Bromocriptine for "negative" schizophrenia

Bromocriptine improves digit symbol substitution test scores in neuroleptic-treated chronic schizophrenic patients

The cognitive effects of bromocriptine (10 mg/day) in chronic neuroleptic-treated schizophrenic patients were studied in a 4-month trial. Ten neuropsychological variables were used for the evaluations. Nine patients and seven controls completed the study. They were tested three times: before the beginning of the study, and after 2 and 4 months of treatment. The results showed that treated patients globally performed significantly better than the controls (P < 0.05), and that the digit symbol substitution test was significantly improved (P < 0.03). The WAIS performance score was also significantly improved (P < 0.02). The picture arrangement test was improved, but did not reach significance (P < 0.07). Verbal tests were not improved. It therefore appears that addition of a D2 dopamine agonist in neuroleptic-treated patients can improve some of their cognitive functions. Two explanations can be proposed: i) bromocriptine decreases neuroleptic-induced motor side effects or ii) has an effect on a putative hypodopaminergic function in schizophrenia.

The D2-family receptor agonist bromocriptine but, not nicotine, reverses NMDA receptor antagonist-induced working memory deficits in the radial arm maze in mice

Hypofunction of the NMDA receptor (NMDAr) may underlie cognitive deficits associated with schizophrenia and other psychiatric conditions including working memory (WM) impairments. Given that these deficits link closely to functional outcome, treatments remediating such deficits require identification. NMDAr hypofunction can be modeled via treatment with the antagonist MK-801. Hence, the present study determined whether cholinergic or dopaminergic agonists attenuate MK-801-induced WM deficits in mice. WM was assessed in male C57BL/6 mice trained on an automated 12-arm radial arm maze (RAM) paradigm, wherein rewards were delivered after the first but, not after subsequent entries into WM arms (8/12) and never delivered for entries into reference memory (RM) arms (4/12). Mice were then treated with MK-801 (vehicle or 0.3 mg/kg) and nicotine (vehicle, 0.03 or 0.30 mg/kg) in a cross-over design. After a 2-week washout, mice were then retested with MK-801 and the dopamine D₂-family receptor agonist bromocriptine (vehicle, 3 or 10 mg/kg). In both experiments, MK-801 reduced WM span and increased RM and WM error rates. Nicotine did not attenuate these deficits. In contrast, a bromocriptine/MK-801 interaction was observed on WM error rate, where bromocriptine attenuated MK-801 induced deficits without affecting MK-801-induced RM errors. Additionally, bromocriptine produced the main effect of slowing latency to collect rewards. Hence, while NMDAr hypofunction-induced deficits in WM was unaffected by nicotine, it was remediated by treatment with the dopamine D₂-family agonist bromocriptine. Future studies should determine whether selective activation of dopamine D₂, D₃, or D₄ receptors remediate this NMDAr hypofunction-induced WM deficit.

The Obesity-Impulsivity Axis: Potential Metabolic Interventions in Chronic Psychiatric Patients

Pathological impulsivity is encountered in a broad range of psychiatric conditions and is thought to be a risk factor for aggression directed against oneself or others. Recently, a strong association was found between impulsivity and obesity which may explain the high prevalence of metabolic disorders in individuals with mental illness even in the absence of exposure to psychotropic drugs. As the overlapping neurobiology of impulsivity and obesity is being unraveled, the question asked louder and louder is whether they should be treated concomitantly. The treatment of obesity and metabolic dysregulations in chronic psychiatric patients is currently underutilized and often initiated late, making correction more difficult to achieve. Addressing obesity and metabolic dysfunction in a preventive manner may not only lower morbidity and mortality but also the excessive impulsivity, decreasing the risk for aggression. In this review, we take a look beyond psychopharmacological interventions and discuss dietary and physical therapy approaches.

