Decreased platelet 3H-paroxetine binding in obsessive-compulsive patients

A long and winding road: My personal journey to oxytocin with no return

The present paper is the personal narration of the author reviewing her scientific pathways that led her toward the study of oxytocin. My work began with a pioneering study showing a decreased number of the serotonin transporter proteins in romantic lovers. This unexpected finding promoted my interest in the neurobiology of human emotions and feelings, and significantly shifted my research focus from diseases to physiological states that underlie "love." During this time increasing experimental data broadened the spectrum of activities of oxytocin from female functions, such as parturition and lactation, to modulation of the stress and immune system. The literature also began to reveal an important role for oxytocin in a sense of safety and wellbeing, processes that are critical to both love and survival. I suggest here that future studies should disentangle different emerging questions regarding the exact role of oxytocin within human nature, as well as its possible therapeutic applications in different physiological conditions and pathological states. Understanding these, in turn, holds the potential to improve the lives of both individuals and societies.

Is there a relationship between morphological and functional platelet changes and depressive disorder?

BACKGROUND

Blood platelets, due to shared biochemical and functional properties with presynaptic serotonergic neurons, constituted, over the years, an attractive peripheral biomarker of neuronal activity. Therefore, the literature strongly focused on the investigation of eventual structural and functional platelet abnormalities in neuropsychiatric disorders, particularly in depressive disorder. Given their impact in biological psychiatry, the goal of the present paper was to review and critically analyze studies exploring platelet activity, functionality, and morpho-structure in subjects with depressive disorder.

METHODS

According to the PRISMA guidelines, we performed a systematic review through the PubMed database up to March 2020 with the search terms: (1) platelets in depression [Title/Abstract]"; (2) "(platelets[Title]) AND depressive disorder[Title/Abstract]"; (3) "(Platelet[Title]) AND major depressive disorder[Title]"; (4) (platelets[Title]) AND depressed[Title]"; (5) (platelets[Title]) AND depressive episode[Title]"; (6) (platelets[Title]) AND major depression[Title]"; (7) platelet activation in depression[All fields]"; and (8) platelet reactivity in depression[All fields]."

RESULTS

After a detailed screening analysis and the application of specific selection criteria, we included in our review a total of 106 for qualitative synthesis. The studies were classified into various subparagraphs according to platelet characteristics analyzed: serotonergic system (5-HT2A receptors, SERT activity, and 5-HT content), adrenergic system, MAO activity, biomarkers of activation, responsivity, morphological changes, and other molecular pathways.

CONCLUSIONS

Despite the large amount of the literature examined, nonunivocal and, occasionally, conflicting results emerged. However, the findings on structural and metabolic alterations, modifications in the expression of specific proteins, changes in the aggregability, or in the responsivity to different pro-activating stimuli, may be suggestive of potential platelet dysfunctions in depressed subjects, which would result in a kind of hyperreactive state. This condition could potentially lead to an increased cardiovascular risk. In line with this hypothesis, we speculated that antidepressant treatments would seem to reduce this hyperreactivity while representing a potential tool for reducing cardiovascular risk in depressed patients and, maybe, in other neuropsychiatric conditions. However, the problem of the specificity of platelet biomarkers is still at issue and would deserve to be deepened in future studies.

The complex interactions among serotonin, insulin, leptin, and glycolipid metabolic parameters in human obesity

OBJECTIVE

To provide evidence to the link between serotonin (5-HT), energy metabolism, and the human obese phenotype, the present study investigated the binding and function of the platelet 5-HT transporter (SERT), in relation to circulating insulin, leptin, and glycolipid metabolic parameters.

METHODS

Seventy-four drug-free subjects were recruited on the basis of divergent body mass index (BMIs) (16.5-54.8 Kg/m2). All subjects were tested for their blood glycolipid profile together with platelet [3H]-paroxetine ([3H]-Par) binding and [3H]-5-HT reuptake measurements from April 1st to June 30th, 2019.

RESULTS

The [3H]-Par Bmax (fmol/mg proteins) was progressively reduced with increasing BMIs (P < .001), without changes in affinity. Moreover, Bmax was negatively correlated with BMI, waist/hip circumferences (W/HC), triglycerides (TD), glucose, insulin, and leptin, while positively with high-density lipoprotein (HDL) cholesterol (P < .01). The reduction of 5-HT uptake rate (Vmax, pmol/min/109 platelets) among BMI groups was not statistically significant, but Vmax negatively correlated with leptin and uptake affinity values (P < .05). Besides, [3H]-Par affinity values positively correlated with glycemia and TD, while [3H]-5-HT reuptake affinity with glycemia only (P < .05). Finally, these correlations were specific of obese subjects, while, from multiple linear-regression analysis conducted on all subjects, insulin (P = .006) resulting negatively related to Bmax independently from BMI.

CONCLUSIONS

Present findings suggest the presence of a possible alteration of insulin/5-HT/leptin axis in obesity, differentially impinging the density, function, and/or affinity of the platelet SERT, as a result of complex appetite/reward-related interactions between the brain, gut, pancreatic islets, and adipose tissue. Furthermore, they support the foremost cooperation of peptides and 5-HT in maintaining energy homeostasis.

