Age-related reduction in dopamine D1 receptors in the human brain: from late childhood to adulthood, a positron emission tomography study.

Age-dependent decrease in dopamine receptor density throughout adulthood is well described, meanwhile less is known about development of dopamine system in humans and in vivo it has not been investigated. We examined dopamine D1 receptor (D1DR) binding in the cerebral cortex and striatum of 12 adolescents (mean age 13.5+/-1.8 years) and 18 young adults (25+/-2.3 years) using positron emission tomography (PET) and radioligand [(11)C]SCH23390. Over the age span of 10-30 years [(11)C]SCH23390 binding (binding potential, BP) declined in all brain regions. The rate of BP decline was age-segment and brain region dependent. Most pronounced decline in BP was observed in the cortical regions during adolescence (mean BP in adults lower by 14-26% as compared to adolescents, P<0.0001). Significantly slower rate of decline in BP was observed in two cortical regions (orbitofrontal and posterior cingulate cortices) and striatal regions. The present PET-study provides new evidence on the development of D1DR in humans in vivo which is of critical importance for understanding of the biology of neurodevelopmental disorders.

Reduced dopamine transporter binding in patients with juvenile myoclonic epilepsy.

BACKGROUND: Behavioral and cognitive problems are frequently encountered in juvenile myoclonic epilepsy (JME). The underlying mechanisms are unknown. Based on previous data showing that the dopamine system is involved in motor as well as cognitive functions, we tested whether JME may be associated with changes in this system, and if such changes are linked to interictal dysfunctions in these patients. METHOD: PET and [(11)C]PE2I was used to investigate the regional binding potential to the dopamine transporter (DAT) in 12 patients with JME and 12 healthy controls. Binding potential was calculated in the midbrain, substantia nigra, caudate, and putamen. We also tested possible correlations between the respective measures and performance in several neuropsychological tests. RESULTS: Patients had a reduced binding potential in the substantia nigra and midbrain (p = 0.009 and 0.007), and normal values in the caudate and putamen. They also exhibited impaired psychomotor speed and motor function, which in some tests correlated with DAT binding potential in the midbrain. CONCLUSION: Dopamine signaling seems impaired in the target regions for dopaminergic neurons (the striatum and frontal lobe), and related to several interictal dysfunctions in JME. The findings add a new aspect to the pathophysiology of JME.

Shared memory representations for programming of lifting movements and associated whole body postural adjustments in humans.

This study examined whether the same memory representation is used for the parametric control of precision lifting and associated postural adjustments (APAs). Fifteen adults lifted object of different weights between the thumb and index finger. The employed grip, load (vertical lifting) forces, and ground reaction forces were recorded and the centre of pressure (COP) displacement as well as the corresponding first time derivatives were calculated. A highly significant correlation was found between the maximum rates of the load force, grip force and COP displacement rate. Different loads also influenced the onset of the COP displacement. The results corroborate the idea that the same memory representations which are used to control the manipulative lifting movement also control the APAs.

Investigations of pneumocystosis among humans and rodents in Lithuania.

Pneumocystosis (Pneumocystis carinii pneumonia) is a parasitic disease which in Lithuania used to be diagnosed only with the use of pathohistological methods. The aim of our study was to determine prevalence of P. carinii antibodies among children and women, using immunochemical method (ELISA) and to find out which groups of patients have higher antibody titres. We also addressed the question of infection with P. carinii among rodents. After investigating 9 species of rodents it was found that mostly infected is brown rat (Rattus norvegicus)--42.9% of them were found infected. The least infected was bank vole (Clethrionomys glareolus)--5.9%. The brown rat lives on hatch of domestic birds, rabbits or drinks eggs, while rodents in nature live on insects, molluscs, amphibians etc. European water voles (Arvicola terrestris) and field voles (Microtus arvalis) are vegetable feeders. Our data shows that those species of rodents were not infected with pneumocysts.