Longitudinal physical activity trajectories from childhood to adulthood and their determinants: The Young Finns Study.

Determining lifelong physical activity (PA) trajectories and their determinants is essential to promote a physically active lifestyle throughout the life-course. We aimed to identify PA trajectories from childhood to midlife and their determinants in a longitudinal population-based cohort. This study is a part of the Cardiovascular Risk in Young Finns Study. From 1980, a population-based cohort (N = 3596; 1764 boys/1832 girls, age 3-18 years) has been followed up for 31 years. PA indices were formed based on self-reported data (between age 9-49 years) on frequency, duration, and intensity of leisure (during childhood) or high-intensity (at later age) PA and on sports club participation/competitions. PA trajectories were analyzed using group-based trajectory modeling. Childhood (age 12 years), young adulthood (age 24 years), and early midlife (age 37 years) determinants were analyzed. Five PA trajectories were identified: persistently active (6.6%), decreasingly active (13.9%), increasingly active (13.5%), persistently low active (51.4%, reference group), persistently inactive (14.6%). In childhood, rural residential area (OR 0.45, 95% CI 0.21-0.96) and high academic performance (OR 2.18; 95% CI 1.58-3.00) associated with persistently active group. In early midlife, smoking (OR 1.66; 95% CI 1.07-2.58) associated with persistently inactive group, regular alcohol drinking (OR 2.91; 95% CI 1.12-7.55) with persistently active group and having children (OR 2.07; 95% CI 1.27-3.38) with decreasingly active group. High adulthood education associated with both decreasingly (OR 1.87; 95% CI 1.05-3.35) and increasingly (OR 2.09; 95% CI 1.19-3.68) active groups. We identified five PA trajectories from childhood into midlife. Most prominent determinants were academic achievement, education, having children and health habits (i.e. smoking/alcohol use).

Reduced aggression in AMPA-type glutamate receptor GluR-A subunit-deficient mice.

The importance of AMPA-type glutamate receptors has been demonstrated in neuronal plasticity and in adaptation to drugs of abuse. We studied the involvement of AMPA receptors in social interaction and anxiety and found that in several paradigms of agonistic behavior naïve male mice deficient for the GluR-A subunit- containing AMPA receptors are less aggressive than wild-type littermates. GluR-A deficient mice and wild-type littermates exhibited similar basic behavior and reflexes as monitored by observational Irwin's test, but they tended to be less anxious in elevated plus-maze and light-dark tests. Maternal aggression or male-female encounters were not affected which suggests that male hormones are involved in the expression of suppressed aggressiveness. However, testosterone levels and brain monoamines can be excluded and found to be similar between GluR-A deficient and wild-type littermates. The reduced AMPA receptor levels caused by the lack of the GluR-A subunit, and measured by a 30% reduction in hippocampal [3H]-S-AMPA binding, seem to be the reason for suppressed male aggressiveness. When we analyzed mice with reduced number of functional AMPA receptors mediated by the genomic introduced GluR-A(Q582R) channel mutation, we observed again male-specific suppressed aggression, providing additional evidence for GluR-A subunit-containing AMPA receptor involvement in aggression.

The effects of quinine and 4-aminopyridine on conditioned place preference and changes in motor activity induced by morphine in rats.

1. The effects of two unselective potassium (K(+)-) channel blockers, quinine (12.5, 25 and 50 mg/kg) and 4-aminopyridine (1 and 2 mg/kg), on conditioned place preference and biphasic changes in motor activity induced by morphine (10 mg/kg) were tested in Wistar rats. Quinine is known to block voltage-, calcium- and ATP-sensitive K(+)-channels while 4-aminopyridine is known to block voltage-sensitive K(+)-channels. 2. In the counterbalanced method, quinine attenuated morphine-induced place preference, whereas 4-aminopyridine was ineffective. In the motor activity test measured with an Animex-activity meter neither of the K(+)-channel blockers affected morphine-induced hypoactivity, but both K(+)-channel blockers prevented morphine-induced secondary hyperactivity. 3. These results suggest the involvement of quinine-sensitive but not 4-aminopyridine-sensitive K(+)-channels in morphine reward. It is also suggested that the blockade of K(+)-channels sensitive to these blockers is not sufficient to prevent morphine-induced hypoactivity whereas morphine-induced hyperactivity seems to be connected to both quinine- and 4-aminopyridine-sensitive K(+)-channels.

The effects of diazepam and zolpidem on cocaine- and amphetamine-induced place preference.

