Dopamine receptors. The D4 and schizophrenia

Treatment of behavioural disturbances in Parkinson's disease

Behavioural disorders in Parkinson's disease can grossly be subdivided in primary disturbances and those which are related to drug treatment. Depression and anxiety are a common feature in parkinsonian patients. Both occur independently of drug treatment. In general, most current antidepressive and anxiolytic drugs could be administered in Parkinson's disease with the same precautions as in the normal population. However, in single case reports modern serotonin reuptake blockers in Parkinson's disease have been accused to worsen parkinsonian motor condition. Combinations of serotonin reuptake inhibitors with MAO-inhibitors like selegiline should be used with caution. In the case of cognitive decline firstly an underlying depression should be disclosed or if existent be treated. Depression seems to be the single most important factor associated with the severity of dementia and early antidepressant treatment seems to decrease cognitive decline in depressed parkinsonian patients. Anticholinergic medications should be discontinued since they may cause mental side effects. Sleep disorders in Parkinson's disease are mainly caused by nocturnal akinesia, which causes sleep fragmentation or altered dreaming and nightmares, which might be a side-effect of dopaminergic treatment. In the first case the administration of a controlled release preparation of levodopa at bedtime may be indicated. If the sleep disorder is considered to be due to dopaminergic medication, a reduction of long-term acting agents like modern dopamine agonists and controlled-release levodopa should be considered. In severe psychotic states related to drug treatment antiparkinsonian therapy must be carefully analysed and, if possible, reduced. If motor condition worsens and/or psychiatric symptoms do not improve, initiation with "atypical" neuroleptics like clozapine is indicated. The pharmacological and clinical properties of new antipsychotic drugs that can be used in Parkinson's disease are revised.

The relative abundance of dopamine D4 receptor mRNA in post mortem brains of schizophrenics and controls

An increase in dopamine D4 receptors has recently been reported in post mortem brain samples from schizophrenics. We have attempted to complement this finding by assessing the levels of the specific messenger RNA (mRNA) for the D4 receptor, using the technique of quantitative RNA-PCR. No significant differences in the levels of expression of mRNA for the D4 receptor were found in the brains from schizophrenics compared to controls. The relationship between D4 receptors and schizophrenia, therefore, remains unclear.

Psychiatric genetics: research challenges and pathways forward

Lessons from past psychiatric genetic research, together with key issues in psychiatry requiring genetic investigation, are reviewed in order to consider the implications for the ways forward. It is argued that traditional quantitative genetics needs to use a combination of twin, adoptee, and family strategies, to examine continuities and discontinuities in psychopathology between childhood and adult life, to compare dimensions and categories, to employ adequate conceptualization and measurement of disorders, to use statistical techniques based on latent constructs, to use biological trait indicators where possible, to examine risk factors as well as diseases, to include good measures of postulated environmental risk variables, to study the interplay between genes and environment, and to study the key assumptions underlying genetic strategies. Molecular cytogenetics needs to consider both the general and specific psychopathological risks associated with chromosome abnormalities and to examine the mechanism involved, to examine the role of submicroscopic chromosomal deletions and of mitochondrial disorders, and to investigate the mechanisms involved in trinucleotide repeat amplifications that take place during intergenerational transmission. Molecular genetics needs to make greater use of smaller pedigrees in view of the concerns over phenotypic definition and genetic heterogeneity in very large extended dense pedigrees, to use sib-pair designs in view of the likelihood that most psychiatric disorder will prove to be multifactorial, to combine association strategies with linkage analyses, to pay careful attention to the definition of phenotypes in probands, to remain in close touch with other branches of biological psychiatry, and to make effective use of collaboration between centers. To date, transgenic models have had a rather limited application in psychiatry but, despite their difficulties, they are likely to provide an underpinning for gene therapy in disorders where that seems feasible.