Neuroleptic-induced decrease in plasma homovanillic acid and antipsychotic activity in schizophrenic patients

A Highly Selective Implantable Electrochemical Fiber Sensor for Real-Time Monitoring of Blood Homovanillic Acid

Homovanillic acid (HVA) is a major dopamine metabolite, and blood HVA is considered as central nervous system (CNS) dopamine biomarker, which reflects the progression of dopamine-associated CNS diseases and the behavioral response to therapeutic drugs. However, facing blood various active substances interference, particularly structurally similar catecholamines and their metabolites, real-time and accurate monitoring of blood HVA remains a challenge. Herein, a highly selective implantable electrochemical fiber sensor based on a molecularly imprinted polymer is reported to accurately monitor HVA in vivo. The sensor exhibits high selectivity, with a response intensity to HVA 12.6 times greater than that of catecholamines and their metabolites, achieving 97.8% accuracy in vivo. The sensor injected into the rat caudal vein tracked the real-time changes of blood HVA, which paralleled the brain dopamine fluctuations and indicated the behavioral response to dopamine increase. This study provides a universal design strategy for improving the selectivity of implantable electrochemical sensors.

Discovery of novel phenothiazine derivatives as new agrochemical alternatives for treating plant viral diseases

BACKGROUND

Plant viral diseases, namely 'plant cancer', are extremely difficult to control. Even worse, few antiviral agents can effectively control and totally block viral infection. There is an urgent need to explore and discover novel agrochemicals with high activity and a unique mode of action to manage these refractory diseases.

RESULTS

Forty-one new phenothiazine derivatives were prepared and their inhibitory activity against tobacco mosaic virus (TMV) was assessed. Compound A8 had the highest protective activity against TMV, with a half-maximal effective concentration (EC50 ) of 115.67 μg/mL, which was significantly better than that of the positive controls ningnanmycin (271.28 μg/mL) and ribavirin (557.47 μg/mL). Biochemical assays demonstrated that compound A8 could inhibit TMV replication by disrupting TMV self-assembly, but also enabled the tobacco plant to enhance its defense potency by increasing the activities of various defense enzymes.

CONCLUSION

In this study, novel phenothiazine derivatives were elaborately fabricated and showed remarkable anti-TMV behavior that possessed the dual-action mechanisms of inhibiting TMV assembly and invoking the defense responses of tobacco plants. Moreover, new agrochemical alternatives based on phenothiazine were assessed for their antiviral activities and showed extended agricultural application. © 2023 Society of Chemical Industry.

Presynaptic vesicular accumulation is required for antipsychotic efficacy in psychotic-like rats

BACKGROUND

The therapeutic effects of antipsychotic drugs (APDs) are mainly attributed to their postsynaptic inhibitory functions on the dopamine D2 receptor, which, however, cannot explain the delayed onset of full therapeutic efficacy. It was previously shown that APDs accumulate in presynaptic vesicles during chronic treatment and are released like neurotransmitters in an activity-dependent manner triggering an auto-inhibitory feedback mechanism. Although closely mirroring therapeutic action onset, the functional consequence of the APD accumulation process remained unclear.

AIMS

Here we tested whether the accumulation of the APD haloperidol (HAL) is required for full therapeutic action in psychotic-like rats.

METHODS

We designed a HAL analog compound (HAL-F), which lacks the accumulation property of HAL, but retains its postsynaptic inhibitory action on dopamine D2 receptors.

RESULTS/OUTCOMES

By perfusing LysoTracker fluorophore-stained cultured hippocampal neurons, we confirmed the accumulation of HAL and the non-accumulation of HAL-F. In an amphetamine hypersensitization psychosis-like model in rats, we found that subchronic intracerebroventricularly delivered HAL (0.1 mg/kg/day), but not HAL-F (0.3-1.5 mg/kg/day), attenuates psychotic-like behavior in rats.

CONCLUSIONS/INTERPRETATION

These findings suggest the presynaptic accumulation of HAL may serve as an essential prerequisite for its full antipsychotic action and may explain the time course of APD action. Targeting accumulation properties of APDs may, thus, become a new strategy to improve APD action.

Plasma monoamines change under dopamine supersensitivity psychosis in patients with schizophrenia: A comparison with first-episode psychosis

BACKGROUND

Patients with first-episode psychosis respond well to initial antipsychotic treatment, but among patients experiencing a relapse of psychosis, the response rate falls to approximately 30%. The mechanism of this discrepancy has not been clarified, but the development of dopamine supersensitivity psychosis with the underlying up-regulation of post-synaptic dopamine D2 receptors could be involved in this lesser response. It is uncertain whether elevated dopamine synthesis and release occurs in patients with dopamine supersensitivity psychosis, in contrast to those with first-episode psychosis.

PATIENTS AND METHODS

We examined a first-episode psychosis group (n=6) and a chronic schizophrenia group, i.e. patients experiencing relapse (n=23) including those who relapsed due to dopamine supersensitivity psychosis (n=18). Following the initiation of treatment, we measured the patients' blood concentrations of homovanillic acid and 3-methoxy-4-hydroxyphenylglycol at two weeks and four weeks after the baseline measurements.

RESULTS

The first-episode psychosis group tended to show decreased homovanillic acid, accompanied by an improvement of symptoms. The chronic schizophrenia group showed no alteration of homovanillic acid or 3-methoxy-4-hydroxyphenylglycol over the treatment period. These results were the same in the dopamine supersensitivity psychosis patients alone.

CONCLUSIONS

Our findings suggest that unlike first-episode psychosis, the release of dopamine from presynaptic neurons did not increase in relapse episodes in the patients with dopamine supersensitivity psychosis. This indirectly indicates that the development of supersensitivity of post-synapse dopamine D2 receptor is involved in relapse in dopamine supersensitivity psychosis patients.

Profiles of the pharmacologic response of positive and negative symptoms in schizophrenia

The delineation of the symptoms of schizophrenia into positive and negative types has been an important trend in psychiatric research over the past decade. This approach reflects renewed interests in clinical description and in developing etiologic hypotheses. The responsivity of positive and negative symptoms to neuroleptic and other pharmacotherapies, an issue of considerable clinical and research importance, however, remain in controversy.

We have observed that double-blind fluphenazine administration to 19 schizophrenic inpatients who had been maintained free from neuroleptic treatment for an extended period of time resulted in significant decreases in both positive as well as negative symptoms. The time course of symptom change differed, however, and the change in symptoms was not correlated, suggesting that the underlying pathophysiologies of positive and negative symptoms are only partially overlapping. The relative balance between positive and negative symptoms in individual patients, a putative schizophrenia trait characteristic, was found to be significantly altered by neuroleptic treatment, raising questions about the reliability of this classification approach.

In longitudinal studies in which plasma levels of the dopamine metabolite, homovanillic acid (HVA), were measured, change in negative symptoms associated with neuroleptic withdrawal and treatment were correlated, respectively, with changes in levels of plasma HVA. These data further support a relationship between negative symptoms and dopaminergic function. In addition to neuroleptic-induced reductions in negative symptoms, the augmentation of neuroleptic antipsychotic effects by the triazolobenzodiazepine, alprazolam, includes improvement in negative and positive symptoms in responsive patients.