Pharmacotherapeutic Strategies and New Targets in OCD

Effective pharmacological and psychotherapeutic treatments are well established for obsessive-compulsive disorder (OCD). Serotonin reuptake inhibitors (SRIs) are first-line treatment and are of benefit to about half of patients. Augmentation of SRI treatment with low-dose neuroleptics is an evidence-based second-line strategy. Specialty psychotherapy is also used as both first-line and second-line treatment and can benefit many. However, a substantial number of patients do not respond to these treatments. New alternatives are urgently needed. This review summarizes evidence for these established pharmacotherapeutic strategies, and for others that have been investigated in refractory disease but are not supported by the same level of evidence. We focus on three neurotransmitter systems in the brain: serotonin, dopamine, and glutamate. We summarize evidence from genetic, neuroimaging, animal model, and other lines of investigation that probe these three systems in patients with OCD. We also review recent work on predictors of response to current treatments. While many studies suggest abnormalities that may provide insight into the pathophysiology of the disorder, most studies have been small, and non-replication of reported findings has been common. Nevertheless, the gradual accrual of evidence for neurotransmitter dysregulation may in time lead the way to new pharmacological strategies.

Biological markers for anxiety disorders, OCD and PTSD: A consensus statement. Part II: Neurochemistry, neurophysiology and neurocognition

OBJECTIVE

Biomarkers are defined as anatomical, biochemical or physiological traits that are specific to certain disorders or syndromes. The objective of this paper is to summarise the current knowledge of biomarkers for anxiety disorders, obsessive-compulsive disorder (OCD) and posttraumatic stress disorder (PTSD).

METHODS

Findings in biomarker research were reviewed by a task force of international experts in the field, consisting of members of the World Federation of Societies for Biological Psychiatry Task Force on Biological Markers and of the European College of Neuropsychopharmacology Anxiety Disorders Research Network.

RESULTS

The present article (Part II) summarises findings on potential biomarkers in neurochemistry (neurotransmitters such as serotonin, norepinephrine, dopamine or GABA, neuropeptides such as cholecystokinin, neurokinins, atrial natriuretic peptide, or oxytocin, the HPA axis, neurotrophic factors such as NGF and BDNF, immunology and CO2 hypersensitivity), neurophysiology (EEG, heart rate variability) and neurocognition. The accompanying paper (Part I) focuses on neuroimaging and genetics.

CONCLUSIONS

Although at present, none of the putative biomarkers is sufficient and specific as a diagnostic tool, an abundance of high quality research has accumulated that should improve our understanding of the neurobiological causes of anxiety disorders, OCD and PTSD.

Serotonin transporter promoter polymorphism is associated with executive function impairments in patients with obsessive compulsive disorder

OBJECTIVE

In the present study, we investigate the association between the 5-HTTLPR polymorphism and executive functions in a sample of patients with obsessive compulsive disorder (OCD).

METHOD

A total of 98 unmedicated patients diagnosed with OCD according to DSM-IV criteria and 80 healthy controls were included in this study. The genotype frequencies of 5-HTTLPR polymorphism were compared in OCD and healthy control groups. The four subgroups of OCD and healthy control participants, determined according to having LaLa genotype (high expressing) or S- and/or Lg alleles (low expressing), were also compared using neuropsychological tests of executive functions.

RESULTS

The frequency of SLa genotype of 5-HTTLPR polymorphism was found to be higher in patients with OCD compared with healthy controls. The mean scores of conceptual level responses of the Wisconsin Card Sorting Test (WCST) were significantly lower in the OCD-high-expressing subgroup compared with the low-expressing control group. The mean scores of the number of moves of the Tower of London were found to be significantly higher in the OCD-high-expressing subgroup, compared with the high-expressing subgroup of healthy controls.

CONCLUSION

Our findings suggest that the high-expressing variant may be associated with lower performance on some abstraction and planning measures in OCD patients.

A link between oxytocin and serotonin in humans: supporting evidence from peripheral markers

Pharmacological studies indicate a functional interaction between the serotonergic and oxytocinergic systems. In particular, some selective serotonin (5-HT) reuptake inhibitors, such as citalopram and fluvoxamine, seem to exert part of their antidepressant effects through oxytocin (OT) release. Further, the administration of fenfluramine, a serotonergic agonist, to healthy subjects increases plasma OT levels. Interestingly, immunocytochemical and double-immunofluorescent techniques revealed a high degree of overlap between 5-HT transporter (SERT)-labeled fibers and OT-containing cells in the paraventricular and supraoptic nuclei of primate hypothalamus. These findings suggest that the influence of 5-HT on OT system might be mediated by SERT. In this study, we explored the possible existence of a link between OT and SERT in human subjects, by means of two peripheral markers, the platelet SERT, as measured by [³H]-paroxetine ([³H]-Par) binding, and plasma OT levels. As far as [³H]-Par binding parameters are concerned, the Bmax (mean ± SD, fmol/mg protein) was 1155 + 130 and the Kd (mean ± SD, nM) was 1.31 ± 0.61. The OT plasma levels (mean ± SD, pg/ml) were 1.14 ± 1.07. A significant and positive correlation was found between plasma OT levels and Kd values (correlation coefficient: r: 0.466, p = .038). This result represents the first evidence of an interaction between OT and SERT, as measured by [³H]-Par binding, at peripheral levels in humans. Given the several activities mediated by both OT and 5-HT, such a relationship might provide new perspectives and insights into psychiatric disorders and/or social relationship disturbances, as well as novel treatment strategies overcoming and/or integrating the serotonergic paradigm.

