Anna Wägner

Lower 3H-imipramine binding in platelets from untreated depressed patients compared to healthy controls

3H-Imipramine binding in platelets was measured in 63 severely depressed hospitalized patients, who had been drug free (with the exception of moderate doses of benzodiazepines) for at least 1 month, and in 53 healthy control subjects of comparable age and sex distribution. Bmax of 3H-imipramine binding was significantly lower in the depressed subjects (1012 +/- SD 295 vs. 1123 +/- SD 178 fmole/mg protein). Depressed patients who had attempted suicide by violent means tended to have higher Bmax than nonviolent attempters.

Regional cerebral blood flow as assessed by principal component analysis and 99m Tc-HMPAO SPET in healthy subjects at rest: normal distribution and effect of age and gender

Abstract. The increasing implementation of standardisation techniques in brain research and clinical diagnosis has highlighted the importance of reliable baseline data from normal control subjects for inter-subject analysis. In this context, knowledge of the regional cerebral blood flow (rCBF) distribution in normal ageing is a factor of the utmost importance. In the present study, rCBF was investigated in 50 healthy volunteers (25 men, 25 women), aged 31–78 years, who were examined at rest by means of single-photon emission tomography (SPET) using technetium-99m d,l-hexamethylpropylene amine oxime (HMPAO). After normalising the CBF data, 27 left and 27 right volumes of interest (VOIs) were selected and automatically outlined by standardisation software (computerised brain atlas). The heavy load of flow data thus obtained was reduced in number and grouped in factors by means of principal component analysis (PCA). PCA extracted 12 components explaining 81% of the variance and including the vast majority of cortical and subcortical regions. Analysis of variance and regression analyses were performed for rCBF, age and gender before PCA was applied and subsequently for each single extracted factor. There was a significantly higher CBF on the right side than on the left side (P<0.001). In the overall analysis, a significant decrease was found in CBF (P=0.05) with increasing age, and this decrease was particularly evident in the left hemisphere (P=0.006). When gender was specifically analysed, CBF was found to decrease significantly with increasing age in females (P=0.037) but not in males. Furthermore, a significant decrease in rCBF with increasing age was found in the brain vertex (P=0.05), left frontotemporal cortex (P=0.012) and temporocingulate cortex (P=0.003). By contrast, relative rCBF in central structures increased with age (P=0.001). The ability of standardisation software and PCA to identify functionally connected brain regions might contribute to a better understanding of the relationships between rCBF at rest, anatomically defined brain structures, ageing and gender.

Effects of fluoxetine treatment of platelet 3H-imipramine binding, 5-HT uptake and 5-HT content in major depressive disorder

Platelet 3H-imipramine binding, serotonin (5-HT) uptake and 5-HT concentrations were studied in 14 hospitalized patients with depressive disorder following 6 weeks of treatment with a selective 5-HT uptake blocker, fluoxetine. After 3 weeks of treatment there was a significant decrease in Bmax of 3H-imipramine binding and a significant increase in Kd. A highly significant decrease in Vmax of 5-HT uptake was seen after 3 weeks of treatment which was accompanied by a slight increase in Km. At the same time the platelet 5-HT content was significantly reduced by about 90% of its original level. The platelet 5-HT content continued to decrease with further treatment while there was a tendency for Vmax to return to pretreatment levels. The affinity of the 5-HT uptake carrier continued to decrease significantly. There was no further significant change in Bmax of 3H-imipramine binding during further treatment, although there was an increase in Bmax in the majority of patients. The changes in Bmax and Vmax were closely associated throughout the treatment. In some cases the changes in different platelet parameters correlated with the changes in depression rating scores during treatment, but this correlation did not reach statistical significance.

