Presynaptic receptors. Relevance to psychotropic drug action in man

Efficacy of clozapine in treatment-resistant psychosis and neuroleptic sensitivity: results of the Dutch open multi-center project

In an open multi-center study, 57 schizophrenic patients were treated with clozapine for indications of treatment-resistant psychosis or severe extrapyramidal side-effects caused by conventional neuroleptics. In 58% of the patients a clinical relevant improvement, expressed as percentage reduction of at least 50 from baseline BPRS scores was observed. With respect to extrapyramidal side-effects, a marked reduction was found upon treatment with clozapine. No major side-effects occurred, particularly agranulocytosis. It was concluded that clozapine is a potent antipsychotic agent that can be used safely when treatment is accompanied by frequent clinical and hematological monitoring.

The Effect of the Pain Symptom Cluster on Performance in Women Diagnosed with Advanced Breast Cancer: The Mediating Role of the Psychoneurological Symptom Cluster

BACKGROUND

Pain, depression, anxiety, sleep disturbances, and constipation were reported in different symptom clusters at different stages of breast cancer. Managing symptom clusters rather than individual symptoms can improve performance status.

AIM

The study examined the effect of pain symptom cluster (pain and constipation) on performance when mediated by the psychoneurological symptom cluster (depression, anxiety, and sleep disturbances) using age as a moderator.

DESIGN

A secondary analysis.

SETTINGS

Palliative care center at a tertiary medical center in northeast Ohio.

PARTICIPANTS

Eighty-six women diagnosed with advanced breast cancer.

METHOD

A quantitative cross-sectional approach.

RESULTS

Ordinal logistic regression showed that pain symptom cluster did not have a significant mediation effect on performance. Odds ratio indicated that subjects with pain symptom cluster were 63% more likely to be bedridden (odds ratio = 1.63, confidence interval = .69-3.84). Women who reported pain symptom cluster were 5% more likely to have psychoneurological symptom cluster (odds ratio = 1.05, confidence interval = .400-2.774). Stratified analysis of age showed no differences in performance. Post-hoc analysis showed that the components of pain symptom cluster had a significant effect on psychoneurological symptom cluster (odds ratio: 3 [1.18-7.62]).

CONCLUSIONS

Pain, constipation, depression, anxiety, and sleep disturbances were highly prevalent in women with advanced breast cancer. However, they tended to cluster in different symptom clusters. Although some findings were not significant, they all supported the direction of the tested hypotheses. Variations in symptom clusters research, including methodology, instruments, statistical tests, and chosen symptom cluster correlation coefficient, should be addressed.

Differently lasting effects of prenatal and postnatal chronic clozapine/haloperidol on activity and memory in mouse offspring

We evaluated the behavioral effects of chronic haloperidol (HAL) and clozapine (CLO) during gestation and CNS development, compared with transient treatments that stopped 1-3 weeks before the test.

RESULTS

1) Chronic HAL (6 mg/l in drinking water) but not HAL-withdrawal caused hypo-activity in open-field test on postnatal days (PNDs) 35, 42 and 56. However, hyper-activity was found in both CLO (90 mg/l) and CLO-withdrawal pups. 2) In the step-through test, retention performance was significantly higher in HAL-treated mice than in the controls on PND 42, as well as in withdrawal mice on PNDs 35 and 42. However, both chronic CLO (90 mg/l) exposure and CLO-withdrawal tended to improve the acquisition of memory. Furthermore, chronic CLO (180 mg/l) ameliorated scopolamine (3 mg/kg)-induced impairment of memory on PND 56. 3) In the water-maze test, both chronic HAL and HAL-withdrawal treatments significantly impaired performance on the 4th training day at PND 35, but not PNDs 42 and 56. Neither chronic CLO exposure nor CLO-withdrawal affected spatial memory. 4) Body weight following HAL/CLO administration decreased when compared with the controls during PND 21-35, but approached control levels at PND 40.

CONCLUSION

HAL doesn't elicit permanent behavioral changes in offspring. By contrast, CLO had longer-lasting effects than HAL. The pups at age before PND 35 seem more sensitive to HAL/CLO than elder pups.

