Serotonergic responsivity in obsessive-compulsive disorder. Effects of chronic clomipramine treatment

Clomipramine is a potent serotonin reuptake blocker that decreases the symptoms of obsessive-compulsive disorder (OCD). To investigate whether clomipramine treatment in OCD affects brain serotonergic responsiveness, metachlorophenylpiperazine (mCPP), a selective serotonin agonist, and placebo were given under double-blind conditions to nine patients with OCD before and after treatment with clomipramine. Unlike our previous observations of a marked transient increase in obsessional symptoms and anxiety following 0.5 mg/kg of mCPP, readministration of mCPP after four months of treatment with clomipramine did not significantly increase obsessional symptoms and anxiety. Similarly, the hyperthermic effect of mCPP observed before treatment was eliminated after treatment with clomipramine. These findings are consistent with the development of adaptive subsensitivity to the serotonergic agonist mCPP during clomipramine treatment. A similar alteration in the response to endogenous serotonin may mediate clomipramine's antiobsessional effects.     

Metergoline blocks the behavioral and neuroendocrine effects of orally administered m-chlorophenylpiperazine in patients with obsessive-compulsive disorder

The pharmacological probe, meta-chlorophenylpiperazine (m-CPP), administered orally to patients with obsessive-compulsive disorder (OCD) has been shown to induce an acute exacerbation in OCD symptoms as well as an exaggerated anxiogenic response in comparison with controls. The mechanism of m-CPP's behavioral effects in humans remains controversial. To further study m-CPP's actions in OCD patients, we completed a series of double-blind pharmacological challenges in 12 OCD patients. Six OCD patients received four separate challenges: placebo, metergoline, m-CPP, and metergoline plus m-CPP; the second group (n = 6) received metergoline and metergoline plus m-CPP in separate challenges. OCD patients receiving placebo or metergoline alone failed to show evidence of significant changes on any of the behavioral rating scales, in contrast to the patients who received m-CPP alone who exhibited significant increases in anxiety and OCD symptoms. However, the 12 OCD patients who received pretreatment with metergoline before m-CPP experienced no significant changes from baseline OCD symptoms or other behavioral changes. m-CPP's ability to elicit elevations in plasma prolactin was blocked by metergoline pretreatment. Metergoline's ability to block m-CPP's effects on behavior and plasma prolactin lends further support to a serotonergic mediation of m-CPP's effects, including its elicitation of OCD symptoms.     

Obsessive-compulsive disorder: psychobiological approaches to diagnosis, treatment, and pathophysiology

The diagnosis, treatment, and pathophysiology of obsessive-compulsive disorder (OCD) were examined in a series of studies utilizing psychobiological approaches. Putative biological markers previously reported in depression were studied in this disorder and revealed that on some measures [Dexamethasone Suppression Test and rapid eye movement (REM) latency on sleep electroencephalogram (EEG)], OCD patients resemble those with major depressive disorder (MDD), whereas on others [REM density, platelet serotonin uptake, probably platelet 3H-imipramine binding, and 5-hydroxy-indoleacetic acid (5-HIAA) in cerebral spinal fluid (CSF)] they do not. The relationship between OCD and MDD was further explored in a double-blind, randomized crossover study designed to compare the antiobsessional effects of two tricyclic antidepressants, clomipramine (CMI) and desipramine (DMI), in a nondepressed cohort of OCD patients. CMI was found to have significant antiobsessional effects in this group, whereas in the same patients, DMI lacked therapeutic effects. These results suggest that not all antidepressants are antiobsessive and that some property of CMI, such as its potent serotonergic effects, may be of pathophysiological relevance for OCD. The role of serotonin in this disorder was then tested using the pharmacological challenge strategy. A novel serotonin postsynaptic receptor (5HT-1) agonist, m-chlorophenylpiperazine (m-CPP), was administered orally (0.5 mg/kg) under double-blind, placebo-controlled conditions to OCD patients and controls. In addition, a serotonergic receptor antagonist, metergoline (4 mg), was given to a subset of OCD patients. Relative to healthy volunteers, the OCD patients became significantly more anxious, depressed, and dysphoric after m-CPP administration. Moreover, in the OCD patients, obsessive-compulsive symptoms increased markedly after m-CPP and decreased significantly following metergoline administration. These results demonstrate that agents that bind to the 5HT-1 receptor can acutely affect the symptoms of OCD patients. The striking behavioral effects of these direct postsynaptic receptor ligands and the relative specificity of clomipramine as an antiobsessional agent suggest that serotonergic neurons may play a role in the pathophysiology, as well as mediating the pharmacological reduction, of obsessional symptoms.     