These data including longitudinal studies of individual patients suggest that negative as well as positive symptoms respond to pharmacologic intervention. The clinical and research implications of these findings are discussed.

Antidopaminergic medication in healthy subjects provokes subjective and objective mental impairments tightly correlated with perturbation of biogenic monoamine metabolism and prolactin secretion

OBJECTIVES

Off-label prescription of antipsychotics to patients without psychotic symptoms has become a routine matter for many psychiatrists and also some general practitioners. Nonetheless, little is known about the possibly detrimental effects of antidopaminergic medications on general psychopathology, subjective mental state, or a possible association with physiological parameters in nonpsychotic individuals.

METHODS

In this randomized, single-blinded study, groups of healthy volunteers (n=18) received low doses of reserpine, aripiprazole, haloperidol, or placebo on 7 successive days. Relevant physiological parameters (plasma prolactin, concentrations of catecholamine metabolites in plasma, and 24-hour urine) and each subject's mental state (Positive and Negative Syndrome Scale, Hamilton Rating Scale for Depression, visual analogue scale, Beck Depression Inventory II) were assessed at the start and end of the trial.

RESULTS

Of the three active treatments, only reserpine caused a significant increase in some plasma- and urine-catecholamine metabolites, but all three medications evoked objective and subjective changes in general psychopathology scores, which correlated with individual increases in plasma homovanillic acid concentrations. Both objective and subjective impairments were significantly more pronounced in the subgroup with greatest increase of plasma prolactin. Subjects experiencing the most pronounced side effects under haloperidol, which compelled them to drop out, showed significantly higher prolactin concentration increases than those who tolerated haloperidol well.

CONCLUSION

We found consistent associations between altered markers of dopamine transmission and several objective and subjective mental impairments in healthy volunteers after 1 week's treatment with antidopaminergic medications. These findings should draw attention to a more intensive risk-benefit evaluation in cases of off-label prescription of antipsychotic medications.

Relationships between serum brain-derived neurotrophic factor, plasma catecholamine metabolites, cytokines, cognitive function and clinical symptoms in Japanese patients with chronic schizophrenia treated with atypical antipsychotic monotherapy

OBJECTIVES

Catecholamines, brain-derived neurotrophic factor (BDNF) and cytokines may be involved in the pathophysiology of schizophrenia. The aim of this study was to examine the associations between serum BDNF levels, plasma catecholamine metablolites, cytokines and the cognitive functions of patients with schizophrenia treated with atypical antipsychotic monotherapy.

METHODS

One hundred and forty-six patients with schizophrenia and 51 age- and sex-matched healthy controls were examined for peripheral biological markers and neurocognitive test.

RESULTS

There were positive correlations between serum BDNF levels and scores for verbal memory and attention and processing speed as well as between serum BDNF levels and negative symptoms. Furthermore, there was a negative correlation between the plasma homovanillic acid (HVA) level and motor function and a positive correlation between the plasma 3-methoxy-4-hydroxyphenylglycol (MHPG) level and attention and processing speed. There were no significant correlations between interleukin-6 or tumour necrosis factor alpha and cognitive function. Moreover, there were no significant correlations between the plasma levels of HVA, MHPG, cytokines and clinical symptoms.

CONCLUSIONS

Serum BDNF levels are positively related to the impairment of verbal memory and attention, plasma HVA levels are positively related to motor function, and plasma MHPG levels are positively related to attention in patients with schizophrenia.

Blood Biomarkers Predict the Cognitive Effects of Aripiprazole in Patients with Acute Schizophrenia

Aripiprazole has been reported to exert variable effects on cognitive function in patients with schizophrenia. Therefore, in the present study, we evaluated biological markers, clinical data, and psychiatric symptoms in order to identify factors that influence cognitive function in patients with schizophrenia undergoing aripiprazole treatment. We evaluated cognitive function in 51 patients with schizophrenia using Brief Assessment of Cognition in Schizophrenia (BACS), as well as background information, psychiatric symptoms, plasma catecholamine metabolites-homovanillic acid (HVA), 3-methoxy-4-hydroxyphenylglycol (MHPG)-, and serum brain-derived neurotrophic factor (BDNF). Multivariate analyses were performed in order to identify factors independently associated with cognitive function. Brain-derived neurotrophic factor levels, number of hospitalizations, and MHPG levels were associated with verbal memory and learning. Total hospitalization period and MHPG levels were associated with working memory. Age at first hospitalization and education were associated with motor speed. The number of hospital admissions, Positive and Negative Syndrome Scale negative subscale scores (PANSS-N), MHPG levels, BDNF levels, and Drug-Induced Extrapyramidal Symptoms Scale (DIEPSS) scores were associated with verbal fluency. Homovanillic acid and MHPG levels, duration of illness, and PANSS-N scores were associated with attention and processing speed. Brain-derived neurotrophic factor and MHPG levels were associated with executive function. These results suggest that treatment of psychiatric symptoms and cognitive dysfunction may be improved in patients treated with aripiprazole by controlling for these contributing factors.

Clonazepam improves dopamine supersensitivity in a schizophrenia patient: a case report

Dopamine supersensitivity is an important consideration for assessing treatment-resistant schizophrenia. The emergence of dopamine supersensitivity might be related to upregulation of dopamine D2 receptor, which engenders tolerance to antipsychotics, rebound psychosis, and tardive dyskinesia (TD). A 24-year-old man with a history of treatment-resistant schizophrenia was hospitalized for treatment of bone fracture sustained during a suicide attempt. After the operation, his clinical symptoms implied malignant catatonia. The patient discontinued antipsychotics without rebound psychosis under clonazepam treatment. His psychotic symptoms were controlled further with 24 mg/day aripiprazole without relapse or worsening. Clonazepam might be an effective option for the management of dopamine supersensitivity psychosis (DSP).

Schizophrenia: the role of sleep and circadian rhythms in regulating dopamine and psychosis

Schizophrenia has long been associated with abnormalities in circadian rhythms and sleep. Up until now, there have been no thorough reviews of the potential mechanisms behind the myriad of circadian and sleep abnormalities observed in schizophrenia and psychosis. We present evidence of sleep playing an important role in psychosis predominantly mediated by dopaminergic pathways. A synthesis of both human and animal experimental work suggests that the interplay between sleep and dopamine is important in the generation and maintenance of psychosis. In particular, both animal and human data point to sleep disruption increasing dopamine release and sensitivity. Furthermore, elevated dopamine levels disrupt sleep and circadian rhythms. The synthesis of knowledge suggests that circadian rhythms, dopamine dysregulation, and psychosis are intricately linked. This suggests that treatment of circadian disturbance may be a useful target in improving the lives and symptoms of patients with schizophrenia.

Paradox of schizophrenia genetics: is a paradigm shift occurring?

BACKGROUND

Genetic research of schizophrenia (SCZ) based on the nuclear genome model (NGM) has been one of the most active areas in psychiatry for the past two decades. Although this effort is ongoing, the current situation of the molecular genetics of SCZ seems disappointing or rather perplexing. Furthermore, a prominent discrepancy between persistence of the disease at a relatively high prevalence and a low reproductive fitness of patients creates a paradox. Heterozygote advantage works to sustain the frequency of a putative susceptibility gene in the mitochondrial genome model (MGM) but not in the NGM.