Bromocriptine mitigated paliperidone metabolic and neuro-hormonal side effects and improved negative domain in a case of early onset schizophrenia

We report a case of early onset schizophrenia that responded favourably to paliperidone but experienced hyperprolactinaemia, tremors, and weight gain, with impaired fasting glycaemia. Addition of bromocriptine helped with both hyperprolactinaemia and tremors, but also brought about euglycaemia and, strikingly, ameliorated negative symptoms.

Neural substrates underlying effort computation in schizophrenia

The lack of initiative, drive or effort in patients with schizophrenia is linked to marked functional impairments. However, our assessment of effort and motivation is crude, relying on clinical rating scales based largely on patient recall. In order to better understand the neurobiology of effort in schizophrenia, we need more rigorous measurements of this construct. In the behavioural neuroscience literature, decades of work has been carried out developing various paradigms to examine the neural underpinnings of an animal's willingness to expend effort for a reward. Here, we shall review this literature on the nature of paradigms used in rodents to assess effort, as well as those used in humans. Next, the neurobiology of these effort-based decisions will be discussed. We shall then review what is known about effort in schizophrenia, and what might be inferred from experiments done in other human populations. Lastly, we shall discuss future directions of research that may assist in shedding light on the neurobiology of effort cost computations in schizophrenia.

Dopaminergic modulation of semantic priming in healthy volunteers

BACKGROUND

Semantic priming is a function related to prefrontal cortical (PFC) networks and is lateralized. There is evidence that semantic priming underlies dopaminergic modulation. It is known that the D1-receptor is more abundant in prefrontal networks; however, until now there have been no studies investigating the selective modulation of semantic priming with dopamine agonists. Furthermore, D1 receptor dysfunction has been described in schizophrenia, and patients with formal thought disorder seem to have disturbed focusing of associations and increased indirect priming.

METHODS

With a subtraction design, we compared the influence of pergolide (D1/D2 agonist) with bromocriptine (D2 agonist) and placebo, in a randomized, double-blind, crossover design in 40 healthy male volunteers. Subjects performed a lateralized lexical decision task including direct and indirect related prime-target pairs (stimulus onset asynchrony = 750 msec).

RESULTS

Only on pergolide a decrease of the indirect priming in the left hemisphere presentations was found.

CONCLUSIONS

These findings point to a potential selective modulation of agonists with a D1 component on the focusing of semantic associations. The clinical relevance of this study is that it might help the development of therapeutic strategies for treating cognitive deficits in schizophrenia and Parkinson's disease, which are highly relevant to the functional outcome.

Differential dopaminergic modulation of executive control in healthy subjects

RATIONALE

Executive control (EC) has different subcomponents, e.g., response inhibition (measured, for example, by the Stroop task) and working memory (WM-measured, for example, by delayed response tasks, DRT). EC has been associated with networks involving the prefrontal cortex (PFC). Moreover, there is evidence that dopamine agonists, especially those with a D1 profile, may modulate EC, since in the PFC D1 subtype receptors are more abundant.

OBJECTIVE

This study aimed to selectively distinguish whether D1 versus D2 dopamine agonism differentially influences EC related to the inhibition of irrelevant information and WM. Because of its D1 component, we predicted that the administration of pergolide (mixed D1/D2 agonist), in comparison with bromocriptine (D2 selective agonist) and placebo, would enhance performance in both EC tasks. Using a lateralized Stroop task, we predicted a decrease in the interference effect, as well as error rates, while no increase in facilitation effects. For the DRT task, we predicted fewer error scores in the delay condition.

METHODS

Forty male healthy subjects participated in this randomized, double-blind, placebo-controlled, crossover study.

RESULTS

For the Stroop task no superiority of pergolide was found; however, with bromocriptine, decreased interference was found. No modulation of lateralization effects was shown in interference measures. Moreover, subjects on pergolide showed an absence of facilitation effects. No effects of either agonist were found for the DRT.

CONCLUSION

Our findings suggest that dopamine agonists modulate two EC tasks differently. Furthermore, there seems to be a selective modulation of different aspects of the Stroop task.

Aboulia: neurobehavioural dysfunction of dopaminergic system?

