Drug-induced tardive dyskinesia

Dopamine D2 and angiotensin II type 1 receptors form functional heteromers in rat striatum

Identification of G protein-coupled receptors and their specific function in a given neuron becomes essential to better understand the variety of signal transduction mechanisms associated with neurotransmission. We hypothesized that angiotensin II type 1 (AT1) and dopamine D2 receptors form heteromers in the central nervous system, specifically in striatum. Using bioluminescence resonance energy transfer, a direct interaction was demonstrated in cells transfected with the cDNA for the human version of the receptors. Heteromerization did not affect cAMP signaling via D2 receptors but attenuated the coupling of AT1 receptors to Gq. A common feature of heteromers, namely cross-antagonism, i.e. the blockade of the signaling of one receptor by the blockade of the partner receptor, was tested in co-transfected cells. Candesartan, the selective AT1 receptor antagonist, was able to block D2-receptor mediated effects on cAMP levels, MAP kinase activation and β-arrestin recruitment. This effect of candesartan, which constitutes a property for the dopamine-angiotensin receptor heteromer, was similarly occurring in primary cultures of neurons and rat striatal slices. The expression of heteromers in striatum was confirmed by robust labeling using in situ proximity ligation assays. The results indicate that AT1 receptors are expressed in striatum and form heteromers with dopamine D2 receptors that enable drugs selective for the AT1 receptor to alter the functional response of D2 receptors.

Current topics in tardive dyskinesia in Japan

This article reviews current topics in tardive dyskinesia (TD), a movement disorder associated with the prolonged use of neuroleptic agents, especially therapeutic and preventive strategies which have been or are now being studied in Japan. Tardive dyskinesia has become a major problem in the clinical psychiatric field since the early 1970s in Japan, lagging behind Western countries by more than 10 years. The average prevalence rate of TD has been estimated as 7.7% in Japan, while it has been reported in the English literature at around 15 to 20%. Clinical trials of treatments for TD have been or are now being performed in Japan with a number of novel compounds, such as ceruletide, meclofenoxate, and rolipram; however, no effective treatment has yet been established and measures to prevent TD have therefore been emphasized. These include (i) the development of new antipsychotic drugs which are free from TD, (ii) the identification of risk factors from prospective longitudinal studies, and (iii) the investigation of genetic variations that could act as a marker to identify especially vulnerable patients within the whole population of patients who need neuroleptic therapy.

Tardive dyskinesia in elderly psychiatric patients in Singapore

The prevalence of tardive dyskinesia (TD) in 514 psychiatric patients who were 60 years and above in Singapore was found to be 27.6%. This is low compared with other studies done on elderly psychiatric patients in the West. Among the different ethnic groups, the Eurasians have the highest prevalence of 53.8% compared to the Chinese, Malays or Indians. Inpatients have a higher prevalence (31.5%) than outpatients (10.5%). Higher prevalence was also found in women, who were 2.2 times more common than men. 50% of the mentally retarded patients were found to have TD.

A prospective study of tardive dyskinesia in Japan

A large-scale, prospective study of tardive dyskinesia (TD) was performed in 11 psychiatric facilities in Japan. A total of 1595 psychiatric patients were enrolled in this study in 1987. The progress of these patients, with the exception of 490 dropouts, has now been followed up to 1988. The prevalence of TD at study entry was 7.6%, the annual incidence rate was 3.7% and the annual remission rate was 28.7%. Newly developed TD patients tended to be older, to have undergone more psychosurgery, and to have had lower neuroleptic doses than the patients who had not developed TD, whereas no specific variable could be detected as a factor associated with remission of TD. The results suggest that the incidence of TD is lower in Japan than that in Europe and North America.