that, in the presence of the SV40 enhancer, was significantly greater in the presence of the A allele relative to the G allele but only in cell lines that express endogenous HTR2A, suggesting that transcriptional factor(s) and the presence of both promoters might be necessary to elicit this effect. CONCLUSIONS: These findings show that the -1438A/G SNP has the potential to modulate HTR2A promoter activity and might be the functional variant responsible for the associations of both SNPs with many neuropsychiatric phenotypes.

Four days of citalopram increase suppression of cortisol secretion by prednisolone in healthy volunteers.

RATIONALE: Chronic antidepressant treatment increases glucocorticoid-mediated negative feedback on the hypothalamic-pituitary-adrenal (HPA) axis, and thus reduces HPA axis activity, in depressed patients and healthy controls. In contrast, acute antidepressant treatment induces an activation of basal HPA axis activity. OBJECTIVES: We examined the effects of 4 days of treatment with the selective serotonin reuptake inhibitor, citalopram, on basal salivary cortisol and on suppression of salivary cortisol by prednisolone. METHODS: We used a single-blind, placebo-controlled, repeated-measure design. Salivary cortisol was measured from 0900 to 1700 hours. In the first phase of the study, basal salivary cortisol secretion was measured on 2 study days, before and after 4 days of treatment with citalopram (orally, 20 mg/day). In the second phase, salivary cortisol secretion after suppression by prednisolone (5 mg, given at 2200 hours the night before) was measured on 2 study days, again before and after 4 days of treatment with citalopram (orally, 20 mg/day). Eight volunteers participated to the study. RESULTS: Citalopram increased basal salivary cortisol in the morning (0900-1100 hours) by approximately 47% (P=0.003). Moreover, citalopram increased suppression by prednisolone in the morning (0900-1100 hours): suppression was approximately 22% before citalopram and 45% after citalopram (P=0.05). CONCLUSIONS: Citalopram increases glucocorticoid-mediated negative feedback on the HPA axis after as little as 4 days of treatment. This effect could be due to an increased function of the corticosteroid receptors. Our findings further support the notion that one of the mechanisms by which antidepressants exert their therapeutic effects is by normalizing HPA axis hyperactivity in depressed patients.

Do antidepressants regulate how cortisol affects the brain?

Although the effects of antidepressants on glucocorticoid hormones and their receptors are relevant for the therapeutic action of these drugs, the molecular mechanisms underlying these effects are unclear. Studies in depressed patients, animals and cellular models have demonstrated that antidepressants increase glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) expression and function; this, in turn, is associated with enhanced negative feedback by endogenous glucocorticoids, and thus with reduced resting and stimulated hypothalamic-pituitary-adrenal (HPA) axis activity. In a series of studies conducted over the last few years, we have shown that antidepressants modulate GR function in vitro by inhibiting membrane steroid transporters that regulate the intracellular concentration of glucocorticoids. In this paper, we will review the effects of membrane steroid transporters and antidepressants on corticosteroid receptors. We will then present our unpublished data on GR live microscopy in vitro, showing that ligand-induced translocation of the GR starts within 30 seconds and is completed within minutes. Furthermore, we will present our new data using an in situ brain perfusion model in anaesthetised guinea-pigs, showing that entry of cortisol to the brain of these animals is limited at the blood-brain barrier (BBB). Finally, we will present a comprehensive discussion of our published findings on the effects of chemically unrelated antidepressants on membrane steroid transporters, in mouse fibroblasts and rat cortical neurones. We propose that antidepressants in humans could inhibit steroid transporters localised on the BBB and in neurones, like the multidrug resistance p-glycoprotein, and thus increase the access of cortisol to the brain and the glucocorticoid-mediated negative feedback on the HPA axis. Enhanced cortisol action in the brain might prove to be a successful approach to maximise therapeutic antidepressant effects.

Is clozapine antisuicidal?