Effect of acute intravenous clomipramine and antiobsessional response to proserotonergic drugs: is gender a predictive variable?

BACKGROUND: Previous studies on serotonergic responsivity in obsessive-compulsive disorder (OCD) showed about 50% of patients experiencing an acute worsening of OC symptoms when administered meta-chlorophenylpiperazine or i.v. clomipramine. The aim of this study was to determine what variables influence the response to acute i.v. clomipramine. Could this response be predictive of the response to chronic treatment with two serotonergic drugs with differing selectivity profiles: clomipramine and fluvoxamine? METHODS: Fifty OC patients were consecutively recruited. All underwent a challenge with 25 mg i.v. clomipramine and placebo and were administered 10-week oral clomipramine or fluvoxamine according to a double-blind design. The efficacy of the antiobsessional treatment was evaluated by Yale-Brown Obsessive-Compulsive Scale and Clinical Global Impression scale scores. RESULTS: Obsessions worsened in 42% patients as rated by change values in 100-mm visual analogue scale scores for the clomipramine vs. placebo infusion. There was a significant difference in gender distribution between "worsened" and "unchanged" patients, since female subjects were more frequently "unchanged." Thirty-one patients completed the 10-week treatment. According to both qualitative and quantitative evaluations, female subjects showed a better antiobsessional response, and this difference was enhanced in the clomipramine-treated group. CONCLUSIONS: Results suggest a role for reproductive hormones in the pathophysiology or treatment of OC patients.     

Acute intravenous administration of ondansetron and m-CPP,alone and in combination,in patients with obsessive–compulsive disorder (OCD): behavioral and biological results

Obsessive–compulsive disorder (OCD) has been linked to abnormal function of brain serotonin (5-HT) pathways. Since ondansetron is a highly selective 5-HT₃ receptor antagonist, the present study was undertaken to investigate 5-HT₃ function in OCD. We administered m-CPP (0.08 mg/kg i.v.) and the potent 5-HT₃ antagonist, ondansetron (0.15 mg/kg i.v.), to 11 OCD patients. All of the subjects received four separate challenges (m-CPP+placebo, m-CPP+ondansetron, ondansetron+placebo and placebo+placebo). In comparison to placebo, administration of m-CPP was associated with significant behavioral effects, particularly self-rated measures of anxiety, altered self-reality, functional deficit and OCD symptoms. Pretreatment with ondansetron did not affect any of the self-rated behavioral symptoms. After administration of m-CPP relative to placebo, significant increases in plasma cortisol and prolactin were found. These changes were not affected by ondansetron. In conclusion, our results do not support the hypotheses that 5-HT₃ receptor-mediated mechanisms modulate m-CPP's behavioral and neuroendocrine effects in patients with OCD.     

