Early life adversity can disrupt development leading to emotional and cognitive disorders. This study investigated the effects of social isolation after weaning on anxiety, body weight and locomotion, and on extracellular dopamine (DA) and glutamate (GLU) in the nucleus accumbens (NAc) and their modulation by corticotropin releasing factor receptor 1. On the day of weaning, male rats were housed singly or in groups for 10 consecutive days. Anxiety‐like behaviors were assessed by an elevated plus maze (EPM) and an open field test (OF). Neurotransmitter levels were measured by in vivo microdialysis. Single‐housed rats spent less time, and entered more, into the closed arms of an EPM than group‐housed rats. They also spent less time in the center of an OF, weighed more and showed greater locomotion. In the NAc, no differences in CRF, or in basal extracellular DA or GLU between groups, were observed. A depolarizing stimulus increased DA release in both groups but to higher levels in isolated rats, whereas GLU increased only in single‐housed rats. Blocking CRF‐R1 receptors with CP‐154,526 decreased DA release in single‐housed but not in group‐housed rats. The corticotropin releasing factor receptor type 1 receptor antagonist also decreased GLU in group‐housed animals. These results show that isolating adolescent rats increases anxiety, body weight and ambulation, as well as the sensitivity of dopaminergic neurons to a depolarizing stimulus. This study provides further evidence of the detrimental effects of social isolation during early development and indicates that dysregulation of the CRF system in the NAc may contribute to the pathologies observed.

Methods were developed with a view to evaluating various sample preparation systems for use with X-ray fluorescence techniques in order to determine the major and minor components of ferroalloys, which are used as alloy-forming elements in steel making. The methods were compared in terms of simplicity and rapidity and these parameters were assessed in relation to the accuracy and precision of the results. The samples were prepared in three formats: metal samples, by dilution with iron and remelting in an induction furnace; pellets, by direct compaction of the ground material, and beads, by alkaline melting of the pre-oxidized sample. The tests used to optimize these methods were conducted with commercial ferroalloys, previously characterized by employing wet chemical and spectroscopic methods. Reproducibility and precision studies were conducted on samples obtained using each of the three sample preparation systems. The precisions (relative standard deviations) of major element determinations were <0.8, <1.0 and < O S % and those for minor elements were <5, <5 and <3% for metal samples, pellets and beads, respectively. The accuracy of the methods was checked by analysing reference materials of each type of ferroalloy.

A study of chromium determination in ferrochromium by X-ray fluorescence and spark ablation inductively coupled plasma atomic emission spectrometry was made. Bulk test samples were prepared by re-melting the ferroalloy diluted with iron in an induction furnace. Calibration samples were obtained from an industrial ferroalloy, using different FeCr + Fe dilution ratios, in order to cover the chromium concentration range that is probably present in these materials. A study is presented of the influence of the carbon contents on Cr Kcu line intensities and on the amount of spark aerosol produced, as well methods of compensating for the effect. The total variance and the average instrumental variation were calculated from the values obtained for samples with the same chromium concentration and variable carbon contents. The criterion applied to test the agreement of the two methods showed that the difference between the results provided by both techniques can be explained by random errors. Accuracies were tested by analysing a series of ferrochromium reference materials.

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Adolescence is a developmental period characterized by neuronal growth. Environmental factors such as maternal neglect, social stress and drugs of abuse have a direct impact on future behavioral patterns. Because rats are highly social animals, we decided to investigate if isolation stress during adolescence increases conditioned place preference (CPP) to drugs of abuse. Since lower D2 receptor expression in the mesocorticolimbic system is known to increase cocaine conditioning in adult animals, and because adolescents and adults differ in dopaminergic connectivity and D2 receptor populations, we investigated if D2 receptors are altered during these conditions. Female rats were weaned at postnatal day 23 and housed singly or in pairs. At day 34 rats were tested in an open field, at day 35 in an elevated plus maze and at day 36 they were tested for CPP to cocaine (15mg/kg). At post‐natal day 48, rats were euthanized, brains collected and stored at −80°C. Single‐housed rats showed greater conditioning to cocaine when compared to group‐housed rats. This suggest that housing rats singly increases the rewarding properties of cocaine. Single‐housed rats also show lower D2 receptor immunoreactivity in the Nucleus accumbens (NAc) and the Prefrontal cortex (PFC) when compared to group‐housed rats. This correlates with the greater conditioning observed in single housed rats. Isolation stress had the effect of lowering D2 receptor populations in the NAc and PFC thus augmenting the rewarding properties of cocaine in adolescent female rats. Chronic stress during adolescence thus can lower D2 receptors and could be a determining factor in substance abuse and relapse. Support or Funding Information Financial assistance was provided by the Office of International Science and Engineering (OISE) of NSF through the Partnerships for Research and Education (PIRE) Program (OISE‐#1545803).