Recent advances in the understanding of the neural substrates of goal-directed behaviour have created new interest in unlocking the mystery behind those disorders that are characterized by poverty of thought and action. In this review, various studies will be considered which proffer converging evidence that the dopaminergic brain circuitry running from ventral tegmental areas in the midbrain, via nucleus accumbens in the forebrain, to the frontal cortex, tends to produce aboulia when its restitutive function fails. Such aboulic deficits occur in various neurological and psychiatric disorders in which they have profound implications for the patients' management, rehabilitation and social interactions. We begin by examining the consequences of dopamine agonism and antagonism in pre-clinical studies and draw on the inferences that can be made from studies in humans. We then go on to discuss aboulic features in neuropsychiatric conditions, focusing on clinical manifestation, animal models, abnormal dopamine activity and pharmacological interventions.

Body weight gain induced by antipsychotic drugs: mechanisms and management

Long-term administration of typical and atypical antipsychotic drugs (AP) induces excessive weight gain which afflicts up to 50% of patients, impairs health and interferes with treatment compliance. Basic and clinical research has shown that AP may affect body weight through diverse mechanisms. Increased appetite is probably related to the interaction of AP with neuronal receptors to dopamine, serotonin and histamine. Additional metabolic-endocrine disruption of weight regulation may be related to the effects of AP-induced hyperprolactinaemia on gonadal-adrenal steroids and insulin sensitivity. In humans, programmed physical activity, dietary restriction, anorectic agents, and drugs that counteract hyperprolactinaemia have been shown to be successful in a limited number of studies. Two novel strategies could expand the available therapeutic options. First, in preclinical experiments in female rats the estradiol antagonist/agonist drug tamoxifen or estradiol itself have been shown to completely prevent the obesity provoked by the AP sulpiride, and to induce an endocrine-metabolic milieu that seems to counteract AP-induced obesity. Secondly, it has also been shown that oral antihyperglycaemic agents such as metformin may decrease body weight and counteract insulin resistance and hyperinsulinaemia which is correlated with several metabolic abnormalities in obese subjects. Lastly, estradiol replacement, tamoxifen and/or antihyperglycaemic agents are not devoid of significant side-effects, and these drugs have not been tested in obese psychiatric patients. Therefore, further research is needed before their clinical use may be recommended.

Treatment of negative symptoms in schizophrenia and schizoaffective disorder by selegiline augmentation of antipsychotic medication. A pilot study examining the role of dopamine

It has been suggested that schizophrenic negative symptoms may be manifestations of regionally deficient CNS dopaminergic activity. We sought to test this hypothesis by openly treating patients on chronic antipsychotic medication who showed prominent negative symptoms with low-dose selegiline (5 mg b.i.d.), a monoamine oxidase-B inhibitor that selectively enhances dopaminergic activity. Twenty-one patients meeting DSM-III-R criteria for chronic schizophrenia (N = 14) or schizoaffective disorder (N = 7) with prominent negative symptoms were studied. Subjects had been kept at their current antipsychotic and antiparkinsonian medication dose levels for at least a month before the study, which was continued unchanged throughout the trial. Over 6 weeks of selegiline treatment, a 34.7% reduction in negative symptoms was demonstrated on the Scale for the Assessment of Negative Symptoms. There were also reductions in depressive symptoms (21-item Hamilton Depression Scale dropped 36.8%) and extrapyramidal symptoms (Simpson-Angus Extrapyramidal Symptom Scale scores dropped 27.7%), but no change was observed in the severity of positive symptoms as measured by the Brief Psychiatric Rating Scale. Global clinical improvement was demonstrated, with mean Clinical Global Impressions Scale score rising 17.6%. These findings support the hypothesis that negative symptoms, as well as extrapyramidal symptoms and certain depressive symptoms, may be manifestations of regionally deficient dopaminergic activity.