Effects of cognitive-behavioral therapy on Eating Disorders: neurotransmitter secretory response to treatment

The effects of cognitive-behavioral therapy (CBT) on central dopamine (DA), noradrenaline (NE) and serotonin (5-HT) secretion were studied in a group of 50 female inpatients, of which 14 suffered from anorexia nervosa restricted type (AN-R), 14 from anorexia nervosa bingeing-purging type (AN-BP), and 22 from bulimia nervosa (BN). The aim of the study was to see whether or not CBT modifies the secretion of central DA (blood homovanillic acid=HVA), NE (blood 3-methoxy-4-hydroxy-phenylglycol=MHPG) and the 5-HT transporter (as evaluated by the platelet paroxetine binding=[(3)H]-Par-binding), if the physical and psychological effects of CBT correlate with changes of the neurotransmitter secretion; and if the biological effects of CBT are linked to specific psychopathological aspect of the disorders. The treatment lasted 20 weeks. Body-mass Index, bingeing and purging, specific AN-BN psychopathological (EDE 12-OD), depression (Beck Inventory), anxiety (STAY Form-Y-1), impulsiveness (Barratt Impulsiveness Scale), self-esteem (Rosenberg Self-Biochemical Scale) and temperament (Temperament and Character Inventory, Cloninger Scale) were assessed at baseline and at the end of the treatment. CBT significantly improved the psychophysical aspects of the diseases. HVA and MHPG concentrations did not change. The [(3)H]-Par-binding parameters, the maximum binding capacity (B(max)) and dissociation constant (K(d)) values did not change in either AN-R or AN-BP patients, while the [(3)H]-Par B(max) (and not the K(d)) increased significantly in BN patients. Correlations emerged between basal and final [(3)H]-Par B(max) values and psychopathological scores, but not between CBT-induced differences between basal and final values. Our data suggest that only in BN CBT may act through changes in 5-HT system function.

Trazodone effects on [H]-paroxetine and alpha(2)-adrenoreceptors in platelets of patients with major depression

Trazodone is an antidepressant which behaves as a selective 5-HT(2) antagonist and 5-HT reuptake inhibitor. The lack of information on its effects in vivo prompted us to evaluate alpha(2)-adrenoceptors by means of the specific binding of [(3)H]-rauwolscine, and the 5-HT transporter (SERT) by means of the binding of [(3)H]-paroxetine ([(3)H]-Par), in platelets of depressed patients, before and after one month of treatment with trazodone (75-300 mg/day). Twenty-five outpatients of both sexes with a diagnosis of major depression, as assessed by the Structured Clinical Interview for DSM IV, were included in the study. Depressive symptoms were evaluated by means of the Hamilton Rating Scale for Depression: the total score (mean +/- SD) was 20 +/- 6 at baseline (t(0)) and 7 +/- 4 after one month of treatment (t(1)). Platelet membranes, [(3)H]- rauwolscine and [(3)H]-Par bindings were carried out according to standardized protocols. The results showed that the B(max) values of [(3)H]-Par were statistically lower at t(1) than at t(0) (733 +/- 30 vs 1471 +/- 99, P < 0.001), while the K(d) and the [(3)H]-rauwolscine binding parameters remained unchanged. The findings of this study suggest that in vivo trazodone modifies the number of the SERT proteins and that, perhaps, most of its antidepressant properties are related to this activity.

Male axillary extracts modify the affinity of the platelet serotonin transporter and impulsiveness in women

The presence of functional pheromones in axillary extracts in humans is still matter of debate. Scattered data suggest that unidentified human axillary compounds with pheromonal activity may influence mood and this may occur, perhaps, through the modulation of the serotonin (5-HT) system that has been linked to mood by several findings. Therefore, the aim of this study was to assess the possible changes of a peripheral marker of the 5-HT system, i.e., the platelet 5HT transporter, and of some psychological tests, in a group of women who were exposed to male axillary extracts (group 1). A matched group of women who underwent an exposure to a neutral solution, were used as control subjects (group 2). The 5-HT transporter was evaluated by means of the specific binding of (3)H-paroxetine ((3)H-Par) to platelet membranes, as well as by means of (3)H-5-HT reuptake in whole platelets, at baseline (T0) and 1h after the stimulation (T1). The following tests were used: the "Experiences in Close Relationships" questionnaire (ECR), the latest version of the Barratt Impulsiveness Scale (BIS-11) and the Structured Clinical Interview for Mood Spectrum, self-reported version. The dissociation constant (Kd) of (3)H-Par binding showed a significant decrease at T1 only in the women exposed to male axillary extracts, as compared with baseline values, while the Bmax and (3)H-5-HT reuptake parameters did not show any change in both groups. The correlation analyses showed that at T0, the Kd values correlated significantly and positively with the factor of motor impulsiveness in all subjects. Two factors of the BIS-11, in particular, the attentional and the motor impulsiveness were significantly lower at T1 in the group 1. Further, at T1 and still in the group 1, a significant and positive correlation was measured between the Kd values and two ECR attachment styles, the secure and preoccupied, as well as with the ECR anxiety scale. Taken together, these findings suggest that the application of male axillary extracts to women may modify the affinity of their platelet 5-HT transporter, as well as of some impulsiveness and romantic attachment characteristics. The substances responsible for this effect remain to be identified.

Normalisation of immune cell imbalance after pharmacological treatments of patients suffering from obsessive-compulsive disorder

Recent data have shown the presence of immunological alterations in adult patients suffering from obsessive-compulsive disorder (OCD). The objective of this study was to examine the possible effects of 12 months of treatment with different serotonergic drugs, such as clomipramine and selective serotonin reuptake inhibitors (SSRIs) on peripheral immunological cells of 18 OCD patients. Both the absolute number and percent of CD4+, CD8+, CD3+, CD19+ and CD56+ cells were measured in peripheral blood before and after treatment by means of a Facstar Flow Sorter apparatus. At baseline, all patients showed a significant increase of CD8+ and decrease of CD4+ lymphocytes when compared with a similar group of healthy control subjects; after the treatment, CD8+ and CD4+ cells, respectively, decreased and increased significantly, and the CD4+/CD8+ ratio increased, when compared with baseline values, in parallel with the clinical improvement. These data suggest that the alterations of immune cells reported in patients with OCD at baseline may be reverted by treatment with SRIs and should be considered a state-dependent marker, perhaps related to a condition of stress.