METHODS

We deduced a criterion that every nuclear susceptibility gene for SCZ should fulfill for the persistence of the disease under general assumptions of the multifactorial threshold model. SCZ-associated variants listed in the top 45 in the SZGene Database (the version of the 23rd December, 2011) were selected, and the distribution of the genes that could meet or do not meet the criterion was surveyed.

RESULTS

19 SCZ-associated variants that do not meet the criterion are located outside the regions where the SCZ-associated variants that could meet the criterion are located. Since a SCZ-associated variant that does not meet the criterion cannot be a susceptibility gene, but instead must be a protective gene, it should be linked to a susceptibility gene in the NGM, which is contrary to these results. On the other hand, every protective gene on any chromosome can be associated with SCZ in the MGM. Based on the MGM we propose a new hypothesis that assumes brain-specific antioxidant defenses in which trans-synaptic activations of dopamine- and N-methyl-d-aspartate-receptors are involved. Most of the ten predictions of this hypothesis seem to accord with the major epidemiological facts and the results of association studies to date.

CONCLUSION

The central paradox of SCZ genetics and the results of association studies to date argue against the NGM, and in its place the MGM is emerging as a viable option to account for genomic and pathophysiological research findings involving SCZ.

Dopamine system dysregulation by the hippocampus: implications for the pathophysiology and treatment of schizophrenia

For decades, the predominant hypothesis of schizophrenia centered on dysfunctions of the dopamine system. However, recent evidence now suggests that the dopamine system may be "normal" in its configuration, but instead is regulated abnormally by modulatory processes. Convergent studies in animals and in humans have now focused on the hippocampus as a central component in the generation of psychosis and possibly other symptom states in schizophrenia. Thus, activity in the ventral hippocampus has been shown to regulate dopamine neuron responsivity by controlling the number of dopamine neurons that can be phasically activated by stimuli. In this way, this structure determines the gain of the dopamine signal in response to stimuli. However, in schizophrenia, the hippocampus appears to be hyper-active, possibly due to attenuation of function of inhibitory interneurons. As a result, the dopamine system is driven into an overly responsive state. Current medications have focused on blockade of overstimulated dopamine receptors; however, this now appears to be several synapses downstream from the pathological antecedent. Therapeutic approaches that focus on normalizing hippocampal function may prove to be more effective treatment avenues for the schizophrenia patient.

Dopamine, Paranormal Belief, and the Detection of Meaningful Stimuli

Dopamine (DA) is suggested to improve perceptual and cognitive decisions by increasing the signal-to-noise ratio. Somewhat paradoxically, a hyperdopaminergia (arguably more accentuated in the right hemisphere) has also been implied in the genesis of unusual experiences such as hallucinations and paranormal thought. To test these opposing assumptions, we used two lateralized decision tasks, one with lexical (tapping left-hemisphere functions), the other with facial stimuli (tapping right-hemisphere functions). Participants were 40 healthy right-handed men, of whom 20 reported unusual, “paranormal” experiences and beliefs (“believers”), whereas the remaining participants were unexperienced and critical (“skeptics”). In a between-subject design, levodopa (200 mg) or placebo administration was balanced between belief groups (double-blind procedure). For each task and visual field, we calculated sensitivity (d′) and response tendency (criterion) derived from signal detection theory. Results showed the typical right visual field advantage for the lexical decision task and a higher d′ for verbal than facial stimuli. For the skeptics, d′ was lower in the levodopa than in the placebo group. Criterion analyses revealed that believers favored false alarms over misses, whereas skeptics displayed the opposite preference. Unexpectedly, under levodopa, these decision preferences were lower in both groups. We thus infer that levodopa (1) decreases sensitivity in perceptual–cognitive decisions, but only in skeptics, and (2) makes skeptics less and believers slightly more conservative. These results stand at odd to the common view that DA generally improves signal-to-noise ratios. Paranormal ideation seems an important personality dimension and should be assessed in investigations on the detection of signals in noise.

Review: The biological basis of antipsychotic response in schizophrenia

Schizophrenia is a severe mental illness affecting approximately 1% of the population worldwide. Antipsychotic drugs are effective in symptom control in up to two-thirds of patients, but in at least one-third of patients the response is poor. The reason for this is not clear, but one possibility is that good and poor responders have different neurochemical pathologies, and may therefore benefit from different treatment approaches. In this selective review we summarise research findings investigating the biological differences between patients with schizophrenia who show a good or a poor response to treatment with antipsychotic drugs.

GABA and homovanillic acid in the plasma of Schizophrenic and bipolar I patients

We have determined the plasma (p) concentration of gamma-aminobutyric acid (GABA) and the dopamine metabolite homovanillic acid (HVA), and the pHVA/pGABA ratio in schizophrenic and bipolar patients. The research was undertaken in a geographic area with an ethnically homogeneous population. The HVA plasma concentrations were significantly elevated in the schizophrenic patients compared to the bipolar patients. The levels of pGABA was significantly lower in the two groups of patients compared to the control group, while the pHVA/pGABA ratio was significantly greater in the both groups of patients compared to the controls. As the levels of pHVA and pGABA are partially under genetic control it is better to compare their concentrations within an homogeneous population. The values of the ratio pHVA/pGABA are compatible with the idea of an abnormal dopamine-GABA interaction in schizophrenic and bipolar patients. The pHVA/pGABA ratio may be a good peripheral marker in psychiatric research.

Plasma homovanillic acid differences in clinical subgroups of first episode schizophrenic patients

This study evaluates the relationship between plasma homovanillic acid (pHVA) levels, which have been used to study the role of central dopamine in schizophrenia, and the positive/negative syndrome in first episode schizophrenic patients before and after antipsychotic treatment. Forty neuroleptic-naive first episode schizophrenic patients were monitored at baseline and on days 7, 14 and 28. Clinical status was evaluated with the Scale for the Assessment of Positive Symptoms (SAPS), the Scale for the Assessment of Negative Symptoms (SANS), and the Brief Psychotic Rating Scale. Plasma HVA levels were also measured. Patients were divided into predominantly positive or negative syndrome groups by subtracting SAPS from SANS scores, at baseline. A healthy control group was also enrolled. Schizophrenic patients as a group had significantly higher pHVA levels than controls at baseline (20.50+/-11.85 vs. 13.04+/-7.22 ng/ml). Moreover, 12 predominantly negative syndrome patients had similar mean baseline pHVA levels (21.30+/-12.36 ng/ml) to those of 28 predominantly positive syndrome patients (19.40+/-11.33 ng/ml). During follow-up, there was a different evolution of pHVA levels in the predominantly positive syndrome group than in the predominantly negative syndrome group, with a significantly greater global reduction of pHVA levels in the former. Although both groups showed clinical improvement following 4 weeks of treatment with risperidone, pHVA levels at endpoint were lower (13.29+/-5.91 ng/ml) than at baseline in patients in the predominantly positive syndrome group, while among those in the predominantly negative syndrome group there was no difference in pHVA levels before and after treatment (21.02+/-13.06 ng/ml). The different pHVA level profiles observed in predominantly positive and negative syndrome first episode patients after 4 weeks of treatment with risperidone suggest that each syndrome may have a different underlying neurobiology.