Motivational deficits after brain injury: effects of bromocriptine in 11 patients

OBJECTIVE

To test the hypothesis that treatment with bromocriptine would ameliorate deficits in clinical motivation, responsiveness to reward, and frontal cognitive function after brain injury.

METHOD

An open trial in six men and five women who had had either traumatic brain injury or subarachnoid haemorrhage between two months and five years previously. After repeated baseline assessments, bromocriptine was given in gradually increasing doses. Assessments were repeated at increasing doses, during maintenance, and after withdrawal. Novel structured instruments for quantifying motivation were developed; measures of anxiety and depression, and cognitive tests sensitive to motivation or frontal lobe involvement were also given.

RESULTS

Bromocriptine treatment was followed by improved scores on all measures other than mood. Improvement was maintained after bromocriptine withdrawal in eight of the patients.

CONCLUSION

Poor motivation in patients with brain injury may result from dysfunction in the mesolimbic/mesocortical dopaminergic circuitry, giving rise to associated deficiencies in reward responsiveness and frontal cognitive function.

New pharmacotherapeutic modalities for negative symptoms in psychosis

Negative symptoms in schizophrenia comprise a psychopathologic and pathophysiologic syndrome which is absent from normal mental function. Renewed interest in negative symptoms has led to the development of better measuring instruments, among which is the Positive And Negative Syndrome Scale (PANSS), which provides a way of measuring and reporting positive and negative symptoms in a balanced and convenient form. A number of strategies are being investigated for treating negative symptoms. Dopamine agonists such as levodopa, amphetamines and bromocriptine have been shown to produce improvements in negative symptoms, although good, well-controlled clinical trials are lacking. Partial dopamine agonists, such as MAR 327, are also currently under investigation and results are expected soon. Tricyclic, selective serotonin reuptake inhibitors and monoamine oxidase antidepressants appear to be able to modify negative symptoms in schizophrenia, although, once again, carefully designed trials are needed. Modification of GABAergic transmission has shown little promise, but the use of glycine to augment transmission at N-methyl-D-aspartate (NMDA) synapses suggests that the strategy may be beneficial. These results also imply that altered glutamate receptor function may be partly responsible for negative symptoms. One strategy that has been shown to have a beneficial effect against negative symptoms is combined serotonin/dopamine antagonism. Clozapine was found to have this profile after its introduction, and the recently introduced antipsychotic, risperidone was developed intentionally to be a combined 5-HT2/D2 antagonist. Both risperidone and clozapine have been shown to be effective against negative symptoms. One problem associated with the assessment of drug effects on negative symptoms, however, is that drugs can act on both primary and secondary negative symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)

The therapeutic potential of bromocriptine in neuropsychological rehabilitation of patients with acquired brain damage

1. Activation of neuropsychological rehabilitation by pharmacological agents is a promising therapeutic strategy. 2. Reports of single cases and case series claim improvement of akinetic mutism, non-fluent aphasia, apathy, attentional and other neuropsychiatric disturbances after treatment with bromocriptine, a D2 dopamine receptor agonist. 3. A critical review of published reports and own experiences discusses the results in the light of pharmacological and neurobiological considerations. 4. Dopaminergic stimulation after certain kinds of brain damage might influence neuronal recovery and/or substitute dopaminergical linked functions after destruction of the corresponding neurons. 5. Although controlled clinical studies are very difficult to design and such evidence is still lacking, preliminary recommendations are given with regard to differential indications, drug regime and evaluation criteria.

[Positive and negative symptoms in schizophrenia: a current overview]

The purpose of this article is to summarize the results of studies examining the validity of the positive and negative sub-types of schizophrenia as proposed by Crow. The authors summarized Crow's model's predictions in the form of 12 research questions and examined whether its predictions were confirmed. The following predictions are generally confirmed by the data collected: (i) it is possible to measure negative symptoms with accuracy; (ii) the negative symptoms predict a deterioration; (iii) the negative symptoms are generally correlated with overall cognitive deficits; (iv) each dimension appears to have distinct neurobiological substrata. However, several elements of the Crow model are not supported by the data collected. Among the necessary modifications, the most important are as follows: (i) it appears more productive to conceive of the negative symptoms as distinct dimensions, rather than distinct diseases; (ii) at least three dimensions exist for describing the symptoms of schizophrenia; (iii) the negative symptoms are not necessarily intrinsic to the schizophrenic process, and they may be due to other causes; (iv) the negative symptoms are not necessarily irreversible, and can be improved under ataractics; (v) the positive symptoms, in particular those relating to disorganization, can also be correlated with cognitive deficits.