Adenylate-cyclase activity in platelets of patients with obsessive-compulsive disorder

Although the main biological hypothesis on the pathophysiology of obsessive-compulsive disorder (OCD) is centered on the serotonin system, indications are available that other neurotransmitters, and even second messengers, particularly the cyclic adenosine monophosphate (cAMP) signaling, may be involved, though effective data are few. Therefore, the aim of the present study was to evaluate and compare the basal and isoprenaline (ISO)-stimulated velocity of adenylate-cyclase (AC) in human platelet membranes of patients with OCD and healthy control subjects. The results showed that the basal and ISO-stimulated AC activity, as well as the dose-response curves of ISO by using agonist concentrations ranging between 0.1 nM and 10 muM, were not different in the two groups. However, OCD patients showed lower EC(50) and higher E(max) values than healthy subjects. These findings suggest the presence of supersensitive beta-adrenergic receptors in platelets of OCD patients.

Synthesis and biological affinity of new imidazo- and indol-arylpiperazine derivatives: further validation of a pharmacophore model for alpha(1)-adrenoceptor antagonists

In the continuing search for selective alpha(1)-adrenoceptor (AR) antagonists, new alkoxyarylpiperazinylalkylpyridazinone derivatives were designed and synthesized. The new compounds were tested for their affinity toward alpha(1)-AR, alpha(2)-AR and 5-HT(1A) receptors. The ability of these compounds to inhibit the serotonin transporters (SERT) was also determined. The pharmacological data confirm that increasing the size of the ortho alkoxy substituent on the phenyl ring of the arylpiperazine moiety afforded compounds with enhanced affinity toward the alpha(1)-AR. The isopropoxy group, the largest group evaluated, led the best alpha(1)-AR affinity profile. In contrast, the compounds which have an amide group within of the o-alkoxy-phenylpiperazine fragment showed low affinity toward the receptors studied. Similar results were obtained when the amide group was present in the linker of the junction between the two major constituents of the molecule.

Thermal balneotherapy induces changes of the platelet serotonin transporter in healthy subjects

Although the beneficial effects of balneotherapy have been recognized since a long time, a few information is available on the biological mechanisms underlying them and the subjective feelings of increased well-being and mood. The links between the serotonin (5-HT) system and mood prompted us to investigate the 5-HT platelet transporter (SERT), which is considered a reliable, peripheral marker of the same structure present in presynaptic neurons, in 20 healthy volunteers before (t0) and 30 min after (t1) thermal balneotherapy with ozonized water of Montecatini spa, as compared with a similar group who underwent a bath in non-mineral water. The SERT was evaluated by means of the specific binding of (3)H-paroxetine ((3)H-Par) to platelet membranes. Equilibrium-saturation binding data, the maximal binding capacity (Bmax) and the dissociation constant (Kd), were obtained by means of the Scatchard analysis. The results showed that, while Bmax values did not change in both groups, the Kd values decreased significantly at t1 only in those subjects who bathed in ozonized water. The results of this study, while showing a decrease of the dissociation constant (Kd) which is the inverse of affinity constant, of (3)H-Par binding to SERT in all subjects after balneotherapy and not in those bathing in normal water, suggest that SERT modifications may be related to a specific effect of ozonized water and, perhaps, also to the increased sense of well-being.

Reduced midbrain-pons serotonin transporter binding in patients with obsessive-compulsive disorder

OBJECTIVE

To evaluate current hypothesis regarding the pathophysiology of obsessive-compulsive disorder (OCD) by studying the serotonin receptor binding in patients with OCD using single photon emission computerized tomography (SPECT).

METHOD

We studied nine patients (four men and five women, age range 21-56 years) fulfilling the DMS-III-R criteria for OCD using SPECT and the serotonin transporter (SERT) tracer (123)I-beta-CIT. SERT binding potential (BP2) was determined by Logan plot derived from seven scans obtained during 10-400 min.

RESULTS

The binding of (123)I-beta-CIT in midbrain-pons was reduced in OCD patients when compared with controls (BP2 0.97 +/- 0.07 vs. 0.84 +/- 0.12, P = 0.011). There was no correlation between BP2 and any of the clinical variables (age at onset, disease duration, and Yale-Brown Obsessive-Compulsive Scale score).

CONCLUSION

This study suggests a reduced serotonergic input into the fronto-subcortical circuits in OCD, thereby diminishing the inhibitory regulation of serotonin on these circuits.

Meta-analysis of the association of serotonin transporter gene polymorphism with obsessive-compulsive disorder

Evidence has supported a role for serotonin system dysfunction in the pathogenesis of the obsessive-compulsive disorder (OCD). Many studies examined the association between OCD and a functional polymorphism of the serotonin transporter gene promoter (5-HTTLPR) but yielded inconsistent results. Current study aimed to determine conclusively whether there is an association by using a meta-analytic method. Over 3000 subjects from 13 independent case-control association studies were included in the analysis. By using random effects model, data from these studies were pooled to compare the genotypes and allelic distribution of the 5-HTTLPR polymorphism between OCD patients and control subjects. In the analysis, OCD was found to be associated with the SS homozygous genotype (OR=1.21, p=0.04), but was inversely associated with the LS heterozygous genotype (OR=0.79, p=0.03). No association with the LL homozygous genotype or the allelic distribution was found. These results suggest that variations of the serotonin transporter gene influence the risk of OCD, but their functional roles in the pathogenesis of OCD need to be elucidated.