On the trail of a cognitive enhancer for the treatment of schizophrenia

The aim of this critical review is to address that the study of cognition and antipsychotics is not always driven by logic and that research into real pro-cognitive drug treatments must be guided by a better understanding of the biochemical mechanisms underlying cognitive processes and deficits. Many studies have established that typical neuroleptic drugs do not improve cognitive impairment. Atypical antipsychotics improve cognition, but the pattern of improvement differs from drug to drug. Diminished cholinergic activity has been associated with memory impairments. Why atypical drugs improve aspects of cognition might lie in their ability to increase dopamine and acetylcholine in the prefrontal cortex. An optimum amount of dopamine activity in the prefrontal cortex is critical for cognitive functioning. Another mechanism is related to procedural learning, and would explain the quality of the practice during repeated evaluations with atypical antipsychotics due to a more balanced blockage of D2 receptors. Laboratory studies have shown that clozapine, ziprasidone, olanzapine, and risperidone all selectively increase acetylcholine release in the prefrontal cortex, whereas this is not true for haloperidol and thioridazine. A few studies have suggested that cholinomimetics or AChE inhibitors can improve memory functions not only in Alzheimer's disease but also in other pathologies. Some studies support the role of decreased cholinergic activity in the cognitive deficits while others demonstrate that decreased choline acetyltransferase activity is related to deterioration in cognitive performance in schizophrenia. Overall, results suggest the hypothesis that the cholinergic system is involved in the cognitive dysfunctions observed in schizophrenia and that increased cholinergic activity may improve these impairments. Furthermore, a dysfunction of glutamatergic neurotransmission could play a key role in cognitive deficits associated with schizophrenia. Further meta-analysis of various clinical trials in this field is required to account for matters on the grounds of evidence-based medicine.

Beyond specificity: effects of serotonin and serotonergic treatments on psychobiological dysfunction

Serotonin is a ubiquitous neurotransmitter with widespread projections that provide for the involvement of serotonin in the regulation of many biological and psychological functions. A variety of serotonin receptor subtypes exist that mediate overlapping psychobiological functions and that are targets for a new generation of medications. Although these new generation medications appear to possess great biochemical specificity, their actions extend to many psychiatric disorders, reflecting the many interactions of serotonergic subsystems.

Effects of 21 days treatment with fluoxetine on stimulated endogenous 5-hydroxytryptamine overflow in the rat dorsal raphe and suprachiasmatic nucleus studied using fast cyclic voltammetry in vitro

Changes in the extracellular concentration of 5-HT evoked by electrical stimulation of brain slices containing either dorsal raphe nucleus (DRN) or suprachiasmatic nucleus (SCN) from rats treated for 21 days with fluoxetine (5 mg/kg; i.p.) or water were monitored using fast cyclic voltammetry (FCV). Stimulated 5-HT overflow was enhanced significantly in both brain regions after 21 days treatment with fluoxetine but there was no change in the half time for re-uptake (t1/2). Concentration response curves for inhibition of electrically stimulated 5-HT overflow by 8-OH-DPAT (5-HT1a receptor agonist) or RU24969 (5-HT1b receptor agonist) in the DRN or SCN respectively were obtained in slices prepared from both groups of animals. There was a significant shift to the right in the dose-response curve for RU24969 in the SCN in fluoxetine treated animals but a shift to the left for the dose-response curve for 8-OH-DPAT in the DRN. These data suggest that down regulation of the 5-HT1b autoreceptors occurs in an axon terminal region (SCN) but that there is a sensitisation of 5-HT1a autoreceptor mechanisms controlling 5-HT overflow in the DRN.

Serotonin denervation enhances responsiveness of presynaptic dopamine efflux to acute clozapine in nucleus accumbens but not in caudate-putamen

Clozapine alters mesolimbic dopamine (DA) function but spares nigrostriatal DA function in laboratory animals, but the underlying mechanism is unknown. In the present study, acute intraperitoneal injection of clozapine (5-40 mg/kg) increased extracellular DA levels in nucleus accumbens (Acb) and caudate-putamen (CPu) of awake, freely moving rats as measured by in vivo brain microdialysis, without anatomic selectivity. However, in serotonin (5HT)-denervated rats acute clozapine preferentially enhanced DA levels in Acb as compared to CPu. Since (i) up-regulation of 5HT receptors on DA neurons may result from 5HT denervation, (ii) clozapine has potent anti-5HT action, and (iii) 5HT receptors are more dense in Acb than CPu, these data appear to add additional weight to previous suggestions that a serotonergic mechanism may partly underlie clozapine's mesolimbic selectivity.