Prolactin and cortisol responses to MK-212, a serotonin agonist, in obsessive-compulsive disorder

To examine further the serotoninergic system in obsessive-compulsive disorder (OCD), the plasma concentrations of cortisol and prolactin and the behavioral responses after oral administration of MK-212 (6-chloro-2-[1-piperazinyl]-pyrazine), a serotonin agonist, and placebo were studied in 17 patients with OCD and nine normal controls. The two groups did not differ significantly in basal plasma prolactin or cortisol levels. Nevertheless, both the prolactin and cortisol response to oral administration of MK-212 (20 mg) were significantly blunted in the patients with OCD compared with those of the normal controls. MK-212 did not affect the intensity of OCD symptoms. However, MK-212, as compared with placebo, produced slight but statistically significant increases in self-ratings of nausea, dizziness, anxiety, feeling strange, and mixed feelings of calmness and restlessness, as well as depression and feeling high. These behavioral ratings were not significantly different in patients and normal controls. These findings are consistent with previous reports of diminished serotoninergic responsivity in OCD and raise the possibility of subsensitivity of at least some serotonin receptors in this disorder.     

Effects of chronic fluoxetine treatment on behavioral and neuroendocrine responses to meta-chlorophenylpiperazine in obsessive-compulsive disorder

To investigate the effect of fluoxetine on serotonergic sensitivity in obsessive-compulsive disorder (OCD), the partial serotonin agonist metachlorophenylpiperazine (mCPP) was compared to placebo under double-blind conditions in six patients with OCD before and during treatment with fluoxetine. Readministration of oral mCPP (0.5 mg/kg) after at least 12 weeks of fluoxetine treatment did not increase obsessive-compulsive (OC) symptoms, in contrast to exacerbation of OC symptoms produced by mCPP before treatment. Chronic fluoxetine treatment resulted in a significant increase in prolactin and cortisol response to mCPP. This may be accounted for, however, by substantially increased plasma mCPP levels during fluoxetine treatment. Chronic fluoxetine treatment diminished the behavioral sensitivity to mCPP and did not diminish, but may have partially normalized, the neuroendocrine response to mCPP in patients with OCD. These adaptive homeostatic effects may reflect fluoxetine's antiobsessional mechanism.     

Effects of catecholamine depletion with AMPT (alpha-methyl-para-tyrosine) in obsessive-compulsive disorder.

BACKGROUND: Several lines of evidence suggest that brain dopamine function may contribute to some obsessive-compulsive (OC) phenomena. The effects of catecholamine depletion were examined in drug-free patients with obsessive-compulsive disorder (OCD). METHODS: The tyrosine hydroxylase inhibitor alpha-methyl-para-tyrosine (AMPT) and diphenhydramine hydrochloride (placebo) were administered for three consecutive days, one week apart, to 6 drug-free adult OCD patients without a personal or family history of chronic tics, in a double-blind, randomized design. The effects of AMPT and placebo on OC, depression, anxiety and global clinical symptoms were assessed. RESULTS: AMPT produced no clinically or statistically significant change in any behavioral ratings, including OC symptom severity, compared with placebo. CONCLUSIONS: Acute reduction of catecholamine levels does not seem to affect OC symptoms in drug-free patients with OCD. Studies of catecholamine depletion with AMPT in patients with comorbid OCD and chronic tics may be of considerable neurobiological and clinical interest.     

Trazodone treatment in clomipramine-resistant obsessive-compulsive disorder

Trazodone (TZ) was administered to nine patients suffering from obsessive-compulsive disorder (OCD), who failed to respond to either clomipramine (CMI) or to CMI plus lithium carbonate. The group, as a whole, showed significant but mild improvement. Three patients responded very favorably to TZ. In these three responders, efficacy was substantiated by the return of the original obsessive-compulsive (OC) symptoms following TZ withdrawal and their amelioration after its readministration. Interestingly, the aggravation of OCD symptomatology that has been associated with a specific TZ metabolite was not observed. This study is consistent with previous reports of the anti-OC efficacy of TZ and suggests the involvement of complex serotonergic mechanisms in the pathophysiology of this disorder.     