Alteration of serotonin transporter density and activity in fibromyalgia

The aim of the study was to evaluate the kinetic parameters of a specific serotonin transporter (SERT) and serotonin uptake in a mentally healthy subset of patients with fibromyalgia. Platelets were obtained from 40 patients and 38 healthy controls. SERT expression and functionality were evaluated through the measurement of [³H]paroxetine binding and the [³H]serotonin uptake itself. The values of maximal membrane binding capacity (B_max) were statistically lower in the patients than in the healthy volunteers, whereas the dissociation constant (K_d) did not show any statistically significant variations. Moreover, a decrease in the maximal uptake rate of SERT (V_max) was demonstrated in the platelets of patients, whereas the Michaelis constant (K_m) did not show any statistically significant variations. Symptom severity score (tiredness, tender points index and Fibromyalgia Impact Questionnaire) were negatively correlated with B_max and with V_max, and positively correlated with K_m. A change in SERT seems to occur in fibromyalgic patients, and it seems to be related to the severity of fibromyalgic symptoms.

The genetic studies of obsessive-compulsive disorder and its future directions

Obsessive-compulsive disorder (OCD) is characterized by recurrent and persistent thoughts (obsessions), and repetitive behaviors or mental acts (compulsions). In Korea, an epidemiological study reported that the lifetime prevalence of OCD in the population was greater than two percent. The exact cause of OCD is still unknown. Evidence from familial, twin and segregation studies supports the role of a genetic component in the etiology of OCD. In addition, there is growing evidence that OCD has a specific neurochemical and neuroanatomical basis. According to this evidence, researchers have selected various candidate genes which have been implicated in the neurophysiology of OCD, and differences of allelic variants in OCD patients and controls have been analyzed. In this review we will introduce the results of previous genetic studies of OCD which have been performed in other populations, including twin studies, family studies, segregation analyses, linkage analyses, and association studies. In addition to these studies, we will present the results of our genetic studies of OCD performed in Korea.

Low density and high affinity of platelet [3H]paroxetine binding in women with bulimia nervosa

Impaired serotonin transmission has been suggested to be implicated in the pathophysiology of bulimia nervosa. As an indirect measure of brain serotonergic activity, the binding of tritiated ligands to platelet serotonin transporters has been studied in bulimia nervosa as well as in other putatively serotonin-related psychiatric disorders. In this study, the density and affinity of platelet serotonin transporters were assessed in 20 women meeting the DSM-IV criteria for bulimia nervosa and in 14 controls without previous or ongoing eating disorder using [(3)H]paroxetine as a ligand. In comparison to controls, women with bulimia nervosa had a significantly reduced number of platelet binding sites (B(max) = 721 +/- 313 vs. 1145 +/- 293 fmol/mg protein) and an increase in the affinity for the ligand demonstrated by a lower dissociaton constant (K(d) = 33 +/- 10 vs. 44 +/- 10 pM). A significant correlation between B(max) and K(d) values was found in patients but not in controls. Our results support the notion that bulimia nervosa is associated with a reduction in platelet serotonin transporter density. In addition, our study is the first to report that this reduced transporter density in women with bulimia nervosa is accompanied by an increase in the affinity of the transporter for the ligand.

Obsessive-compulsive disorder, factor-analyzed symptom dimensions and serotonin transporter polymorphism

Recently, on the basis of the effects of serotonin (5-HT) reuptake inhibitors in obsessive-compulsive disorder (OCD) treatment, several candidate genes related to 5-HT regulation have been hypothesized to play an important role in the development of OCD. One of them is 5-HT transporter gene. Therefore, the aims of this study were to investigate the associations between 5-HT transporter polymorphism and OCD. One hundred and twenty-four OCD patients and 171 normal controls participated in this study. Genomic DNA was extracted from their blood. Comparison of the genotypes and allele frequencies of the SERTPR polymorphism between the OCD group and the control group was made. Using principal component analysis, we derived four factors from thirteen main contents of the Y-BOCS checklist and investigated the association between these four factors and the SERTPR polymorphism. In this case-control study, we could not find any associations between the SERTPR polymorphism and the development of OCD. In the OCD group, patients with the L genotype had higher scores for the religious/somatic factor than with the S genotype. In conclusion, the SERTPR polymorphism does not affect the development of OCD. But SERTPR polymorphisms affect certain factors of OC symptoms. Moreover, the factor analytic approach used in the present study has identified meaningful symptom dimensions to help guide future research.

Animal models with potential applications for screening compounds for the treatment of obsessive-compulsive disorder

The availability of an animal model for obsessive-compulsive disorder (OCD) is necessary for the development of novel pharmacological treatments. To be useful, the model must be predictive of clinical performance, possess characteristic criteria and distinguish anti-OCD from antidepressant compounds. Due to the lack of OCD models useful for drug discovery, all compounds currently used for OCD were developed first as antidepressants. In this article, we discuss the relative merits of: stereotypic behaviours (canine acral lick, feather picking, amphetamine- and 5-HT-induced stereotypy); adjunctive and displacement behaviours (schedule-induced polydipsia, wheel running, resident-intruder grooming); anxiolytic tests (separation and shock-induced ultrasonic vocalisation and marble burying); and depression tests (inescapable shock-induced escape and immobility in forced swim) as potential OCD models. We conclude that adjunctive and displacement behaviours, and in particular schedule-induced polydipsia, may prove to be the best models for compulsive behaviour in animals that can be used for the discovery of novel anti-OCD agents.