Psychopharmacologic treatment of negative schizophrenic symptoms

Diverse pharmacologic agents have been reported to be effective in treating negative schizophrenic symptoms (NSS). In light of this large and growing literature, as well as of reconceptualizations of the underlying pathophysiology of NSS, the time may have come to reject models that assume "irreversibility" of NSS. However, flaws in existing studies prevent closure regarding the reversibility of, and by inference the treatability of, NSS. Guidelines for future studies are articulated, e.g., the need to distinguish primary from secondary NSS, to include drug-free subjects with a predominance of NSS in clinical trials, and to use well-validated and psychometrically sound instruments for assessing NSS.

A comprehensive macrophage-T-lymphocyte theory of schizophrenia

Chronic macrophage activation with subsequent failure of activated macrophages to properly control T-lymphocyte secretion of interleukin-2 and interleukin-2 receptors is proposed as the basic biological mechanism of schizophrenia. Fundamental to this theory are the clinical observations on interleukin-2 provoking the active phase symptoms of schizophrenia in psychiatrically normal human volunteers and macrophage cytokines producing the prodromal and residual phase symptoms. This theory provides a completely new and unified mechanisms for the antipsychotic action of typical and atypical neuroleptics, bromocriptine, naloxone and DMSO. Furthermore, this hypothesis reveals why the dopamine theory of schizophrenia was a false lead. The effects of prolactin, estrogens and androgens are consistent with the model. Age of onset, male/female incidence, course of the disease from prodromal to active to residual phase, the protection afforded by rheumatoid arthritis and the close relationship between depression and schizophrenia can be explained by this theory. The gastrointestinal tract is suggested as the preferred site to investigate for the cause of the immune activation in schizophrenia.

The psychopathology, neuropsychology, and neurobiology of associative and working memory in schizophrenia

A large number of psycholinguistic findings on how human beings store lexical information suggest the existence of associative memory, which may be characterized by a large capacity and a long duration. Its anatomical basis supposedly is, at least in part, the frontal lobes, and some of its functional characteristics have been tentatively linked to dopamine release. Working memory has a limited capacity, lasts only for seconds and is relevant for goal-directed behavior. Its anatomical basis in the frontal cortex is established and strong evidence suggests the involvement of dopaminergic pathways. Experimental evidence using several lexical decision tasks and a delayed response task is provided to demonstrate that some characteristic features of schizophrenic thinking--in particular the rapid shift of associations, the indirect relationship of associations, the overly abstract or overly concrete use of concepts, the lack of context-sensitivity and of general integrative function and intellectual capacity--can be explained in terms of an activation or disinhibition of associative memory, and of a dysfunctional working memory. The findings serve as an example of schizophrenia research in a cognitive neuroscience framework.

Akinesia: a syndrome common to parkinsonism, retarded depression, and negative symptoms of schizophrenia

A distinct hypokinetic syndrome appears to exist across several different neuropsychiatric diagnoses, involving (1) slowed motor activity with difficulty initiating and sustaining behaviors, (2) anhedonia with depressed mood and reduced affective range, and (3) cognitive impairment. Specifically, three well-recognized states--parkinsonism, retarded depression, and the negative symptoms of schizophrenia--prominently feature the components of this syndrome, and reduced dopamine turnover in the brain has been hypothesized to play a part in the pathophysiology of each. While aspects of this conceptualization remain controversial, it generates testable hypotheses that could have implications for the understanding and treatment of these states.