Unreliability of EDTA samples for measuring bioamine neurotransmitter levels in cats.

OBJECTIVES: The aim of this study was to assess the reliability of an EDTA-based method for measuring cat blood bioamines. METHODS: Test 1 involved collecting blood samples from seven university laboratory cats. The samples were transferred to EDTA, heparin and plain tubes to determine concentrations of four bioamines (serotonin, dopamine, epinephrine [adrenaline] and norepinephrine [noradrenaline]). Correlation of measurements performed on EDTA plasma, with those performed on heparinized plasma or serum were assessed by intraclass correlation coefficients (ICCs). In test 2, blood samples from five owned cats were collected and stored in EDTA tubes and divided between duplicate Eppendorf tubes labeled as different cats for blinding purposes and analyzed independently for the same four bioamines as in test 1. Reliability of concentration determination for these duplicates was assessed by ICCs and coefficients of variation (CVs). RESULTS: In test 1, there was no significant correlation between the EDTA plasma serotonin and serum serotonin concentrations. There was also no significant correlation between EDTA plasma and heparin plasma concentrations for either epinephrine or norepinephrine. There was a statistically significant but weak correlation between EDTA plasma and heparin plasma dopamine concentrations. In test 2, there was no correlation for repeat-analyzed serotonin and epinephrine concentrations. Although there were statistically significant correlations for dopamine and norepinephrine, CVs for each analyte were in excess of 30%. CONCLUSIONS AND RELEVANCE: Before any further attempt is made to measure and report on neurotransmitter concentrations in domestic cats, it is essential that the robustness of the methodology is carefully validated and the data presented.

Modulatory action of environmental enrichment on hormonal and behavioral responses induced by chronic stress in rats: Hypothalamic renin-angiotensin system components.

Environmental enrichment (EE) has been studied as a protocol that can improve brain plasticity and may protect against negative insults such as chronic stress. The aim of this study was to evaluate the effects of EE on the hormonal and behavioral responses induced by chronic mild unpredictable stress (CMS) in rats, considering the involvement of the renin-angiotensin system. Male adult rats were divided into 4 groups: control, CMS, EE, and CMS + EE, and the experimental protocol lasted for 7 weeks. EE was performed during 7 weeks, 5 days per week, 2 h per day. CMS was applied during weeks 3, 4, and 5. After the CMS (week 6), depression-like behavior was evaluated by forced swimming and sucrose consumption tests, anxiety level was evaluated using the elevated plus-maze test, and memory was evaluated using the Y-maze test. On week 7, the animals were euthanized and basal plasma levels of corticosterone and catecholamines were determined. The hypothalamus was isolated and tissue levels of angiotensin peptides were evaluated. CMS increased plasma corticosterone, norepinephrine, and epinephrine basal concentrations, induced depression-like behaviors, impaired memory, and increased hypothalamic angiotensin I, II, and IV concentrations. EE decreased stress hormones secretion, depression-like behaviors, memory impairment, and hypothalamic angiotensin II induced by stress. Reductions of anxiety-like behavior and norepinephrine secretion were observed in both stressed and unstressed groups. The results indicated that EE seemed to protect adult rats against hormonal and behavioral CMS effects, and that the reduction of angiotensin II could contribute to these effects.