High-affinity 3H-imipramine binding in platelets of children and adolescents with major affective disorders

High-affinity ³H-imipramine binding to platelet membranes was evaluated in 12 untreated children and adolescents aged 11–17 years who met the DSM-III criteria for major affective disorders. The affective patients were compared to 13 nonaffective subjects and 15 normal controls of similar ages. No significant difference in the maximal binding of ³H-imipramine (B_max) and K_d values could be found among the three groups. ³H-imipramine binding values failed to discriminate between patients with major depression and those with bipolar disorder, depressed type. No association between a positive family history of major affective disorders and ³H-imipramine binding values was detected.     

Variability in D2-dopamine receptor density and affinity: A PET study with [11C]raclopride in man

The variability of D₂-dopamine receptor binding parameters in man was determined using Positron Emission Tomography (PET) and [¹¹C]raclopride. A saturation analysis based on five PET-experiments was performed in each of ten men and ten women. The mean density of D₂-dopamine receptors (B_max) was 28 ± 6.9 pmol/ml (mean ± S.D.) and the apparent affinity (K_d^app)9.1 ± 1.9 pmol/ml. The Hill coefficient was in all subjects close to unity (n_H: 0.999 ± 0.020), thereby indicating binding to a homogeneous class of receptors. No significant differences between males and females were found in B_max or K_d^app. The interindividual difference in B_maxwas statistically significant (α = 0.01). The difference in K_d^app was not significant. Upregulation of the receptor density (B_max) has been widely discussed as a mechanism for increased dopaminergic neurotransmission in schizophrenia. This study indicates that receptor density varies considerably in a group of healthy subjects. © 1995 Wiley-Liss, Inc.     

The effects of loss versus alteration of consciousness on inhibition-related brain activity among individuals with a history of blast-related concussion

Paroxetine binding could be a vulnerability marker for traits associated with borderline personality disorder (BPD). To study this relationship, we examined [³H] paroxetine binding in female patients with BPD and their sisters. The sample consisted of 54 sibling pairs in which a proband met criteria for BPD. All subjects were given the Diagnostic Interview for Borderlines, revised (DIB-R), the Diagnostic Assessment for Personality Pathology: Brief Questionnaire (DAPP-BQ), the Barratt Impulsivity Scale (BIS), the Affective Lability Scale (ALS), the Hamilton Rating Scale for Anxiety (HAM-A), the Hamilton Rating Scale for Depression (HAM-D), and the Symptom Checklist-90, revised (SCL-90-R). All subjects had platelets assayed for [³H] paroxetine binding. There were no significant differences between probands and sisters, but both groups scored significantly lower than a previously studied control group on B_max. There were no differences on Kd. Neither B_max nor K_d was related to most trait or symptomatic measures. Paroxetine binding could reflect endophenotypes common to BPD probands and their first-degree relatives.     

Temperature and Protein Kinase C Modulation of Gonadotropin-Releasing Hormone Receptors in Pituitary Cells from Intact or Castrated Male Rats