Influence of menstrual cycle on platelet serotonin uptake site and serotonin2A receptor binding

Depression and anxiety are common health problems affecting women, particularly during the reproductive years. Major depression is two to three times as common in women than in men. Neuroendocrine factors are likely to contribute to this overall increased risk for developing mood disorders in women, and the neuroendocrine influence is most obviously seen in women with premenstrual dysphoric disorder (PMDD) as these women experience depressed mood and anxiety premenstrually only during ovulatory cycles. Moreover, dysfunction of serotonergic transmission has been regarded as an important mechanism in several psychiatric disorders and ovarian steroids have been shown to profoundly influence the activity of the serotonergic system. Given these facts, the purpose of this study was to examine whether binding of [3H]paroxetine to the platelet serotonin transporter or binding of [3H]lysergic acid diethylamide ([3H]LSD) to the platelet 5-HT2A receptor are influenced by the cyclical changes in circulating estradiol and progesterone that occur during the menstrual cycle. We examined 28 healthy women, without oral contraceptives and with regular menstrual cycles. In the late follicular phase, Bmax for [3H]paroxetine binding was significantly higher than in the ovulatory (p<0.01), early luteal phase (p<0.05) and mid-luteal phase (p<0.01). Bmax for [3H]LSD binding was significantly higher in the early follicular phase and the early luteal phase compared to the mid-luteal phase (p<0.001 and p<0.05, respectively). In the early follicular phase and the ovulatory phase, significant correlations between estradiol serum concentrations and Kd for [3H]paroxetine were obtained (p<0.001, respectively). In the luteal phase, significant inverse correlations between progesterone as well as estradiol serum concentrations and Kd for [3H]LSD binding were found (p<0.05, respectively).

Platelet serotonergic predictors of clinical improvement in obsessive compulsive disorder

OBJECTIVE

Serotonin reuptake inhibitors (SRIs) are the most efficient pharmacological treatment of obsessive-compulsive disorders (OCD). Previous studies have suggested that some peripheral serotonergic parameters can be used to predict the clinical outcome of the treatment of OCD patients with SRIs. We tried to identify further peripheral serotonergic parameters that could help predict the clinical outcome of SRI treatment in a sample of patients with OCD.

METHODS

We compared 19 OCD patients before and after 8 weeks of SRI treatment with 19 sex-matched and age-matched controls. We assessed clinical improvement and whole-blood serotonin (5-HT) concentration, platelet 5-HT transporter (5-HTT) and 5-HT2A receptor binding characteristics and platelet IP3 content.

RESULTS

Before treatment, OCD patients had higher platelet IP3 content and fewer 5-HTT binding sites than the controls. Treatment with SRIs further lowered the number of 5-HTT binding sites, normalized platelet IP3 contents, and lowered the number of platelet 5-HT2A binding sites and whole-blood 5-HT concentrations below control values. The patients who improved most following SRI treatment had higher whole-blood 5-HT concentrations before treatment.

CONCLUSION

Our results confirm that whole-blood 5-HT concentration is a predictor for clinical improvement and indicate that abnormal intracellular mechanisms may be involved in OCD patients, in particular, the overstimulation of the phosphoinositide signaling system.

Platelet serotonin transporter in patients with diarrhea-predominant irritable bowel syndrome both before and after treatment with alosetron

OBJECTIVES

Serotonin reuptake is mediated by a transporter protein (SERT), and its dysfunctions can alter serotonergic transmission. The present study examines the binding profile of platelet SERT in healthy volunteers as well as in patients with diarrhea-predominant irritable bowel syndrome (D-IBS), both before and after treatment with the 5-HT(3) receptor antagonist alosetron.

METHODS

Binding of [(3)H]paroxetine to SERT was assayed in platelet membranes collected from D-IBS patients (12 women, age 21-73 yr) and healthy volunteers (12 women, age 24-68 yr). Both maximal binding capacity (B(max)) and dissociation constant (K(d)) were estimated. In D-IBS patients, binding parameters and symptom severity score were evaluated at baseline and after treatment with alosetron (1 mg b.i.d. for 8 wk).

RESULTS

At baseline, B(max) and K(d) values of [(3)H]paroxetine binding were respectively lower and higher in D-IBS patients than in healthy volunteers (B(max): 518.7 +/- 155.9 vs 1151.9 +/- 187.4 fmol/mg, p < 0.001; K(d): 0.19 +/- 0.05 vs 0.06 +/- 0.02 nmol/L, p < 0.001). Symptom severity score in D-IBS patients (50.9 +/- 18.8) was negatively correlated with B(max) (r = -0.964; p < 0.001) but not K(d) values (r = -0.164; p = 0.609). After treatment with alosetron, symptom severity score decreased significantly (14.4 +/- 3.7; p < 0.001), whereas B(max) (522.7 +/- 39.7 fmol/mg) and K(d) values (0.17 +/- 0.07 nmol/L) did not change.

CONCLUSIONS

The present results indicate that SERT expressed on platelet membranes of D-IBS patients is characterized by low density and binding affinity and suggest a possible correlation between the reduced capacity of serotonin reuptake and the severity of D-IBS symptoms.