Schizotypy and pseudoneglect: a critical update on theories of hemispheric asymmetries

INTRODUCTION

Positive schizotypy has been associated with a leftward spatial bias (pseudoneglect) in different tasks and populations. We tested whether this relationship (1) can be observed for two different hemispatial tasks in the same participants, and (2) is specific to positive schizotypy.

METHODS

Forty right-handed men performed a conventional line bisection task and a whole-body movement task. In the latter task, participants were presented with illuminated target locations on the floor, and had to visit the remembered locations (equal number in right and left hemispace) after a short time interval. We assessed side preferences in both tasks. Positive schizotypy, negative schizotypy, and cognitive disorganisation were assessed with a validated self-report questionnaire.

RESULTS

Irrespective of schizotypy, pseudoneglect was observed in both tasks. We found a rightward bisection and walking bias as a function of positive schizotypy, and also as a function of cognitive disorganisation for walking initiation.

DISCUSSION

This unexpected finding resulted in a review of hemispheric asymmetry for function in schizotypy, and in the discussion of potential variables that might account for the present discrepancy. We suggest that different schizotypy questionnaires and their presentation mode might be a potential contributor to the opposite findings in the literature.

Plasma homovanillic acid levels in schizophrenic patients: correlation with negative symptoms

The relation between changes in the levels of plasma homovanillic acid (pHVA) and clinical evolution during neuroleptic treatment of schizophrenic patients has not been satisfactorily characterized, as a number of conflicting findings have been reported. Significant correlations have generally been found using the assessment of positive symptoms as an index of clinical outcome. Nevertheless, attempts to correlate pHVA concentrations with negative symptoms have yielded contradictory results. With a view to evaluating if different responses in negative symptoms are associated with distinct pHVA profiles, we examined the levels of pHVA in 46 neuroleptic-free schizophrenic patients and in these patients after neuroleptic treatment. Negative and positive symptoms were also addressed before and after treatment. Our results reveal that at least two classes of negative symptoms exist; the clinical evolution of the first class of negative symptoms parallels that of positive symptoms, and clinical improvement correlates with reduced dopaminergic activity. In contrast, in the second class, reduced dopaminergic activity is associated with a further deterioration of negative symptoms. These findings corroborate the heterogeneity of negative symptoms and may contribute to a better definition of endophenotypes in the schizophrenic syndrome.

Inter- and intra-individual variability in the levels of plasma homovanillic acid in schizophrenic patients

BACKGROUND

Changes in the levels of homovanillic acid in blood plasma (pHVA) may reflect changes which occur in the brain. In healthy individuals, this concentration of pHVA is stable over time.

METHODS

Over the course of one month, we studied 98 acute schizophrenic patients who had not been taking any medication but were administered neuroleptics upon hospital admission, together with 23 chronic schizophrenic patients on long-term treatment from whom medication was withdrawn. Blood samples were taken at regular intervals from each individual and the concentration of plasma homovanillic acid was measured.

RESULTS

We found relative stable values of pHVA with an intraclass correlation coefficient of 0.363 in acute patients and 0.638 (p<0.0001) in chronic patients, although no differences were found in mean values (13.79 and 14.18 microg/L, respectively) or in the variation range (7.20 to 26.7 microg/L and 6.96 to 29.96 microg/L respectively). The index of individuality was calculated to be 1.36 in acute patients and 0.74 in chronic patients.

CONCLUSIONS

Despite the wide range of values in the concentration of pHVA and the presence of pharmacological stimuli, we found a certain reproducibility in the levels of this dopamine metabolite. These findings are consistent with the idea that the dopaminergic activity is characterized by a constitutive value which would be under genetic control. The higher stability observed in chronic patients may reflect a weaker, age-related dopaminergic plasticity; conversely, it may indicate that a lack of plasticity in response to a pharmacological stimulus may be an indicator of poorer prognosis.

Correlation Between Plasma Homovanillic Acid Levels and the Response to Atypical Antipsychotics in Male Patients With Schizophrenia

OBJECTIVE

The authors investigated the effects of atypical antipsychotic drugs-olanzapine, perospirone, and quetiapine-on plasma homovanillic acid (pHVA) in male patients with chronic schizophrenia.

METHODS

In this prospective, open-label study, the subjects were 30 inpatients who were diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders, 4th edition, criteria for schizophrenia. The authors switched patients from typical antipsychotic drugs to olanzapine, perospirone, or quetiapine. Each patient gave informed consent for the research. pHVA was assessed before and after switching medications.

RESULTS

After the switch, the authors found a significant improvement in psychotic symptoms, nonsignificant improvement in extrapyramidal symptoms, and a nonsignificant reduction in pHVA. In addition, the baseline pHVA correlated positively with the score changes from baseline in the Brief Psychiatric Rating Scale (BPRS) total, positive, and negative symptoms in the group with a whole sample and in the olanzapine-treated group, and with the score changes in the BPRS total and positive symptoms in the quetiapine-treated group.

CONCLUSION

Our findings indicated that the preswitching pHVA levels could be used to predict changes in the psychotic symptoms of male patients with chronic schizophrenia when switching to atypical antipsychotic drugs.

Levodopa reverses gait asymmetries related to anhedonia and magical ideation

Animals and men turn preferentially away from the hemisphere with the more active dopamine (DA) system. Consistent with the idea of a right-hemispheric hyperdopaminergia in schizophrenia, a leftsided turning bias was described for unmedicated psychotic patients. We investigated the modulating role of DA and schizophrenia-like thought on whole-body turns in a controlled double-blind study. The number of veers to either side when walking blindfolded straight ahead (20 meter) was assessed in 40 healthy righthanded men (20 men received levodopa, the remaining participants placebo). Side preferences were analyzed in terms of individuals' positive (Magical Ideation, MI) and negative (Physical Anhedonia, PhysAn) schizotypal features. In the placebo group, increasing MI scores were related to increasing left-sided veering and increasing PhysAn scores were related to increasing right-sided veering. In the levodopa group, this relationship between preferred veering side and type of schizotypy was reversed. The finding in the placebo group suggests an association between MI and a relative right-hemispheric hyperdopaminergia. Unexpectedly, levodopa did not enhance this veering bias, but reversed it, suggesting that psychosis-protective mechanisms exist in the healthy positive "schizotypic" brain. Also unexpectedly, levodopa made "anhedonics" veer like "magics" after placebo, suggesting that DA agonists suppress negative schizotypal symptoms.

Nonstereotyped responding in positive schizotypy after a single dose of levodopa

Stereotyped behavior and left-sided orientation biases, associated with the dopamine (DA) system, were observed in populations of the schizophrenia spectrum disorders. We investigated whether heightened DA concentrations influence both side biases and stereotyped responding in a visuo-motor computer task, in which 90, 180, and 270 degrees rotated objects had to be brought into a target position. To account for the role of the schizophrenia spectrum, task performance was also analyzed as a function of healthy participants' high or low magical ideation (MI), a positive schizotypal feature. The first 36 participants (20 women) remained substance free. In a second sample, 20 men received levodopa and 20 men a placebo in a double-blind procedure. Results showed that high MI scorers responded more stereotyped than low MI scorers, without being specifically biased towards the left side. Rotation preferences toward one or the other side made high MI scorers less flexible for objects efficiently to be rotated into the opposite direction. This inflexibility may reflect impaired left hemisphere functioning. Unexpectedly, in the levodopa group, high MI scorers performed superior to low MI scorers. Since DA actions appear to follow an inverted U-shape function, the 'low' performing high MI scorers profited from the enhanced DA availability. Our observation in the levodopa group points to a dissociation between schizotypy and schizophrenia: while cognitive improvement in schizophrenia can occur after treatment with atypical neuroleptic agents, in our positive schizotypal participants a DA agonist resulted in improved task performance. This dissociation may point to protective neurochemical mechanisms preventing healthy schizotypes from developing full-blown psychotic symptoms.