Binding constants of [¹²⁵ I]Des-Gly₁₀-(D-Ala₆)-gonadotropin-releasing hormone-ethylamide (GnRHa) to dispersed pituitary cells were evaluated in a 4-day culture. Cells were sampled either from intact or from castrated male rats and binding was measured at various temperatures before or after treatment with phorbol-12-myristate-13-acetate (PMA) or 1-5-(isoquinolinyl-sulfoxyl) 2-methylpiperazine (H7), which activate or inhibit, respectively, protein kinase C (PKC). In cells from intact rats incubated with increasing concentrations of ligand at 21 °C for 25 min, the Scatchard plot was not linear and calculation of the Hill coefficient (N_H) was indicative of positive cooperativity (N_H= 1.26 ± 0.02). Such non-linearity was not observed when cells were incubated at 0.5 °C for 3 h. In that condition the maximal number of binding sites measured at equilibrium (B_max) increased (15.1 ± 0.05 versus 9.3 ± 0.5 fmoles × mg^?1 proteins at 21 °C). Two control experiments permitted us to rule out the possibility that lower B_max at 21 °C might reflect internalization: 1) Cells were first incubated with the ligand at 21 °C for 25 min and subsequently for 3 additional hours at 0.5 °C. Preincubation did not affect the B_max obtained at 0.5 °C; 2) when the radioligand bound to the cell surface was washed out with an acidic buffer, only 13% of the specific radioactivity was retained irrespective of the ligand concentration applied, a much lower value than the 40% binding difference observed between 0.5°C and 21°C. When the cells were incubated with PMA, the Scatchard plot was linearized and the B_max recorded at 21 °C increased by 50% over control cells (13 ± 0.7 fmoles × mg^?1 proteins). Conversely, inhibition of PKC by H7, a preferential PKC inhibitor, was ineffective. In contrast, cells sampled from castrates exhibited linear and comparable Scatchard plots at either 0.5 ° or 21 °C, with B_max values of 14.4 ± 0.3 and 15 ± 0.34 fmoles × mg^?1 proteins, respectively. PKC activation did not affect binding in that model, but H7 decreased the number of sites (B_max= 10.7 ± 0.9) and induced appearance of positive cooperativity (N_H= 1.36 ± 0.07). Taken together, these experiments reveal a pool of GnRH receptors in the pituitary of intact rats that recognizes the ligand in a phosphorylation-dependent manner. These binding sites also became evident when biological properties of the membrane were modified by temperature or cell homogenization. After castration, PKC activation was no longer a prerequisite for recruitment of the total population of receptors whereas protein kinase inhibition resulted in a reduction of maximal binding. Finally, our observations demonstrate that GnRH binding can exhibit positive cooperativity, either on normal cells or on cells from castrates after protein kinase inhibition, suggesting that such a cooperativity is not related to a GnRH-dependent phosphorylation.     

Platelet imipramine binding and serotonin uptake in obsessive-compulsive patients

Platelet imipramine binding was measured in 16 drug-free nondepressed patients (aged 20-61 years, mean ± SD 35 ± 8) suffering from obsessive-compulsive disorder (OCD) and in 16 sex-, race- and age-matched healthy controls. Imipramine binding capacity and affinity were not different in the 2 groups. Platelet serotonin (5-HT) uptake capacity, V_max, was also measured in 15 of these patients and their matched controls. V_max was significantly higher in the patients (309 ± 149 pmol/10⁹ cells/min) than in the controls (181 ± 110). An increase in platelet 5-HT uptake supports the involvement of 5-HT in OCD and may suggest that a hyperactive serotonergic system is present in this disorder.     

Binding characteristics of the glucocorticoid receptor in peripheral blood lymphocytes in multiple sclerosis

Although the exact etiology of multiple sclerosis (MS) remains unresolved, immune reactions are believed to be the central pathogenic mechanisms. Endogenous and therapeutic steroid hormones affect the immune system, and inflammatory diseases are associated with activation of the hypothalamic-pituitary-adrenal axis, providing evidence of an immune-endocrine interplay. Function tests in MS have revealed dysregulation of the hypothalamic-pituitary-adrenal system in a substantial proportion of patients. We characterized glucocorticoid receptor (GR) binding in peripheral blood lymphocytes from 39 MS patients and 14 age- and sex-matched controls with respect to dissociation constant and binding capacity, using a whole-cell binding assay with [³H]dexamethasone as the ligand. GR binding parameters did not differ significantly between patients (K _d 8.98 ± 1.07 nM, B _max 183 ± 29.8 fmol/mg) and controls (K _d 9.36 ± 1.17 nM, B _max 158 ± 16 fmol/mg). No effect of age, sex, course, duration or severity of disease, or prior steroid treatments was detected. GR binding parameters were analyzed in relation to the results of the combined dexamethasone-CRH test, which reflects corticosteroid receptor function at the hypothalamus, in 30 patients and 9 controls. While controls showed a moderate correlation between binding affinity of the GR in lymphocytes and regulatory function at the hypothalamic level, the patients did not. These data suggest that the physiological relationship between binding and function of the glucocorticoid receptor is disturbed in MS. Received: 23 December 1997 Received in revised form: 12 August 1998 Accepted: 18 August 1998     

Subsensitivity of serotonin and substance P receptors involved in nociception after repeated administration of a serotonin receptor agonist