Effects of clomipramine treatment on cerebrospinal fluid monoamine metabolites and platelet 3 H‐imipramine binding and serotonin uptake and concentration in major depressive disorder

In an open study of 12 inpatients who met the DSM‐III criteria for a major depressive episode, the effects of clomipramine (CI) on the monoamine metabolites 5‐hydroxyindoleacetic acid (5‐HIAA), homovanillic acid (HVA), 4‐hydroxy‐3‐methoxyphenyl glycol (HMPG) in cerebrospinal fluid (CSF) were measured simultaneously with the effects on 3H‐imipramine binding, serotonin (5‐HT) uptake and 5‐HT concentration in platelets after 3 and 6 weeks of treatment. Drug (CI and desmethylclomipramine) plasma concentrations were determined. The concentrations of 5‐HIAA and HMPG decreased substantially, and the concentration of HVA remained unchanged. There was also a large and significant reduction of the number of imipramine binding sites (Bmax and of the platelet 5‐HT concentration. The 5‐HT uptake was not measurable after 3 weeks of treatment. None of the parameters changed significantly between weeks 3 and 6. There were no significant correlations between antidepressant effect (measured by the Montgomery‐Åsberg Depression Rating Scale) and plasma drug concentrations, although a tendency to a significant correlation between antidepressant effect and CI was observed at 3 weeks. There were no significant intercorrelations between the different 5‐HT parameters and no other significant correlations between the biochemical measures and clinical outcome.

Extradural Compression of Sensorimotor Cortex: A Useful Model for Studies on Ischemic Brain Damage and Neuroprotection

Behavioral and morphological changes were examined for up to 9 days after moderate cerebral ischemia caused by slow compression of a specific brain area in the sensorimotor cortex of Sprague-Dawley rats. Functional deficits after the cerebral ischemia were assessed by daily beam-walking tests, whereas morphological changes were verified using Nissl staining on day 1, 2, 3, 5, and 9, respectively. Rats exposed to cerebral ischemia displayed impaired beam walking performance. Mild hypothermia prevented both the compression-produced functional deficits and the brain damage. Younger (5 weeks) animals showed less neurological deficits than older (9 weeks) animals. Histological examination revealed a pronounced increase in the number of injured pyramidal neurons from day 1 to day 3 in the primarily damaged brain region. Between day 3 and day 5, the number of injured cells remained constant, whereafter there was a slow decline of thionin-positive neurons as examined on day 9. The noncompetitive NMDA receptor antagonist, dizocilpine (MK-801; 3 mg/kg, i.p.), did not alter the neurological impairment on day 1, but improved thereafter the rate of functional recovery and reduced the number of damaged cells. The AMPA receptor antagonist, LY326325 (15 or 30 mg/kg; i.p.), dose-dependently diminished the neurological deficits on day 1, enhanced the rate of recovery, and reduced the number of injured neurons over time. Our data suggest that short-lasting extradural compression of a well-defined brain area in the sensorimotor cortex is a highly reproducible model with a high success rate for the study of functional and morphological consequences after cerebral ischemia as well as for the evaluation of the therapeutic potential of novel, neuroprotective pharmacological agents.

Prolonged inhibition of glutamate reuptake down-regulates NMDA receptor functions in cultured cerebellar granule cells.

Abstract: In the present study, we have examined the effects of prolonged (up to 72 h) inhibition of high‐affinity glutamate reuptake by L‐trans‐pyrrolidine‐2,4‐dicarboxylate (PDC; 100 γM) on glutamate receptor functions in primary cultures of rat cerebellar granule neurons. This was done by comparing the effects of various glutamate receptor agonists on neuronal 45Ca2+ uptake, free cytoplasmic Ca2+ concentration ([Ca2+]i), and cell viability. We also determined the parameters of [3H]MK‐801 binding as well as the expression of the NMDAR1 subunit protein in control and PDC‐exposed cultures. The blockade of glutamate reuptake by PDC led to a gradual increase of ambient glutamate to concentrations that are neurotoxic when applied acutely to control cells. In PDC‐exposed cells, however, the acute glutamate‐induced NMDA receptor‐mediated calcium fluxes were strongly diminished and no toxicity was observed. The down‐regulation of the functional effects of glutamate was dependent on the duration of PDC exposure and was accompanied by a reduced NMDAR1 subunit expression and decreased [3H]MK‐801 binding, indicative of a pronounced structural rearrangement of NMDA receptors. The possibility that the decrease of NMDA glutamate receptor sensitivity can be explained on the basis of a reduced density or altered subunit composition of NMDA receptors is discussed.