Suicide accounts for approximately 10% of patient deaths in schizophrenia. The atypical antipsychotic clozapine (Clozaril), successful in treatment-resistant patients with schizophrenia, may have an additional antisuicidal effect. Numerous published reports, including the collaborative International Suicide Prevention Trial, have compared mortality rates between clozapine recipients and patients receiving other forms of antipsychotic treatment and observed a significant reduction in patient risk for suicide with clozapine therapy. Preliminary reports indicate improvements in suicidality in schizophrenia patients treated with other modern atypical antipsychotics, for example olanzapine [Zyprexa], risperidone [Risperdal] and sertindole [Serdolect], but further investigation is required to clarify their role as antisuicidal drugs. It has been estimated that 53 suicides in treatment-resistant patients could have been prevented by clozapine, but the number of lives saved may be significantly higher if clozapine therapy was extended to treatment responders at a high risk for suicide.

Antidepressant fluoxetine enhances glucocorticoid receptor function in vitro by modulating membrane steroid transporters.

1. Incubation of LMCAT fibroblast cells with antidepressants potentiates glucocorticoid receptor (GR)-mediated gene transcription in the presence of dexamethasone and cortisol, but not of corticosterone. We have shown that antidepressants do so by inhibiting the LMCAT cell membrane steroid transporter (which is virtually identical to the multidrug resistance P-glycoprotein) and thus by increasing dexamethasone or cortisol intracellular concentrations. However, previous experiments with the antidepressant fluoxetine in the presence of dexamethasone have produced negative results (Pariante et al. (2001). Br. J. Pharmacol., 134, 1335-1343). 2. We have since re-examined the effects of fluoxetine on GR-mediated gene transcription in the presence of dexamethasone. Moreover, we have examined the effects of fluoxetine on GR-mediated gene transcription in the presence of cortisol and corticosterone, and on the intracellular accumulation of radioactive cortisol and corticosterone. Finally, we have examined the effects of fluoxetine on inhibition of P-glycoprotein activity in Caco-2 cells. 3. We now find that fluoxetine (1-10 micro M) enhances GR-mediated gene transcription in the presence of dexamethasone and cortisol (+140-170%), but not of corticosterone, and increases the intracellular accumulation of (3)H-cortisol (+5-15%), but not of (3)H-corticosterone. Moreover, fluoxetine (10 micro M) induces approximately 30% inhibition of PGP activity in Caco-2 cells. 4. Our results show that fluoxetine, like other antidepressants, inhibits membrane steroid transporters.

The antidepressant clomipramine regulates cortisol intracellular concentrations and glucocorticoid receptor expression in fibroblasts and rat primary neurones.

Incubation of LMCAT fibroblasts cells with antidepressants potentiates glucocorticoid receptor (GR)-mediated gene transcription in the presence of cortisol, but not of corticosterone. We have suggested that antidepressants do so by inhibiting the LMCAT cells membrane steroid transporter and thus by increasing cortisol intracellular concentrations. We now confirm and extend this model to primary neuronal cultures. Clomipramine, a tricyclic antidepressant, increased the intracellular accumulation of 3H-cortisol, but not 3H-corticosterone, in LMCAT cells (+80%) and primary rat neurones (+20%). The latter finding is the first demonstration that a membrane steroid transporter is present in neurones. Moreover, verapamil, a membrane steroid transporter inhibitor, reduced the effects of clomipramine on the intracellular accumulation of 3H-cortisol in LMCAT cells. Finally, clomipramine also decreased GR expression (whole-cell Western blot) in LMCAT cells (50% reduction) and primary rat neurones (80% reduction). This GR downregulation can explain the reduced GR-mediated gene transcription previously described under experimental conditions that do not elicit the effects on the LMCAT cells steroid transporter. This work further supports the hypothesis that membrane steroid transporters regulating the access of glucocorticoids to the brain in vivo are a fundamental target for antidepressant action.