Hannelore Ehrenreich

Specific attentional dysfunction in adults following early start of cannabis use

Rationale and objective: The present study tested the hypothesis that chronic interference by cannabis with endogenous cannabinoid systems during peripubertal development causes specific and persistent brain alterations in humans. As an index of cannabinoid action, visual scanning, along with other attentional functions, was chosen. Visual scanning undergoes a major maturation process around age 12–15 years and, in addition, the visual system is known to react specifically and sensitively to cannabinoids. Methods: From 250 individuals consuming cannabis regularly, 99 healthy pure cannabis users were selected. They were free of any other past or present drug abuse, or history of neuropsychiatric disease. After an interview, physical examination, analysis of routine laboratory parameters, plasma/urine analyses for drugs, and MMPI testing, users and respective controls were subjected to a computer-assisted attention test battery comprising visual scanning, alertness, divided attention, flexibility, and working memory. Results: Of the potential predictors of test performance within the user group, including present age, age of onset of cannabis use, degree of acute intoxication (THC+THCOH plasma levels), and cumulative toxicity (estimated total life dose), an early age of onset turned out to be the only predictor, predicting impaired reaction times exclusively in visual scanning. Early-onset users (onset before age 16; n = 48) showed a significant impairment in reaction times in this function, whereas late-onset users (onset after age 16; n = 51) did not differ from controls (n = 49). Conclusions: These data suggest that beginning cannabis use during early adolescence may lead to enduring effects on specific attentional functions in adulthood. Apparently, vulnerable periods during brain development exist that are subject to persistent alterations by interfering exogenous cannabinoids.

Semi-quantitative analysis of cytokine gene expression in blood and cerebrospinal fluid cells by reverse transcriptase polymerase chain reaction

An easy, reproducible and semi-quantitative, non-radioactive method for the analysis of mRNA expression for various cytokines, (i.e., Interleukin (IL)-1β, IL-4, IL-6, tumor necrosis factor (TNF)-α, lymphotoxin (LT), transforming growth factor (TGF)-β, interferon (IFN)-γ and endothelin-1 (ET-1)) in cells from cerebrospinal fluid (CSF) and peripheral blood mononuclear cells (PBMC) has been established. By means of polymerase chain reaction primers that cover a splice junction, amplification of contaminating DNA was omitted. Densitometric scanning of ethidium bromide-stained agarose gels proved to be very sensitive for semiquantitative analysis of PCR products. Serial tenfold dilutions of cDNA revealed a log-linear regression from 106 to 102 cells under optimal cycle conditions. The intra- and inter-assay variability of the method was below 10%. With this assay, the cytokine expression pattern of as few as 104 mononuclear cells from blood or CSF was determined. This method made it possible to detect differences in the cytokine gene expression pattern of mononuclear cells from patients with different neurological diseases. CSF cells from 43 patients with various neurological diseases were analyzed. TNF-α, LT, and IL-1 mRNA were prominent in the CSF cells of most patients with bacterial meningitis. TNF-α, LT, IFN-γ and IL-6 mRNAs were detected in patients with active multiple sclerosis, whereas TNF-α, IL-6, and endothelin-1 mRNA expression was found frequently in patients with HIV encephalitis. Pro-inflammatory cytokines were rarely detected in CSF cells from patients with non-inflammatory diseases of the central nervous system. In blood mononuclear cells from patients with multiple sclerosis, TNF-α mRNA expression was associated with disease activity. The sensitivity, specificity, velocity and reliability of this assay considerably facilitates the analysis of cytokine production in mononuclear cells even in conditions where only a limited number of cells is available for analysis.

Differential Glial and Vascular Expression of Endothelins and Their Receptors in Rat Brain after Neurotrauma

We characterized the time-course, intensity of expression and cellular origin of components of the endothelin (ET) system in the rat brain after a standardized neurotrauma (cryogenic lesion of the parietal cortex). ET mRNAs were expressed at sham level after neurotrauma, whereas immunoreactivity for ET-1 was enhanced in glia and endothelium of the lesioned hemisphere and both hippocampi. The number of ET-3 positive mononuclear cells in the lesion perimeter increased starting at 24h after injury. At 48h after neurotrauma, ET-receptor immunoreactivity was increased in astrocytes. In basilar artery endothelium, ETB-immunoreactivity was reduced at 48h to 72h recovering at 7 days whereas ETA-receptor and ET-peptide immunoreactivities were not altered. In summary, neurotrauma leads to a multicellular stimulation of endothelins in the brain along with a delayed selective loss of vascular ETB-receptors. These changes seem to be posttranscriptional and cell type specific. They favor vasoconstriction increasing the risk of late vasospasm and ischemia.