Summary In post-mortem putamen samples from 27 schizophrenics and 27 controls D₂ receptors were measured by Scatchard analysis using³H-spiperone as a ligand. Maximum number of binding sites (B_max) and apparent dissociation constant (K_D) were significantly increased only in patients in whom neuroleptic medication had been given within a three-month period before death. When the neuroleptic medication had been withdrawn at least 3 month before death, there was a slight, but not significant, reduction in B_max values and unchanged K_D values. Withdrawal of neuroleptic drugs was followed by a normalization of the K_D values within 2 weeks and a slower reduction of B_max values. There were 6 schizophrenic patients with mainly positive schizophrenic symptoms and 17 patients with mainly negative symptoms; positive schizophrenic symptoms were not related to higher B_max values. There was no difference in³H-spiperone binding between patients with and without movement disorders (tardive dyskinesia or extrapyramidal symptoms).     

Effect of injury on the bi-affinity α1-adrenoreceptor binding in rat brain in vivo

Focal freezing lesions in rats cause a widespread decrease of cortical glucose utilization in the lesioned hemisphere, probably as a reflection of depressed cortical activity. The noradrenergic neurotransmitter system was implicated in these alterations when it was demonstrated that prazosin, a specific norepinephrine (NE) antagonist at β₁-adrenergic receptors, prevented their development. In normal rat brain, specific binding of [¹²⁵I]HEAT [(±)2-(3-[¹²⁵I]iodo-4-hydroxyphenyl)-ethyl-aminomethyltetralone], another selective α₁-adrenoreceptor ligand, was demonstrated in vivo at sites consistent with the α_1A- and α_1B-adrenoreceptor subtypes. In the present study, the effect of a freezing lesion on specific binding of [¹²⁵I]HEAT in rat brain in vivo was determined three days after traumatization when cortical glucose use suggested the greatest degree of functional depression. The steady-state volumes of distribution of [¹²⁵I]HEAT three days after injury were significantly increased in all the cortical areas of the lesioned hemisphere, but not in the subcortical structures. Injury did not modify the binding affinities for HEAT. However, a statistically significant increase in the number of low-affinity binding sites for this ligand was demonstrated in all cortical areas of the lesioned hemisphere, but not in subcortical structures. The traumatization did not modify B_max. estimates for the high-affinity binding of HEAT. The results support the hypothesis that changes in the noradrenergic system are of functional importance in brain injury and that at least some effects of injury are mediated by α_1B-adrenergic receptors. © 1995 Wiley-Liss, Inc.     

Striatal binding of11C-NMSP studied with positron emission tomography in patients with persistent tardive dyskinesia: no evidence for altered dopamine D2 receptor binding

Summary Dopamine D₂ receptor binding characteristics were studied by positron emission tomography (PET) using N-¹¹C-methyl spiperone as receptor ligand in patients on longterm treatment with neuroleptic drugs and in control subjects. Eight of the patients had symptoms of tardive dyskinesia whereas three patients did not have any symptoms. Control subjects comprised 5 healthy volunteers and 7 patients with pituitary tumors. All patients had been free of neuroleptic drugs for at least 4 weeks. The time dependent regional radioactivity in the striatum was measured and the receptor binding rate, k₃, proportional to receptor number, B_max and association rate for the receptor was calculated in relation to the cerebellum. The lack in difference in k₃ values between TD patients, neuroleptic treated patients without TD and control subjects throws doubt on the hypothesis that changes in striatal D₂ dopamin receptor number or binding affinity is an etiological mechanism for persistent TD.     

Serotonergic measures in suicide brain: 5-HT1A binding sites in frontal cortex of suicide victims

Summary The density of 5-HT_1A binding using³H-8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) as binding ligand, was studied in human frontal cortex of suicide victims and normal controls who died due to medical disease or accidentally. There was no difference in the maximum number of binding site (B_max) or K_d (an inverse measure of affinity) of 5-HT_1A receptor binding sites between normal controls and the entire group of suicide victims. However, nonviolent suicides had significantly higher B_max (22—25%) compared to both controls and violent suicides. A negative correlation between age and B_max of 5-HT_1A binding sites was found in male controls but not in female controls or suicide victims. This relationship was less apparent among the male controls over age 60.