Serotonin and dopamine antagonism in obsessive-compulsive disorder: effect of atypical antipsychotic drugs

BACKGROUND: Previous reports suggest that some atypical antipsychotics may have obsessogenic as well as antiobsessional effects. Given their higher affinity for serotonin 5HT2 receptors than dopamine D2 receptors, it has been speculated that atypical antipsychotics may induce obsessive-compulsive (OC) symptoms, even at low doses, due to high 5HT2 antagonism, whereas improvement in OC symptoms is thought to occur only at high doses due to high D2 antagonism. METHOD: In this open case series, the dose-response relationship of atypical antipsychotic augmentation in the treatment of obsessive compulsive disorder (OCD), and the dose-severity relationship in atypical anti psychotic-induced OC symptoms were examined. Three patients were identified who had either refractory OCD or OC symptoms following administration of atypical antipsychotics such as olanzapine and risperidone. RESULTS: Case 1: A linear dose-response relationship between increasing doses of olanzapine and improvement in OC symptoms was observed in an OCD patient resistant to 5-HT reuptake inhibitors. 2: OC symptoms induced by low doses of risperidone (1 mg) were reversed by increasing the doses of risperidone (3 mg) in a bipolar disorder patient suggesting an inverse dose-severity relationship. 3: No inverse dose-severity relationship was noted between olanzapine induced OC symptoms and its dosage in an asymptomatic OCD patient. Tretment-emergence OC symptoms responded to increasing the doses of maintanance clomipramine treatment. CONCLUSIONS: Controlled studies are needed to investigate the dose-response or dose-severity relationships between OCD and atypical antipsychotics.     

Behavioral inhibition and obsessive-compulsive disorder

Behavioral inhibition is frequently cited as a vulnerability factor for development of anxiety. However, few studies have examined the unique relationship between behavioral inhibition and obsessive-compulsive disorder (OCD). Therefore, the current study addressed the relationship between behavioral inhibition and OCD in a number of ways. In a large unselected student sample, frequency of current OC symptoms was significantly correlated with retrospective self-reports of total levels of childhood behavioral inhibition. In addition, frequency of current OC symptoms was also significantly correlated with both social and nonsocial components of behavioral inhibition. Further, there was evidence for a unique relationship between behavioral inhibition and OC symptoms beyond the relationship of behavioral inhibition and social anxiety. In addition, results showed that reports of childhood levels of behavioral inhibition significantly predicted levels of OCD symptoms in adulthood. Finally, preliminary evidence suggested that behavioral inhibition may be more strongly associated with some types of OC symptoms than others, and that overprotective parenting may moderate the impact of behavioral inhibition on OC symptoms. The current findings suggest the utility of additional research examining the role of behavioral inhibition in the etiology of OCD.     

Obsessive-compulsive disorder and serotonin: is there a connection?

Reports of the antiobsessional efficacy of clomipramine have led to a "serotonin hypothesis" of obsessive-compulsive disorder (OCD). To test this hypothesis, 16 outpatients with DSM-III OCD were studied using several measures of serotonergic function. Platelet 3H-imipramine binding and serotonin uptake were not significantly different between the OCD patients and a normal, age-matched control group. The level of the metabolite 5-hydroxyindoleacetic acid (5-HIAA) in cerebrospinal fluid (CSF) was significantly higher in a small cohort of obsessionals compared with healthy volunteers, possibly reflecting increased brain serotonin turnover. In a direct test of the role of serotonin uptake in clomipramine's antiobsessional effects, the serotonin uptake inhibitor zimelidine was compared with the noradrenergic uptake inhibitor desipramine in a double-blind, controlled study. Zimelidine reduced CSF 5-HIAA, but was clinically ineffective in this group. Desipramine had weak but significant clinical effects. Nonresponders to zimelidine or desipramine improved significantly during a subsequent double blind trial of clomipramine. These findings demonstrate that pharmacological blockade of serotonin reuptake alone is not sufficient for an antiobsessional response.     