Discovery and utilization of haplotypes for pharmacogenetic studies of psychotropic drug response

The treatment of seriously mentally ill patients is complicated by variability in individual response to psychotropic drugs. Some patients remain treatment refractory even after two to three therapeutic modalities. Other patients experience adverse events that range from mild discomfort, to poor compliance, to life threatening. Genaissance Pharmaceuticals is actively engaged in a candidate gene-based haplotype (HAP Marker) approach to the pharmacogenetics of drug response and adverse events. In the present article, we review reasons why HAP Markers are more useful than single nucleotide polymorphisms (SNPs) for discovering genetic correlations to clinical response. In addition, we review our approach to HAP Marker discovery, which involves discovering SNPs in the functional regions of genes by sequencing, organizing these SNPs into HAP Markers for an index population of ethnically diverse individuals and calculating population frequencies for these HAP Markers. For clinical correlations, HAP Markers are defined and correlated to clinical data using the in-house DecoGen Informatics System. This approach has clear implications for the discovery of psychiatric disease-associated genes as well as for the development of safer, more efficacious psychiatric drugs.

Detection of TOAD-64 in adult rat brain as revealed by two-dimensional protein gel electrophoresis followed by MALDI mass spectrometry possible modulatory effect of chronic haloperidol treatment

The molecular mechanisms by which antipsychotic effects are achieved remain largely elusive. Possible mechanisms include the modulation of nerve cell gene expression. The antipsychotic drug haloperidol was administered orally (1.6 mg/kg) to adult rats for 3 weeks. Protein patterns in striata and forebrains were studied by two-dimensional gel electrophoresis (2-DE). One differentially regulated protein spot was identified by matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) after trypsin digest. Turned on after devision-64 kD (TOAD-64), the identified protein, was present in all gels and, in addition, was up-regulated in the striata but not in the forebrains of the haloperidol-treated animals by 43%. It is concluded that TOAD-64, typically regarded as a marker for commitment to neuronal differentiation during fetal development, also plays a role in adult rat forebrain and striatum and that its concentration is possibly modulated by haloperidol treatment.

Hippocampal and cortical sensory gating in rats: effects of quinpirole microinjections in nucleus accumbens core and shell

Sensory processing disturbances, as measured in the P50/sensory gating paradigm, have been linked to aberrant auditory information processing and sensory overload in schizophrenic patients. In this paradigm, the response to the second of paired-click stimuli is attenuated by an inhibitory effect of the first stimulus. Sensory gating has been observed in most healthy human subjects and normal laboratory rats. Because mesolimbic dopamine has been implicated in other filtering disturbances such as prepulse inhibition of the acoustic startle response and given the fact that amphetamine and apomorphine have been shown to disrupt gating, this study was performed to investigate the role of mesolimbic dopamine in sensory gating. The dopamine D2 receptor agonist quinpirole (10 microg/0.5 microl) was injected bilaterally in nucleus accumbens core and shell and effects on cortical and hippocampal sensory gating were investigated. Also, effects of the dopamine D2 receptor antagonist haloperidol (0.1 mg/kg, subcutaneously) as pretreatment were studied. First, quinpirole significantly reduced both the amplitude to the first click and gating as measured in the cortex and in the hippocampus. There was a tendency for the quinpirole effects on hippocampal gating to be more pronounced in rats injected in the shell. Secondly, haloperidol did not antagonize effects of quinpirole on hippocampal parameters, whereas haloperidol pretreatment fully antagonized quinpirole effects on cortical parameters. In conclusion, gating can be significantly reduced when a dopamine agonist is specifically targeted at mesolimbic dopamine D2 receptors. However, an important consideration is that the dopaminergic effects in the present study on gating are predominantly mediated by the effects on the amplitude to the first click. This has also been suggested for systemic amphetamine injections in rats and schizophrenic patients. This casts doubt on whether dopamine receptor activation affects the putative inhibitory process between the first and the second stimulus.

Plasma homovanillic acid in untreated schizophrenia--relationship with symptomatology and sex

Plasma homovanillic acid (pHVA) concentrations are considered to reflect, in part, central dopamine metabolism and thus may be of value in assessing the role of dopamine neurotransmission in schizophrenia. Furthermore, some recent studies have suggested a relationship of pHVA with symptomatology. We have undertaken a study of pHVA in a large cohort of unmedicated DSM-IV schizophrenic patients in order to assess the relationship of pHVA to various clinical parameters. pHVA in 58 drug-free patients (10.11+/-0.52 ng/ml) was significantly elevated in comparison with 62 matched control subjects (8.77+/-0.39 ng/ml). pHVA was found to be higher in patients with a more negative syndrome. No significant correlation of pHVA with overall SAPS or SANS scores was apparent in the patients although, within the SANS subscales, a significant relationship to anhedonia-asociality was apparent. Interestingly, the male drug-free patients showed a correlation of pHVA with negative symptoms defined by SANS and several SANS subscales, while females showed no significant relationship with any SANS subscales. The results may suggest that an increased dopaminergic turnover is apparent in (male) schizophrenic patients with predominantly negative symptoms, providing some support for reports that this change in neuronal activity may be related to the neuropathological abnormalities seen in the disease, which may themselves differ between males and females. Such neuronal deficits of developmental or degenerative origin may thus result in an elevation/disinhibition of central dopamine metabolism in schizophrenia.

Plasma homovanillic acid in the prodromal phase of schizophrenia

BACKGROUND

Plasma levels of homovanillic acid (pHVA) have been used as a peripheral measure of central dopaminergic activity. Despite a large body of studies investigating pHVA in schizophrenia, little is known about pHVA in patients in the prodromal phase of the illness.

METHODS

Plasma HVA levels of 12 male outpatients meeting DSM-III-R criteria for the prodromal phase of schizophrenia at the time of blood sampling (who later developed psychotic symptoms) were compared with those of 12 normal male healthy volunteers. Task amounts in the Kraepelin arithmetic test at the time of blood sampling were compared between the prodromal patients and normal controls and were correlated with pHVA levels.

RESULTS

The prodromal patients had significantly higher pHVA levels compared with normal control subjects. The mean amount of the arithmetic task for the prodromal patients was significantly less than that for controls. In the patient group, a significant negative correlation was observed between pHVA levels and the task amounts.

CONCLUSIONS

Data from the present study indicate the presence of dopaminergic dysfunction in the prodromal stage of schizophrenia that is associated with neuropsychological impairment. Increased pHVA levels in the prodromal patients may have implications for early detection of schizophrenia.