OLITA : AN ALTERNATIVE IN THE TREATMENT OF THERAPY-RESISTANT CHRONIC ALCOHOLICS : FIRST EVALUATION OF A NEW APPROACH

The Outpatient Long-term Intensive Therapy for Alcoholics (OLITA) is a four-step program of care for severely affected chronic alcoholics which, after inpatient detoxification, extends over a total of 2 years. High-frequency short-term individual therapeutic contacts, initially daily, are followed by a slow tapering of individual contact frequency and resolve in a group session once weekly towards the end of the second abstinent year. Further elements of OLITA are: (a) induction of alcohol intolerance by the application of aldehyde dehydrogenase inhibitors; (b) introduction of control factors, i.e. controlled intake of deterrent medication and regular urine analysis for alcohol; and (c) allocation of responsibility to the patient with respect to the overall success of the therapeutic concept including his own physical rehabilitation. Thus far, 30 male alcoholic patients from two recruitment periods have been treated for 6–26 months with a success rate of 60% abstinent patients. In conclusion, OLITA, based on the gradual tapering of high-frequency therapeutic contacts, thus far unique among outpatient programs for alcoholics, represents a promising advance in the treatment of therapy-resistant chronic alcoholics.

Diffusion tensor imaging for long-term follow-up of corticospinal tract degeneration in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a predominantly clinical and electromyographic diagnosis. Conventional MRI reveals atrophy of the motor system, particularly the pyramidal tract, in the advanced stages but does not provide a sensitive measure of disease progression. Three patients with different principal symptoms of ALS, i.e., with predominant involvement of the upper (UMN) or lower (UMN) motor neurons, or bulbar disease, respectively, underwent serial clinical examination including lung function tests, conventional MRI, and diffusion tensor imaging (DTI). MRI demonstrated changes in of the pyramidal tract without measurable variation on follow-up. The patient with UMN involvement showed remarkable progressive loss of diffusion anisotropy in the pyramidal tract. DTI might be useful, together with clinical follow-up, as an objective morphological marker in therapeutic trials.

Role of the astrocytic ETB receptor in the regulation of extracellular endothelin‐1 during hypoxia

Astrocytes are known to possess an effective endothelin (ET) eliminatory system which involves astrocytic ETA and ETB receptors and may become particularly relevant under pathophysiological conditions. The present study has therefore been designed to explore the effect of standardized hypoxia on extracellular concentrations of endothelin‐1 (ET‐1) and on endothelin‐converting enzyme (ECE) activity in primary rat astrocytes genetically (sl/sl) or experimentally (dexamethasone) deficient in ETB receptors. The results revealed (1) a hypoxia‐mediated decrease of extracellular ET‐1 in wildtype astrocytes (+/+) that was not observed in ETB‐deficient (sl/sl) cultures; (2) an ET receptor antagonist‐induced increase in ET‐1 in the media of both genotypes with further elevation upon hypoxia in +/+ cultures only; (3) augmentation of the dexamethasone‐induced increase in extracellular ET‐1 by hypoxia in +/+, but not in sl/sl cultures; (4) synergistic reduction of ETB gene transcription by hypoxia and dexamethasone; and (5) significant increases in endothelin‐converting enzyme activity in the presence of hypoxia. To conclude, hypoxia stimulates astrocytic release of mature ET‐1. This stimulation is (over)compensated for by increased ET‐1 binding to functional ETB receptors. ETB deficiency, whether genetic or experimentally induced, impairs elimination of extracellular ET‐1. GLIA 34:18–26, 2001.

Endothelin B receptor-deficient rats as a subtraction model to study the cerebral endothelin system.

Endothelins, due to their potent vasoactivity and mitogenicity, appear to play an important role in the brain, where all components of the endothelin system, peptides, receptors and converting enzyme, are expressed. To further elucidate the role of the cerebral endothelin system, astrocytes and cerebral vessels from sl/sl rats, devoid of functional endothelin B receptors, have been employed. Astrocytes from sl/sl rats display the following abnormalities as compared to wild-type (+/+) cells: (i) elevated basal extracellular endothelin-1 levels; (ii) exclusive presence of functional endothelin A receptors; (iii) increased extracellular endothelin-1 levels upon endothelin A receptor blockade; (iv) augmented basal endothelin-converting enzyme activity; (v) altered calcium response to endothelin-1. The basilar artery of sl/sl rats shows an enhanced constricting response to endothelin-1 and fails to dilate in response to endothelin-3, shifting the endothelin vasomotor balance to constriction. In conclusion, endothelin B receptors may be essential for restricting extracellular endothelin-1 levels in the brain, as well as for a balanced cerebral vasomotor action of endothelins.

