Effect of adjuvant reserpine treatment on catecholamine metabolism in schizophrenic patients under long-term neuroleptic treatment

Psychiatric symptoms of noradrenergic dysfunction: a pathophysiological view

What psychiatric symptoms are caused by central noradrenergic dysfunction? The hypothesis considered in this review is that noradrenergic dysfunction causes the abnormalities in arousal level observed in functional psychoses. In this review, the psychiatric symptoms of noradrenergic dysfunction were inferred pathophysiologically from the neuroscience literature. This inference was examined based on the literature on the biology of psychiatric disorders and psychotropics. Additionally, hypotheses were generated as to the cause of the noradrenergic dysfunction. The central noradrenaline system, like the peripheral system, mediates the alarm reaction during stress. Overactivity of the system increases the arousal level and amplifies the emotional reaction to stress, which could manifest as a cluster of symptoms, such as insomnia, anxiety, irritability, emotional instability and exaggerated fear or aggressiveness (hyperarousal symptoms). Underactivity of the system lowers the arousal level and attenuates the alarm reaction, which could result in hypersomnia and insensitivity to stress (hypoarousal symptoms). Clinical data support the hypothesis that, in functional psychoses, the noradrenergic dysfunction is in fact associated with the arousal symptoms described above. The anti-noradrenergic action of anxiolytics and antipsychotics can explain their sedative effects on the hyperarousal symptoms of these disorders. The results of animal experiments suggest that excessive stress can be a cause of long-term noradrenergic dysfunction.

Management of treatment resistance in schizophrenia

A systematic approach to the evaluation and characterization of treatment resistance in schizophrenia has become increasingly important since the introduction of the second-generation antipsychotics. The need for accurate evaluation will increase further as other new antipsychotic medications are developed. Patients with schizophrenia may manifest poor response to therapy because of intolerance to medication, poor adherence, inappropriate dosing, as well as true resistance of their illness to antipsychotic drug therapy. Criteria for treatment-resistance are presented to help in standardizing treatment and clinical trials. As clinicians face the decision of when to change or augment antipsychotic medications, a clear understanding of the appropriate length of a treatment trial and which target symptoms respond to antipsychotic therapy is critical for maximizing response in patients with treatment-resistant schizophrenia.

Persistent psychosis after reduction in pre- and post-synaptic dopaminergic function

The purpose of this study was to evaluate the hypothesis that neuroleptic non-response in the face of "adequate" DA post-synaptic receptor blockade reflects failure of regulatory mechanisms to decrease DA pre-synaptic activity. Eight chronic schizophrenics, meeting rigorous criteria for neuroleptic non-response, were treated for four weeks with alpha-methylparatyrosine as an adjunct to their previously stable neuroleptic dose. Treatment with AMPT produced a prompt decrease in plasma HVA that was, on average, 72% lower at the end of the study. While there was also strong clinical evidence of reduction in central dopaminergic activity (both a significant reduction in dyskinetic movements and increase in extrapyramidal symptoms), there was virtually no change in severity of psychotic symptoms. Thus, in this group of non-responders, psychotic symptoms persisted despite both extensive dopamine post-synaptic receptor blockade and marked reduction of presynaptic activity. These symptoms may not be directly DA dependent.

Possible noradrenergic dysfunction in schizophrenia

In spite of extensive studies over the last 2 decades to find direct evidence in support of the dopamine hypothesis of schizophrenia, no undisputed experimental data has been obtained. In contrast, estimation of noradrenalin (another major catecholamine) and its metabolites in postmortem brain and in the cerebrospinal fluid appears to be producing consistent results. To understand the meaning of this change for the pathogenesis of the illness, we have carried out animal experiments in which reproducibility of schizophrenic signs and symptoms by noradrenergic dysfunction, and treatability of the disorder by modulation of noradrenergic activity were studied. First, psychophysiological signs in skin conductance responsiveness (nonhabituating or nonresponding change) and smooth pursuit eye movement (spiky or stepwise pursuit) could be reproduced by enhancing or suppressing central noradrenergic activity. Behavioral abnormalities resembling schizophrenic symptoms are known to be reproducible by over- or underactivity of the system (overarousal or underarousal syndrome). Secondly, the action of various drugs capable of modulating schizophrenic symptoms was analyzed in relation to noradrenergic activity. Haloperidol, in particular, had a potent suppressing effect on skin conductance activity (spontaneous fluctuation rate and habituation rate) when administered chronically, suggesting its inhibitory action on noradrenergic activity.