Effects of chronic neuroleptic administration on the hypothalamo-pituitary-gonadal axis of male schizophrenics

1. The authors investigated the effects of long-term neuroleptic administration on the hypothalamo-pituitary-gonadal (HPG) axis of regularly medicated schizophrenic male patients. 2. The subjects were 56 patients who were diagnosed according to the DSM-IV criteria for schizophrenia. Each patient gave informed consent for the research involved in this study. Based on the dosages of neuroleptics, the subjects were classified into two age-matched groups: those with lower dosages (LD) and those with higher dosages (HD). 3. (1) The mean level of the blood testosterone (T) in the LD group was significantly lower than that in the normal group, although the level was within normal range. There was no significant difference in the mean level of the blood T for the HD and the normal groups, or for the HD and the LD groups. (2) There was no significant difference in the mean levels of the blood luteinizing hormone between all groups. (3) Also, there was no significant difference in the mean levels of the blood follicle-stimulating hormone between the groups. (4) The mean levels of the blood prolactin in both the LD and HD groups were significantly higher than that in the normal subjects, but there was no significant difference between the LD and HD schizophrenics. 4. Overall, these results seem to indicate that (i) in male patients with chronic schizophrenia, HPG function is impaired, and (ii) chronic neuroleptic medication stimulates the HPG axis in schizophrenic patients with impaired HPG function.

Familial transmission of risk factors in the first-degree relatives of schizophrenic people

Schizophrenia is a complex illness with multiple pathophysiologic factors that contribute to its psychopathology. One strategy to identify these factors is to observe them in isolation from each other, by characterizing their expression in the relatives of schizophrenic probands. By Mendel's second law, each genetic factor should be independently distributed in a sibship, so that each can be observed by itself, uncomplicated by the general problems of the illness. Such independently distributed phenotypes are obviously useful for genetic analyses; however, they can also be considered together, to model how various brain dysfunctions may combine to produce psychoses. In addition to a sensory gating deficit linked to the alpha 7-nicotinic acetylcholine receptor locus, schizophrenics and their families have a number of other deficits, including decreased hippocampal volume on magnetic resonance images and increased plasma levels of the dopamine metabolite homovanillic acid. Although such research is far from complete, a heuristic model combining a sensory gating deficit, decreased hippocampal neuron capacity, and increased dopaminergic neurotransmission is consonant with current understanding of the neuropsychology of schizophrenia.

Neurobiological abnormalities in the relatives of schizophrenics

The inheritance of a complex illness such as schizophrenia likely involves the segregation of genetic factors, in combination with non-genetic or environmental abnormalities. This paper reviews several family studies of biological and clinical aspects of schizophrenia, that have attempted to observe such segregation in relationship to family history of schizophrenia to identify which factors appear to be related to the transmission of genetic risk.

Genetic antecedents of dopamine dysfunction in schizophrenia

BACKGROUND

Relatives of schizophrenic probands frequently manifest attenuated features of this illness including the negative symptoms and the milder positive psychotic symptoms. These two symptom dimensions are hypothesized to be associated with decreased and increased brain dopamine (DA) functions, respectively, raising the possibility that DA abnormalities may be present in the relatives of schizophrenic probands.

METHODS

Plasma homovanillic acid (HVA), the major DA metabolite and an indicator of brain DA activity, was measured in nonpsychotic, physically healthy first-degree relatives (n = 55) of schizophrenic probands and in normal subjects (n = 20) without a family history of schizophrenia.

RESULTS

Plasma HVA inversely correlated with negative symptoms and positively correlated with attenuated positive symptoms. Also, relatives had decreased plasma HVA compared to normal subjects, consistent with the fact that these relatives are characterized by negative symptoms. These findings were not related to major peripheral factors that could affect plasma HVA suggesting that the findings may reflect changes in brain DA activity.

CONCLUSIONS

Negative symptoms indicating a genetic diathesis to schizophrenia in relatives may have a biologic basis in reduced DA activity and the DA dysfunction of schizophrenia may have genetic antecedents. This opens an important new avenue for further study of DA in this illness.

Pretreatment plasma homovanillic acid in schizophrenia and schizoaffective disorder: the influence of demographic variables and the inpatient drug-free period

BACKGROUND

The relationship between plasma homovanillic acid (pHVA) and schizophrenic symptoms has not been conclusively determined. We reexamine pHVA levels in a new sample of patients with emphasis on demographic variables and the drug-free period.

METHODS

Plasma HVA levels were studied in 54 schizophrenic and schizoaffective-disordered, drug-free inpatients suffering from a psychotic exacerbation.

RESULTS

A significant correlation was observed between pHVA levels and the number of inpatient drug-free days in the total sample, as well as the schizophrenic patient subsample. Further, pHVA was significantly and positively correlated with the duration of illness in the schizophrenic patient subsample. Plasma HVA correlations with behavior, as measured by Brief Psychiatric Rating Scale factors (anxiety/depression and hostility/suspiciousness), emerged only when considering schizophrenic patients drug-free for more than 2 weeks. No correlation was found between pHVA and the age of illness onset or the duration of the delay of treatment of the first psychotic episode.

CONCLUSIONS

The effects of antipsychotic withdrawal on levels of pHVA in clinical populations may have to be examined and controlled for in future studies attempting to study the relationship between this metabolite and behavior in acutely ill, drug-free schizophrenic patients.

Effects of pimozide on the psychopathology of delusional disorder

1. The effects of pimozide on the psychopathology of delusional disorder were studied. 2. After six weeks, pimozide (2-12 mg/day) administration had no effect on the Brief Psychiatric Rating Scale, or in the psychological, social and occupational functioning, as measured by the Global Assessment of Functioning Scale. 3. When the different dimensions of the delusional experience were looked upon, no modifications were observed in any of them after six weeks of pimozide treatment. 4. These data failed to support the therapeutic role of pimozide in the treatment of delusional disorder and may suggest, when compared to other disorders with prominent delusions such as schizophrenia, a different neurobiology for the illness.

Pretreatment plasma HVA predicts neuroleptic response in manic psychosis

Elevated pretreatment plasma free homovanillic acid (HVA) predicted acute response to neuroleptic treatment in patients with manic psychosis. These findings suggest that plasma HVA may be a useful predictor of a successful short-term response in manic as well as schizophrenic psychoses, and that elevated pre-synaptic dopaminergic release may play a role in more than one group of psychotic disorders.

Association of plasma homovanillic acid with behavioral symptoms in patients diagnosed with dementia: a preliminary report

Neuroleptic treatment of psychotic symptoms or agitated behavior in elderly patients diagnosed with dementia is associated with reduced efficacy and increased rates of neuroleptic-induced parkinsonism in comparison to younger patients with schizophrenia. We report the first study to examine the relationship between an in vivo measure of dopaminergic function, plasma homovanillic acid (pHVA), and ratings of psychosis, agitation, and parkinsonism before and after neuroleptic treatment in dementia patients. Pretreatment pHVA was significantly correlated with parkinsonian rigidity, with a trend observed with agitation and hostility. Though mean pHVA did not change during perphenazine treatment, intraindividual change in pHVA at day 15 was correlated with improvement in hostility, with a similar trend for improvement in agitation. These preliminary findings are consistent with reports associating dopaminergic function with agitated, but not psychotic, symptoms in patients diagnosed with dementia, and with a reduced responsivity of dopaminergic systems to neuroleptic treatment in these patients.