Drugs such as benzodiazepines, which enhance the effects of inhibitory neurotransmitter gamma-amino butyric acid (GABA), are known to modulate the mesocorticolimbic dopaminergic system, which is considered to mediate the rewarding effects of psychostimulants. The effects of diazepam, a benzodiazepine that binds unspecifically to omega 1- (omega1-) and omega2-receptors, and zolpidem, a nonbenzodiazepine drug that binds preferentially to omega1-receptors, on cocaine- and amphetamine-induced place preference were evaluated in Wistar rats. In tests using the counterbalanced method, neither diazepam (0.2, 1, and 5 mg/kg) nor zolpidem (2.5, 5, and 10 mg/kg) alone induced place preference or place aversion. Diazepam pretreatment prevented both cocaine- and amphetamine-induced (15 and 9 mg/kg, respectively) place preference; however, at doses that were earlier shown to cause sedation and amnesia, zolpidem failed to prevent either cocaine- or amphetamine-induced place preference. These results suggest that diazepam interferes with the rewarding properties of the psychostimulants, whereas zolpidem is less effective in this respect, possibly due to differential distribution of omega1- and omega2-receptors in the brain.

The acute effects of amphetamine derivatives on extracellular serotonin and dopamine levels in rat nucleus accumbens.

The acute effects of amphetamine derivatives on extracellular concentration of serotonin (5-HT) and dopamine in the nucleus accumbens were studied with in vivo microdialysis using conscious, freely moving rats. 5-HT, dopamine, and their major metabolites were measured by HPLC with electrochemical detection. Amphetamine (1.0-9.0 mg/kg) elevated dopamine levels considerably, but failed to affect the levels of 5-HT, except at the highest dose administered. 3,4-Methylenedioxyamphetamine (MDA, 1.0-9.0 mg/kg) and 3,4-methylenedioxymethamphetamine (MDMA, 1.0-9.0 mg/kg) elevated both 5-HT and dopamine levels dose dependently. The failure of 2,5-dimethoxy-4-methylamphetamine (DOM, 0.5-1.0 mg/kg) to affect the 5-HT levels suggests that extracellular levels of 5-HT play a minor role in hallucinogenic activity. The strong effects of MDA and MDMA on levels of 5-HT indicate that their actions on serotonergic mechanisms are different from those of the hallucinogens. In addition, methylenedioxyamphetamines may act via dopaminergic mechanisms similar to those of amphetamine.

Detection and assay of cis- and trans-isomers of 4-methylaminorex in urine, plasma and tissue samples.

The 4-methylaminorex (4-MAX) is an amphetamine-related psychostimulant drug that has appeared on the clandestine market with a street name of "U4Euh". This compound exists as four stereoisomers, trans-4R,5R, trans-4S,5S, cis-4R,5S and cis-4S,5R, of which the cis forms have been classified as Schedule I substances in the US. The increasing variety of designer drugs has highlighted the importance of detection, identification, and quantitative measurement of these drugs, including 4-MAX, in biological samples. In the present study, the isomers of 4-MAX were detected in urine of rats treated with the drugs by some but not all of the on-site immunoassays tested, mainly as amphetamine or methamphetamine. To facilitate identification of 4-MAX by laboratories specialized in drug analysis, the electron-ionization mass spectrum and TLC data for underivatized 4-MAX using a routine laboratory drug-screening procedure is provided. In addition, a GC/MS method is described for the quantitative determination of cis- and trans-4-MAX as tert-butyldimethylsilyl-derivatives in plasma, urine and tissue.

PCR-sexing of bovine embryos: a simplified protocol.

To make bovine embryo sexing under farm conditions more feasible we developed a simplified protocol utilizing manual biopsy and detection of the Y chromosome directly from polymerase chain reaction (PCR) reaction tubes. Twenty-four embryos (morulae and blastocysts) were biopsied manually into 2 to 4 samples. One sample of each original embryo was diagnosed for sex, based on restriction fragment length polymorphism of PCR-amplified DNA of the ZFX/ZFY locus. The remaining 44 samples were diagnosed using the tube detection assay. In this assay the biopsies were pipetted into 0.5 -ml reaction tubes containing lysis mixture, incubated 10 to 60 min at 37 degrees C and inactivated 10 min at 98 degrees C. Then the PCR mixture was added containing buffer, DNA polymerase, ethidium bromide and primers designed to amplify the highly repeated btDYZ-1 region of the bovine Y chromosome. After 50 cycles of PCR, the reaction tubes were examined under UV illumination for pink fluorescence indicating the presence of Y-chromosomal DNA. All sexing results from the replicates were in agreement with the ZFX/ZFY assay, with 12 of the original embryos diagnosed as females and 12 as males. We conclude that highly efficient and accurate PCR-sexing of embryos can be accomplished without the use of micromanipulators, control primers and electrophoresis. The 2 reaction mixtures needed for sex diagnosis can be stored at -20 degrees C and -196 degrees C, respectively. The tube detection assay minimizes the risk of carryover contamination by previously amplified products as there is no need to open the tubes following PCR.