Serotonergic responsivity in obsessive-compulsive disorder. Comparison of patients and healthy controls

To examine the "serotonin hypothesis" of obsessive-compulsive disorder (OCD), we studied the behavioral and neuroendocrine effects of metachlorophenylpiperazine (mCPP), a serotonergic agonist, in patients with OCD and healthy controls. Twelve patients and 20 controls were given a single dose of 0.5 mg/kg of mCPP, administered orally under double-blind, placebo-controlled, random-assignment conditions. Following mCPP, but not following placebo, patients with OCD experienced a transient but marked exacerbation of obsessive-compulsive symptoms. Moreover, compared with healthy controls, patients exhibited greater other behavioral (but not endocrinologic or thermal) changes after mCPP. These findings are consistent with a special role for the neurotransmitter serotonin in OCD psychopathology.     

Early response with clomipramine in obsessive compulsive disorder--a placebo controlled study

1. Clomipramine has been found to be effective in the treatment of obsessive compulsive disorder (OCD) in nine placebo controlled studies whereas other conventional antidepressants lacking 5-HT reuptake inhibiting properties do not appear to be effective. 2. The placebo response rate in OCD is very low as is seen in the placebo controlled study of the efficacy of clomipramine 75mg in 14 patients suffering from OCD reported here. 3. Response appears early in treatment when compared with response of depression to antidepressants.     

Dopamine blocking activity of clomipramine in patients with obsessive-compulsive disorder.

While many data suggest that Obsessive-Compulsive Disorder (OCD) is an illness accompanied by dysregulation of the serotonergic system, interesting clinical evidence and animal studies also suggest possible dysregulation of the dopaminergic (DA) system. In order to determine whether clomipramine (CMI), an antiobsessional agent, is capable of altering DA function, we performed a neuroleptic radioreceptor assay (NRRA) on plasma samples from OCD patients before and after treatment in a double-blind, placebo controlled trial of CMI. CMI produced mild but significant DA D-2 receptor binding activity in an in vitro assay. The degree of dopamine binding activity did not correlate with clinical response to clomipramine. Because it has been suggested that another drug with antiobsessional efficacy, fluoxetine, may also have dopamine blocking properties, it may be speculated that antidopaminergic activity in combination with serotonergic effects is involved in antiobsessional activity of effective agents for some patients.     

Anxiogenic effects of m-CPP in patients with panic disorder: comparison to caffeine's anxiogenic effects.

The behavioral and neuroendocrine effects of meta-chlorophenylpiperazine (m-CPP), a serotonergic agonist, were compared with the effects of caffeine, an adenosine antagonist, in panic disorder patients. Patients with panic disorder were given single oral doses of 0.5 mg/kg m-CPP, 480 mg caffeine, and placebo on separate days under double-blind conditions. Both m-CPP and caffeine had significantly greater anxiogenic and panic-inducing effects than placebo, although caffeine produced nonsignificantly greater increases on all anxiety rating scales than m-CPP. Both m-CPP and caffeine produced significant equivalent increases in plasma cortisol concentrations, but only m-CPP produced plasma prolactin increases. These findings provide further evidence implicating both the serotonergic and adenosinergic receptor systems in the neurobiology of panic disorder.     

Enhancement of CO2-induced anxiety in healthy volunteers with the serotonin antagonist metergoline.

OBJECTIVE: The mechanism of action of CO2-induced anxiety is unknown and has been little studied. The authors studied healthy volunteers for the possible influence of serotonin (5-HT) on CO2-induced anxiety. METHOD: Fourteen healthy volunteers received two vital capacity inhalations each of 35% CO2 and of air, preceded once by placebo and once by the 5-HT antagonist metergoline in a double-blind, randomized crossover design. RESULTS: Mean National Institute of Mental Health self-rating anxiety subscale scores increased nonsignificantly after CO2 inhalation; this effect was significantly enhanced by the administration of metergoline. CONCLUSIONS: The authors hypothesize that 5-HT may inhibit CO2-induced anxiety, a function that is lessened by metergoline.     