Effects of antipsychotic medication on electromyographic responses to transcranial magnetic stimulation of the motor cortex in schizophrenia

OBJECTIVE

To assess the effect of antidopaminergic antipsychotic medication on the electromyographic (EMG) responses of thenar muscles to transcranial magnetic stimulation (TMS) of the motor cortex in schizophrenic patients.

METHODS

A group of nine drug naive schizophrenic patients was compared with a group of nine schizophrenic patients established on neuroleptic medication. Surface EMG recordings were made from the thenar muscles while patients maintained a weak isometric voluntary contraction. TMS was applied using a 9 cm circular stimulating coil centred over the vertex. The EMG responses to up to 50 magnetic stimuli were rectified and averaged.

RESULTS

There was no difference in threshold TMS strength for eliciting compound motor evoked potentials (cMEPs), or in their latency, in drug naive and medicated patients. In some patients the silent period (SP) was clearly made up of two parts and the percentage of control levels of voluntary EMG was measured in each component. During the early component of the SP there was a weaker (P<0.05) suppression of EMG in the medicated patients (mean 73.9 (SEM) 5.5% of control levels) compared with the drug naive patients (54.7 (SEM) 7.3% of control levels). This resulted in the latency of maximum suppression of voluntary EMG being longer (P<0.05) in the medicated patients (38.3 (2.4) ms) than in the drug naive patients (28.2 (0.7) ms). During the late component of the SP voluntary EMG was reduced to similar levels (P>0.05) in both medicated (48.2 (7.7)% of control levels) and drug naive (58 (7.8)% of control levels) patients.

CONCLUSION

The results are discussed with reference to the disrupted inhibition seen in the early part of the SP in Parkinson's disease and drug induced parkinsonism. The future uses of motor responses to TMS as a marker for the status of antipsychotic medication are considered.

New dopaminergic and non-dopaminergic theories in schizophrenia and their therapeutic impact

The dopamine (DA) hypothesis of schizophrenia, postulating that schizophrenia is characterized by increased dopamine function, has been the most influential theory on the pathogenesis of schizophrenia. It has recently been revised based on the appreciation that the core symptoms of schizophrenia may not be the positive (psychotic) symptoms, but rather the negative symptoms and the cognitive deficits found in schizophrenic patients. This revision has prompted the hypothesis that schizophrenia is characterized by both decreased prefrontal dopamine activity (causing deficit symptoms) and increased dopamine activity in mesolimbic dopamine neurons (causing positive symptoms). Notwithstanding this revision of a role for dopamine in schizophrenia, it has become increasingly evident that dysfunction of other monoaminergic systems may be as important in contributing to the pathophysiology of schizophrenia. Specifically, the putative role of serotonin (5-hydroxytryptamine, 5-HT) in schizophrenia is gaining considerable attention. Several observations, such as the ability of the 5-HT antagonist, ritanserin, to alleviate schizophrenic symptoms and, when added to haloperidol (Haldol®), to decrease its extrapyramidal side-effects (EPS), have stimulated studies into a role of 5-HT in schizophrenia. The finding that clozapine (Leponex®), clinically superior to conventional neuroleptics, is a weak DA2 antagonist but a potent 5-HT1c and 5-HT2 antagonist has further stimulated 5-HT-related research in schizophrenia.

Recent life stressors and biological markers in newly admitted psychotic patients

The association of recent life stressor severity to putative biological markers of stress was examined in 34 newly admitted patients with acute psychosis. Of the biological variables examined, only pretreatment admission serum cortisol was correlated with stressor severity. Pretreatment serum prolactin, plasma homovanillic acid (HVA), and methoxyhydroxyphen-ethylglycol were not associated with severity of recent life stressors. We controlled for clinical and psychosocial variables that might affect the relationship of stressor severity to biological markers, and found that duration of psychotic symptoms was negatively correlated with stressor severity; however, when both cortisol and duration were entered in a stepwise multiple regression analysis, only pretreatment admission cortisol remained significantly and positively correlated with stressor severity. These findings suggest that serum cortisol may be a useful biological marker when investigating the relationship of life stress to episode onset. In addition, pretreatment HVA was correlated with early neuroleptic response but not with stressor severity, suggesting that HVA has value as a predictor of response independent of recent life stressors.

First-episode neuroleptic-free schizophrenics: concentrations of monoamines and their metabolites in plasma and their correlations with clinical responses to haloperidol treatment

Thirty-two first-episode neuroleptic-free schizophrenics were treated with neuroleptics for 8 weeks. The monoamines and their metabolites, dopamine, norepinephrine, serotonin, homovanillic acid (HVA), 3-methoxy-4-hydroxy-phenylglycol(MHPG), and 5-hydroxyindoleacetic acid (5-HIAA) in plasma were measured to examine the association with treatment responses and psychopathology assessed according to the brief psychiatry rating scale (BPRS). No differences were noted in the pretreatment concentrations of monoamines and their metabolites between patients and healthy controls; however, during treatment the concentrations of HVA and MHPG were significantly reduced only in the schizophrenics who responded to treatment. Moreover, the HVA and MHPG reductions correlated significantly with improvements in BPRS scores. Since their plasma levels reflect to some extent central dopaminergic and noradrenergic activities, respectively, the present findings suggest the involvement of these systems in the pathogenesis of schizophrenia as well as the usefulness of such measurements as predictors of responsiveness to neuroleptics.

Prediction of short-term changes in symptom severity by baseline plasma homovanillic acid levels in schizophrenic patients receiving clozapine

The relationship between pretreatment levels of plasma homovanillic acid (pHVA) and the outcome of clozapine treatment was studied in 18 male patients with schizophrenia who were resistant to treatment with conventional neuroleptics. After 6 months of clozapine treatment, 7 patients demonstrated > or = 20% decrease in the Brief Psychiatric Rating Scale (BPRS) (responders), while 11 patients did not (non-responders). Responders and non-responders did not differ with respect to the baseline pHVA level. The BPRS Positive Symptom scores at 6 weeks and 3 months, but not those at baseline and 6 months, following initiation of clozapine treatment negatively correlated with pHVA levels for all patients. The correlations became stronger when only responders were included. No significant correlation between Positive Symptom scores and pHVA levels was observed for non-responders. The BPRS Total and Negative Symptom scores did not correlate with pHVA for all patients, responders or non-responders at any time. The percent decrease in the BPRS Positive Symptom scores from baseline at 6 weeks following clozapine treatment correlated significantly with pHVA levels in responders. These results suggest that pretreatment levels of pHVA can be used to predict relatively short-term changes in the positive symptoms of patients with schizophrenia receiving clozapine treatment, particularly for clozapine responders.

Sex differences in plasma homovanillic acid levels in schizophrenia and normal controls: relation to neuroleptic resistance

Plasma homovanillic acid (pHVA) levels were compared in a large number of neuroleptic-resistant and -responsive schizophrenic patients (male/female = 161/46) and normal controls (67/27), and correlated with various measures of psychopathology. Psychopathology was evaluated with the brief psychiatric rating scale, the Schedule for Affective Disorders and Schizophrenia-Change version (SADS-C) and SADS-C Global Assessment Scale, the Scale for Assessment of Negative Symptoms, the Scale for Assessment of Positive Symptoms (SAPS), and the Quality of Life Scale. No significant differences in pHVA levels between neuroleptic-resistant (n = 104) or -responsive (n = 103) schizophrenic patients, and normal controls, were found; however, there was a main effect for sex, due to higher pHVA levels in women than men. There were no diagnosis x gender or age effects on pHVA levels. No significant correlations were observed between psychopathology ratings and baseline pHVA levels, except with the Hallucinations subscale of SAPS in neuroleptic-responsive patients. Neither duration of neuroleptic washout nor plasma prolactin levels correlated with pHVA levels. Further studies on the origin and significance of the gender difference in pHVA are indicated.