ENDOTHELIUM-DEPENDENT RELAXATION COUNTERACTING THE CONTRACTILE ACTION OF ENDOTHELIN-1 IS PARTLY DUE TO ETB RECEPTOR ACTIVATION

The vasomotor effects of the endothelins (ETs) are mediated by activation of receptor subtypes termed ETA and ETB. The present study aimed to characterize the interaction of ETA and ETB receptor activation in the cerebral circulation. Ring segments obtained from rat basilar artery were used for measurement of isometric force under resting tension or following precontraction with prostaglandin F2α. In some segments, the endothelium was removed mechanically. In precontracted arteries, ET-1 elicited contraction only. In the presence of the ETA receptor antagonist, BQ-123 (10−5 M), however, ET-1 induced a concentration-related relaxation with a pD2 value of 8.93±0.16 (mean±SEM,n=15). The relaxant action was abolished following princubation with an ETB receptor antagonist, IRL-1038 (3×10−6 M), or with a nitric oxide synthase inhibitor,NG-nitro-l-arginine (10−5 M). These results indicate that the relaxation was mediated by ETB receptor activation coupled to the release of nitric oxide. Under resting tension, ET-1 elicited concentration-related contraction (pD2: 8.03±0.04,n=37). In arteries devoid of a functional endothelium, the concentration-effect curve was shifted to the left yielding a pD2 value of 8.88±0.11 (n=31). Similarly, in endotheliumintact arteries contraction to ET-1 was augmented following nitric oxide synthase inhibition or ETB receptor blockade with 3×10−6 M BQ-788 (pD2: 8.94±0.18,n=19). The results suggested that, in the isolated rat basilar artery, ET-1 induced coactivation of the contraction-mediating ETA receptor and the relaxation-mediating ETB receptor. The coactivation resulted in opposing vasomotor effects, but the contraction covered relaxation under normal conditions. However, force development by ET-1 was suppressed by its endothelium-dependent relaxant action.

A novelty-related sustained elevation of vasopressin plasma levels in young men is not associated with an enhanced response of adrenocorticotropic hormone (ACTH) to human corticotropin releasing factor (hCRF)

A comparative study of the effects of intravenously administered corticotropin releasing factor (i.e. exogenous CRF), in the absence or presence of simultaneous opioid receptor blockade, versus stress (i.e., endogenous CRF) on plasma adrenocorticotropic hormone (ACTH), cortisol and vasopressin (AVP) was carried out in ten healthy men (mean age 35.6±9.5 years) using an intra-individual repeat setting. Three different stimuli were applied blindly and in random order, one per day, in a 3-day experimental block: (1) human (h)CRF; (2) hCRF/naloxone; and (3) a combined multifaceted 5-min stress test. A second block, following the same protocol, was carried out 12 weeks later. Each experimental day lasted from 0700 to 1500 hours, with subjects remaining supine throughout. ACTH and cortisol levels each responded with significant peaks to all three stimulating conditions in both blocks while AVP levels remained unaffected by any of these stimuli. Unexpectedly, in five of the ten subjects significantly elevated AVP basal concentrations were measured throughout the first block. This phenomenon appeared to be age-related, being observed in younger men only (29.6±5.2 vs 41.6±9.2 years;p=0.03) and was not paralleled by changes in plasma osmolality or blood pressure. In the second block, AVP levels were low and no longer different between younger and older subjects. ACTH and cortisol curves did not differ among subgroups nor between blocks. In conclusion, plasma AVP, in contrast to ACTH, is not acutely influenced by either endogenous or exogenous CRF. However, anticipation of novelty seems to be a human-specific, stress-related stimulus for a sustained elevation of plasma AVP in young men. This novelty-related continuous elevation of AVP levels reported here neither affected basal plasma ACTH nor acted synergistically with exogenous hCRF to increase circulating ACTH.

Loss of ETB-Receptor-Mediated Relaxation in Basilar Artery after Cold Lesion of the Rat Parietal Cortex

The endothelins (ETs) can exert both constrictor and dilator effects. These opposite actions have been attributed to the existence of different ET receptors. The ETA receptor has high affinity for ET-1 and ET-2 but low affinity for ET-3, while the ETB-receptor is non-selective in this respect. Stimulation of ETA receptors, which are located on vascular smooth muscle, causes vasoconstriction (Feger et al., 1994). This vasomotor reaction is mediated by activation of phospholipase C and protein kinase C (Gorlach et al., 1998a). ETB receptors of arteries mediate vasodilation which is coupled to NO-production in endothelial cells (Schilling et al., 1995).