Mapping pathological (99m)Tc-d,l-hexamethylpropylene amine oxime uptake in Alzheimer's disease and frontal lobe dementia with SPECT.

Seventeen patients with probable Alzheimer’s disease (AD), 7 patients with frontal lobe dementia (FLD) and 19 control subjects (NOR) were examined by 99mTc-d,l- hexamethylpropylene amine oxime (99mTc-HMPAO) SPECT. Images were standardised in the same 3D space and averaged within each group. After normalisation, the three sets of images were analysed in all cerebral lobes, hippocampus, thalamus and basal ganglia. In AD, the 99mTc-HMPAO uptake values were significantly reduced, as compared to NOR, in the parietal, temporal and insular lobes. In patients with FLD, the uptake was altered in all lobes with the exception of the parietal lobe. The uptake in the nucleus caudatus decreased significantly in both AD and FLD as compared to NOR. The uptake in the anterior cingulate cortex was significantly reduced in FLD. Subtraction images highlighted all significantly decreased areas. In conclusion, standardising SPECT in a common space and subtracting data from a control group improves the visual interpretation of images. In this study, the typical temporo-parietal and fronto-parietal 99mTc-HMPAO uptake reductions were found in AD and FLD, respectively. The uptake in the nucleus caudatus was found to decrease significantly in AD and FLD and the one in the anterior cingulate cortex was reduced in FLD.

Antagonist, CP-101,606, Enhances the Functional Recovery The NMDA NR2B Subunit-Selective Receptor and Reduces Brain Damage after Cortical Compression-Induced Brain Ischemia

Using a novel in vivo model for cerebral ischemia produced by short-lasting compression of a well-defined brain area of sensorimotor cortex we studied neuroprotective effects of the NMDA NR2B subunit selective antagonist, CP-101,606, in Sprague-Dawley rats. Cortical compression for 30 min produced a consistent and highly reproducible functional impairment, that is paresis of contralateral hind and fore limbs. The neurological deficit was accompanied by marked brain damage in cerebral cortex, hippocampus and thalamus as identified by Fluoro-Jade, a marker of general neuronal cell death. Using a daily performed beam walking test it was shown that untreated animals recovered from their functional impairment within 5-7 days following surgery. Intravenous administration of increasing doses (1, 5, 10, 20 mg/kg) of the NMDA NR2B subunit receptor specific antagonist, CP-101,606, dose-dependently improved the rate of functional recovery and protected against the ischemic brain damage in cerebral cortex, hippocampus, and thalamus as identified 2 days after the ischemic insult. Based upon these results, we conclude that NMDA NR2B receptor subunits represent potential targets to reduce not only the functional deficits, but also neuronal death in cortex and several midbrain regions produced by moderate, transient, cerebral ischemia.

Weak binding of 10-hydroxymetabolites of nortriptyline to rat brain muscarinic acetylcholine receptors

The relative affinities of nortriptyline (NT) and its 10-hydroxymetabolites to rat brain muscarinic acetylcholine receptors have been determined by competition with 3H-quinuclidinyl benzilate binding. It is shown that the major NT metabolite, E-10-OH-NT, has only 1/18 the affinity of NT for the muscarinic receptor. Since this metabolite is equipotent to NT in inhibiting neuronal noradrenaline uptake, it is suggested that it might be of clinical value as an antidepressant by virtue of having less anticholinergic side-effects than NT itself.

Circadian variation of platelet 3H-imipramine binding, platelet serotonin content, and plasma cortisol in healthy volunteers

Platelet 3H-imipramine binding, platelet serotonin content, and plasma cortisol were measured in 10 healthy female volunteers. Samples were taken on 5 occasions with a 6-hr interval during a 24-hr period within 1 week in May. Although there were individual variations in the biochemical parameters over a 24-hr period, we could not establish a clear common circadian rhythm for all subjects in platelet 3H-imipramine binding and platelet serotonin concentrations. During the night, there was a significant decrease in Bmax values and a slight, but not significant, increase in serotonin concentrations. A distinct circadian rhythm was obtained for plasma cortisol, with lowest values during the night.