Lack of effects on core obsessive-compulsive symptoms of tryptophan depletion during symptom provocation in remitted obsessive-compulsive disorder patients.

BACKGROUND: Pharmacological evidence support that enhancement of serotonin (5-HT) neurotransmission is critical for treatment efficacy in obsessive-compulsive disorder (OCD). Surprisingly, acute tryptophan depletion (ATD), a procedure known to reduce 5-HT neurotransmission, carried out in remitted OCD patients on selective serotonin reuptake inhibitors (SSRIs) failed to worsen obsessive-compulsive (OC) symptoms. We hypothesized that the putative symptom exacerbation resulting from ATD would only be observed during symptom provocation but not at rest. METHODS: Double-blind placebo-controlled ATD study conducted in 16 OCD patients with stable improvement under either SSRI (n = 8) or specialized cognitive behavior therapy alone (n = 8), coupled with gradual symptom provocation, performed 5 hours after drink ingestion. RESULTS: Acute tryptophan depletion markedly reduced total and free plasma tryptophan levels but did not significantly increase obsessions or compulsions at rest or following symptom provocation. However, subjective distress in response to triggering situations was significantly higher during ATD; significant mood lowering was also present during ATD. CONCLUSIONS: These results are consistent with the view that relapses in OC core symptoms in remitted OCD patients may not depend solely on short-term changes in presynaptic 5-HT availability. In contrast to its apparent lack of effect on core OC symptoms, ATD affected the patient's mood and distress level resulting from provocation.     

Serotonergic dissection of obsessive compulsive symptoms: a challenge study with m-chlorophenylpiperazine and sumatriptan

We have conducted a pharmacological challenge experiment in 10 medication-free obsessive compulsive (OC) disorder (OCD) patients. We used a placebo-controlled paradigm for m-chlorophenylpiperazine (mCPP) and sumatriptan challenges. Endocrine, physiological and behavioral variables were assessed at baseline and over a 3-hour period after the challenge. Both cortisol and prolactin were significantly elevated in OCD patients following mCPP administration. Both mCPP and sumatriptan caused significant OC symptom exacerbation with the response to sumatriptan being more robust. We conclude that the 5-HT(1Dbeta) receptor may play a role in the pathophysiology of OCD.     

Controlled comparisons of clomipramine and fluoxetine in the treatment of obsessive-compulsive disorder. Behavioral and biological results

Treatment with fluoxetine hydrochloride was compared with treatment with clomipramine hydrochloride in two groups of patients with obsessive-compulsive disorder using two different experimental designs. In the first group of 11 patients with obsessive-compulsive disorder studied using a randomized, double-blind, crossover design, treatment with fluoxetine for 10 weeks was found to produce therapeutic effects similar to treatment with clomipramine for 10 weeks. There were significantly fewer total side effects reported during fluoxetine than clomipramine treatment. Drug tapering and placebo substitution in the 4-week crossover interval phase led to substantial relapses in obsessive-compulsive disorder symptoms and depression. Furthermore, responses to the second drug took as long to occur as responses to the first drug, although both drugs are thought to act by a common mechanism, serotonin uptake inhibition. A second group of 21 patients with obsessive-compulsive disorder that had been previously stabilized on clomipramine treatment with at least partial benefit were crossed over to fluoxetine treatment in a double-blind fashion. After 10 weeks of fluoxetine administration, most patients manifested behavioral rating scores of obsessive-compulsive disorder and depressive symptoms that were comparable with precrossover ratings completed during clomipramine treatment. A significant exacerbation in obsessive-compulsive disorder and depression ratings as well as a similar lag in therapeutic efficacy were also noted in this second cohort of patients with obsessive-compulsive disorder. Platelet 5-HT concentrations were reduced 95% during both clomipramine and fluoxetine treatment periods. These results suggest that fluoxetine may represent a viable alternative to clomipramine in the treatment of obsessive-compulsive disorder, although further studies with larger sample sizes are needed.