Presynaptic dopaminergic function in the striatum of schizophrenic patients

The dopaminergic hypothesis of schizophrenia postulates increased brain dopaminergic activity. Two previous studies reported increased 18F-DOPA uptake with positron emission tomography in schizophrenic patients (n = 5, n = 7). In the present study, striatal dopaminergic function was assessed in vivo in six untreated schizophrenics and seven control subjects, comparable for age and sex. The 18F-fluoro-L-DOPA (18F-DOPA) uptake rate constant Ki was determined in the caudate and putamen using coregistered positron emission tomography and magnetic resonance imaging. No difference between groups for mean Ki was found. The variability of the 18F-DOPA uptake values was higher in the caudate (p < 0.01) and in the putamen (p < 0.001) in schizophrenic patients than in control subjects, suggesting that schizophrenia is a disorder involving heterogeneous states of the striatal presynaptic dopaminergic function.

A study of the potential confounding effects of diet, caffeine, nicotine and lorazepam on the stability of plasma and urinary homovanillic acid levels in patients with schizophrenia

Ten men inpatients who met DSM-III-R criteria for schizophrenia participated. On five occasions at least one week apart, each subject had an intravenous line placed at 0730 after an overnight fast. On each occasion blood samples were drawn at 0800 and hourly thereafter through 1200 noon for measurement of plasma homovanillic acid (HVA). Total four-hour urine collections were obtained for measurement of urinary HVA. Subjects received five experimental conditions, in randomized sequence: no intervention, smoking one cigarette per hour, drinking one caffeinated cola per hour, lorazepam 2 mg IV push, or a high monoamine meal. Baseline (0800) plasma HVA measures showed only minor intrinsic variability. The average standard deviation in baseline plasma HVA over five occasions of measurement was low relative to the changes in HVA produced during treatment with antipsychotic medications. The high monoamine meal significantly elevated plasma HVA, with a similar trend for urinary HVA. Neither caffeine, nicotine, nor lorazepam significantly affected plasma or urinary HVA.

Effect of benzodiazepines on plasma levels of homovanillic acid in anxious patients and control subjects

The effects of four logarithmically increasing doses of intravenous diazepam or placebo on plasma homovanillic acid (HVA) were determined in benzodiazepine-naive patients with panic disorder (PD) or generalized anxiety disorder (GAD), and in healthy controls. Plasma HVA was measured at baseline and 3 min after the first and fourth doses of diazepam/placebo. Mean baseline plasma HVA levels were significantly lower in PD patients compared with GAD patients and controls. Although plasma HVA levels decreased significantly with time in all groups, there was no diazepam effect. This study suggests that low dopaminergic activity may occur in a subset of anxious patients (PD), and that diazepam does not significantly affect dopaminergic activity as measured by plasma HVA in humans.

Improvement of schizophrenic symptoms and changes in plasma HVA concentrations, plasma anti-D2 and anti-5-HT2 receptor activities with clozapine

In order to investigate the biological mechanisms underlying the clinical efficacy of clozapine, 200 mg/day of clozapine was added to the drug regimens of 19 patients with chronic, anti-psychotic-resistant schizophrenia, and the plasma homovanillic acid (HVA), clozapine concentrations, anti-dopamine D2 and anti-serotonin 5-HT2 receptor activities were measured. After 28 days, six patients showed an improvement of more than 20% over baseline Brief Psychiatric Rating Scale (BPRS) scores. Mean plasma HVA concentrations and anti-D2 receptor activities did not change significantly in the entire group or in the six patients showing improvement. However, anti-5-HT2 receptor activities increased significantly in all 19 patients. Changes in BPRS scores did not correlate significantly with changes in plasma HVA or with changes in clozapine concentrations, or with anti-D2 and anti-5-HT2 receptor activities.

Lack of effect of laboratory-provoked anxiety on plasma homovanillic acid concentration in normal subjects

The present study was undertaken to investigate if acute anxiety can affect plasma concentrations of homovanillic acid (pHVA). Since elevated pHVA levels have been associated with severity of schizophrenic symptoms, the results of this study will help determine if the pHVA elevations are directly related to psychosis or if anxiety is also a contributory factor. Anxiety was provoked in 10 young normal subjects by a combined paradigm of mental arithmetic task and threat of electrical shock. A significant increase in self-ratings of anxiety, blood pressure, and plasma levels of norepinephrine, 3-methoxy-4-hydroxyphenylethyleneglycol and growth hormone indicated that the paradigm used was effective in provoking anxiety; however, anxiety did not affect pHVA concentrations. The results may support the notion that increased pHVA levels in severely ill schizophrenic patients are related to the schizophrenic pathophysiology rather than to anxiety.

Plasma homovanillic acid profile at different phases of the ovulatory cycle in healthy women

Variation in some central monoamine levels has been shown to be influenced by cyclical changes in gonadal hormones in women; however, there is less consensus about how the human menstrual cycle affects turnover of dopamine. Fluctuations in plasma homovanillic acid (HVA) are thought to represent changes in central dopamine turnover and activity and, some suggest, may be used to monitor the response to neuroleptic medication or to predict those more likely to respond to antipsychotic treatment. We have measured the effect of fluctuations in gonadal hormones on the level of plasma HVA at four consecutive points across the menstrual cycles of 30 healthy volunteers. We found no significant change in plasma HVA over the cycle and there was no correlation with either estradiol or progesterone levels. This study suggests that peripheral markers of central dopamine function do not change significantly with physiological changes in gonadal hormones levels.

Plasma homovanillic acid concentrations in catatonia

We investigated the dopamine metabolite plasma homovanillic acid (plasma HVA) levels in 37 catatonic patients on the day of admission before initial medication as well as in 17 healthy controls. In a prospective study catatonic syndrome was diagnosed according to criteria of Lohr and Wiesniwski (1987) and Rosebush et al (1990) whereas comorbid diagnosis was made by Diagnostic and Statistical Manual of Mental Disorders, 3rd ed, revised (DSM III/R) (APA 1987). On the day of admission blood samples were taken before initial medication. Compared to controls (80.1 +/- 40.1 pmol/mliter) catatonic patients showed significantly (P = 0.0286) increased plasma HVA (140.9 +/- 53.6 pmol/mliter). Catatonic patients free of neuroleptic medication (n = 21) differed significantly (p = 0.0416) from controls whereas neuroleptically treated catatonics (n = 16) did not. Our findings of increased plasma HVA in catatonia are explained by an alteration in either mesolimbic or mesocortical dopaminergic function, as is assumed in the case of schizophrenia. As an alternative, it may be due to increased nigrostriatal function, which can lead, as shown in animal experiments with the dopamine agonist amphetamine, to hypokinetic states resembling catatonia in humans.