Serotonin transporter gene polymorphisms and platelet [3H] paroxetine binding in premenstrual dysphoria

The purpose of this study was to investigate if women with premenstrual dysphoria differ from controls with respect to the number of platelet serotonin transporters, and with respect to three polymorphisms in the gene coding for the serotonin transporter: a 44 base pair insertion/deletion in the promoter region, a variable number of tandem repeats in the second intron, and a single nucleotide polymorphism in the 3' untranslated region. Also, the possible relationship between the three polymorphisms and platelet serotonin transporter density was analyzed. The density of platelet [(3)H]paroxetine binding sites was significantly lower in women with premenstrual dysphoria than in controls, but patients and controls did not differ with respect to allele or genotype frequency for any of the three polymorphisms examined. A significant association between the number of platelet serotonin transporters and the promoter polymorphism was observed, subjects being homozygous for the short (deletion) variant having higher platelet serotonin transporter density than subjects carrying the long (insertion) allele. The results support the assumption that serotonin-related psychiatric disorders-such as premenstrual dysphoria-may be associated with a reduction in platelet [(3)H]paroxetine binding, but argue against the notion that this reduction is due to certain variants of the serotonin transporter gene being more common in patients than in controls.

Decreased inhibitory activity of PKC in OCD patients after six months of treatment

We investigated 5-HT reuptake and protein kinase of type C (PKC) activation in platelets of 14 OCD patients at baseline and after six months of treatment with different serotonin (5-HT) reuptake inhibitors (SRIs). The results showed that all SRIs provoked a significant increase in both the maximal velocity (V(max)) and the Michaelis-Menten constant (K(m)) of 5-HT reuptake, as compared with baseline values. The activation of PKC by means of 4-beta-12-tetradecanoylphorbol 13-acetate provoked a significant decrease in V(max) values, but the effect was not as evident as at baseline. These findings could indicate that, in OCD patients, SRIs increase the rate of reuptake and decrease the inhibitory effect of PKC and that the two phenomena may be linked, the first perhaps depending upon the second.

Decreased platelet [3H]paroxetine binding sites in suicide attempters

Research to date would suggest the possible involvement of the serotonin (5-HT) system in the pathophysiology of suicide. With this study, we aimed to investigate the platelet 5-HT transporter, by means of the specific binding of tritiated paroxetine ([3H]Par), in a sample of 20 suicide attempters recruited at a first-aid service, as compared with healthy control subjects and psychiatric patients with no current or previous history of suicide attempt. The results, showing a decreased number of [3H]Par binding sites in suicide attempters, would suggest the involvement of the presynaptic 5-HT transporter in self-aggressive behavior.

Regional cerebral blood flow abnormalities in early-onset obsessive-compulsive disorder: an exploratory SPECT study

OBJECTIVE

Recent epidemiological and clinical data suggest that obsessive-compulsive disorder (OCD) may be subtyped according the age of onset of obsessive-compulsive symptoms. The regional cerebral blood flow (rCBF) single photon emission computed tomography (SPECT) technique was used to investigate whether the pathophysiology of OCD differs between early- and late-onset OCD subjects.

METHOD

Resting rCBF was measured in 13 early-onset (<10 years) and 13 late-onset (>12 years) adult OCD subjects and in 22 healthy controls. Voxel-based rCBF comparisons were performed with statistical parametric mapping.

RESULTS

Early-onset OCD cases showed decreased rCBF in the right thalamus, left anterior cingulate cortex, and bilateral inferior prefrontal cortex relative to late-onset subjects (p < .0005, uncorrected for multiple comparisons). Relative to controls, early-onset cases had decreased left anterior cingulate and right orbitofrontal rCBF, and increased rCBF in the right cerebellum, whereas late-onset subjects showed reduced right orbitofrontal rCBF and increased rCBF in the left precuneus. In early-onset subjects only, severity of obsessive-compulsive symptoms correlated positively with left orbitofrontal rCBF.

CONCLUSIONS

rCBF differences in frontal-subcortical circuits between early-onset and late-onset OCD subjects were found, both in location and direction of changes. These results provide preliminary evidence that brain mechanisms in OCD may differ depending on the age at which symptoms are first expressed.

Is obsessive-compulsive disorder caused by a second-messenger imbalance?

Although the precise etiologic nature of obsessive-compulsive disorder (OCD), one of the most common psychiatric conditions, is unknown, several findings indicate involvement of the serotonin (5-HT) transporter. Apart from the specific effects of selective 5-HT reuptake inhibitors, other studies show decreased functionality of the platelet 5-HT transporter in OCD. In this report, the authors combine data from two independent studies of patients with OCD, showing both an increased activity of protein kinase type C (PKC) and a decreased activity of protein kinase type A (PKA). The authors propose a unifying hypothesis that OCD might be determined by an imbalance between PKC and PKA, with a prevalence of the former and, more generally, of the phosphoinositide over the cyclic adenosine monophosophate (cAMP) pathway. Should this hypothesis prove correct, the path would be open for new therapeutic interventions in the treatment of OCD.

Decreased platelet 3H-paroxetine binding in untreated panic disorder patients

Different findings support the involvement of the serotonin (5-HT) system in panic disorder. The presence of the 5-HT transporter in blood platelets similar to that in presynaptic serotonergic neurons, permits the investigation of this structure in periphery. We therefore evaluated the binding of 3H-paroxetine, a selective 5-HT reuptake inhibitor which is considered the ligand of choice for labelling the 5-HT transporter, in platelets of 20 drug-free patients with panic disorder. The same measurement was repeated after one year's treatment with different drugs. The results showed patients to have a lower number of 3H-paroxetine sites than a group of age- and sex-matched controls, thus suggesting the involvement of the 5-HT transporter in panic disorder. This abnormality reverted after one year of treatment with specific drugs that provoked the symptom remission in all cases, which would suggest a link with the clinical improvement.