Rewarding properties of methylphenidate: sensitization by prior exposure to the drug and effects of dopamine D1- and D2-receptor antagonists.

In drug addiction, a sensitization phenomenon has been postulated to play a critical role. The aim of our study was to evaluate whether sensitization occurs to the rewarding properties of methylphenidate, a psychostimulant drug known to possess abuse potential, as assessed with the biased conditioned place preference method in rats. In addition, since the brain dopaminergic system is considered to be important in drug-reward, the involvement of dopamine D1- and D2-receptors both in the rewarding properties of methylphenidate and in sensitization to these properties was assessed. Conditioning with methylphenidate at doses of 1.25 to 20 mg/kg increased preference for the paired environment, whereas a dose of 0.31 mg/kg was ineffective. However, following the 7-day sensitization treatment with methylphenidate (0.62-20 mg/kg), conditioning with a dose of 0.31 mg/kg resulted in an increased preference for the paired environment, i.e., the rewarding properties of methylphenidate appeared to be sensitized. Control experiments indicated that the enhancement of preference was not due to attenuation of sensitization treatment-induced withdrawal nor to tolerance to aversive properties of methylphenidate. When conditioned with methylphenidate, D1-antagonist SCH 23390 but not D2-antagonist raclopride prevented place preference. However, when coadministered with methylphenidate during the sensitization treatment, both SCH 23390 and raclopride prevented the development of sensitization. These data indicate that the rewarding properties of methylphenidate are sensitized by prior exposure to the drug and that both D1- and D2-receptors, the latter of which possibly more specifically, appear to be involved in the development of this sensitization.

Oxalic acid stabilizes dopamine, serotonin, and their metabolites in automated liquid chromatography with electrochemical detection.

Use of antioxidative agents is required in automated LC assay of microdialysis samples, due to rapid degradation of the monoamine neurotransmitters and their metabolites. Addition of oxalic acid prevented degradation of dopamine, serotonin, 3,4-dihydroxyphenylacetic acid, homovanillic acid and 5-hydroxyindoleacetic acid efficiently: after a 24-h incubation at room temperature the decreases in peak heights were less than 10%. The long-term stability of the analytes, however, was still enhanced when acetic acid and L-cysteine were included in the solution. Using this antioxidative solution, the monoamine neurotransmitters and their metabolites could be determined with an automated LC assay even at room temperature.

Leukocytes as immunosensors: an immunoassay without labelled reagents.

A novel quantitative nonlabel immunoassay is described. It is based on the recognition of antigen-antibody complexes by the Fc-receptors of phagocytic leukocytes and the subsequent activation of these cells. Activation which is proportional to the amount of immune complexes present can be detected by measuring the intensity of chemiluminescence emitted by the activated cells. In addition to determinations of an antigen and an antibody, the binding capacity of complement to antigen-antibody complexes can be estimated.

5-HT3 receptor antagonist MDL 72222 dose-dependently attenuates cocaine- and amphetamine-induced elevations of extracellular dopamine in the nucleus accumbens and the dorsal striatum.

The effects of a 5-HT3 receptor antagonist MDL 72222 on cocaine- and amphetamine-induced increases in extracellular dopamine in the nucleus accumbens and the dorsal striatum were studied with microdialysis technique using halothane anaesthesized rats. Dopamine and its metabolites were measured by HPLC with electrochemical detection. Cocaine elevated extracellular dopamine in the nucleus accumbens and to a lesser extent in the dorsal striatum, but it did not affect dopamine metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid. Pretreatment with MDL 72222 (25-100 micrograms/kg) dose-dependently attenuated cocaine-induced elevation of dopamine in both of the nuclei studied. Amphetamine elevated extracellular dopamine and reduced DOPAC and homovanillic acid equally in the nucleus accumbens and in the dorsal striatum. MDL 72222 also attenuated the amphetamine-induced elevation of extracellular dopamine concentration in both brain areas studied, but first at a dose of 100 micrograms/kg. The different potencies of the interactions of the 5-HT3 receptor antagonist with cocaine and amphetamine could be related to the different mechanisms by which these drugs primarily elevate extracellular dopamine.