Self-help and guided self-help treatments for bulimia nervosa and binge eating disorder

This article reviews the use of self-help and guided self-help treatments for bulimia nervosa (BN) and binge eating disorder (BED). Available data suggest that self-help and guided self-help treatments based on empirically-supported cognitive behavioral therapies (CBT) have efficacy for binge eating problems. Emerging findings from initial studies suggest that the magnitude of the differences in outcomes between certain guided-self-help CBT programs and therapist-led CBT may not be substantial, although further research is clearly indicated. Initial data suggest that self-help and guided self-help CBT programs may not only demonstrate "efficacy" but also "effectiveness"-i.e., utility in "real-world" primary care or community settings. Implications for clinical practice and for future research are discussed.

Platelet [3H]paroxetine binding in patients with OCD-related disorders

The recently introduced notion of clinical conditions being related one to another, the spectrum concept, permits the testing of the involvement of serotonergic systems in a broad range of disorders tentatively linked to obsessive-compulsive disorder (OCD) for which no pathophysiological hypotheses yet exist. We therefore compared the binding of [3H]paroxetine ([3H]Par), a ligand that specifically labels the serotonin (5-HT) transporter, in platelets of drug-free outpatients suffering from various OCD-related disorders with binding in platelets of OCD patients and healthy subjects. Diagnoses were made according to DSM-IV criteria. The most frequent diagnosis was that of body dysmorphic disorder, followed by impulse control disorder, kleptomania, Tourette's syndrome and trichotillomania. Platelet membranes and [3H]Par binding were studied according to standardized protocols. The results, showing a similarly decreased density of [3H]Par binding sites in both patient groups as compared with healthy subjects, suggest the presence of a shared abnormality at the level of the presynaptic 5-HT transporter, probably linked to a common dimension yet to be identified.

Immunological alterations in adult obsessive-compulsive disorder

BACKGROUND

Some recent findings suggest the involvement of autoimmune mechanisms in childhood onset of obsessive-compulsive disorder (OCD), on the basis of a parallel drawn with Sydenham's chorea, a manifestation of rheumatic fever. A monoclonal antibody called D8/D17 characterizing a B-lymphocyte antigen, present in almost all patients with rheumatic fever, has been found also in children affected by OCD, Tourette syndrome, and chronic tics to a greater degree than in healthy control subjects. The few observations of disturbances of some immunologic parameters in adult OCD patients, prompted the authors to investigate and compare subsets of peripheral immunological cells for differences in adult patients with OCD and healthy control subjects.

METHODS

Twenty patients suffering from OCD, with no comorbidity for other psychiatric disorders, were compared with a similar group of healthy control subjects. The immune subsets were measured by flow cytometry.

RESULTS

The CD8+ lymphocytes were significantly increased and CD4+ lymphocytes significantly decreased in OCD patients, while the other cells did not differ between the two groups. No correlation was found between immunologic and clinical parameters.

CONCLUSIONS

These data indicate that patients with adult OCD showed increased CD8+, i.e., suppressor T lymphocytes, and decreased CD4+, which identify helper T lymphocytes, as compared with a similar group of healthy control subjects. The findings appear peculiar to patients with OCD and are suggestive of an immunologic imbalance, which might be related to the stress deriving from the frustrating situation determined by the disorder itself.

Regulation of the platelet serotonin transporter by protein kinase C in the young and elderly

BACKGROUND

Some data show that different factors may influence the serotonin (5-HT) uptake rate. Our study aimed at evaluating the possible role of a protein kinase C (PKC) activator, i.e., 4-beta-12-tetradecanoylphorbol-13-acetate (beta-TPA) on the platelet 5-HT uptake of young and elderly subjects, through the measurement of the 5-HT uptake itself and 3H-paroxetine ([3H]PAR) binding sites, which correspond to the transporter protein.

METHODS

Human platelets and 5-HT uptake were evaluated according to the method of Arora and Meltzer, while [3H]PAR binding was performed following the Marazziti et al method.

RESULTS

The results showed that beta-TPA reduced significantly the maximal velocity (Vmax) of 5-HT uptake, with no change in the Michaelis constant or in [3H]PAR binding parameters, in platelets of both young and elderly subjects. Although this last group of subjects had a significantly lower Vmax than the other, the degree of inhibition was almost the same (75%) in both.

CONCLUSIONS

These findings indicate that PKC decreases the 5-HT uptake rate by modifying the phosphorylation state of the transporter and with no change in the number of [3H]PAR binding sites. The responsiveness of this pathway is identical in both young and elderly subjects.

Effect of aging and sex on the [3H]-paroxetine binding to human platelets

Since there exist conflicting results with regard to the possible effect of aging on platelet [3H]-imipramine binding, taken as a peripheral marker of the serotonin (5-HT) transporter, we reinvestigated this matter by comparing the binding of the more selective ligand [3H]-paroxetine in 20 aged and 23 young subjects. The results showed that neither the maximum binding capacity nor the dissociation constant (Kd) were significantly different in the two groups. When the subjects were compared according to sex, the young females revealed a statistically significant lower Kd than the males, while the contrary was true for the aged females. The Kd was significantly and negatively correlated to age in males. In addition, a significant age x gender interaction was also observed. Therefore, the sex of a subject would seem to provoke significant age-related changes in the Kd of [3H]-paroxetine binding to platelet membranes. This might indicate modifications in the 5-HT transporter that could form the basis of a sex-related difference in vulnerability to disorders, such as depression, where a dysfunction at this level is hypothesized.