Treadmill exercise does not change gene expression of adrenal catecholamine biosynthetic enzymes in chronically stressed rats

Abstract

Chronic isolation of adult animals represents a form of psychological stress that produces sympathoadrenomedullar activation. Exercise training acts as an important modulator of sympatho-adrenomedullary system. This study aimed to investigate physical exercise-related changes in gene expression of catecholamine biosynthetic enzymes (tyrosine hydroxylase, dopamine-β-hydroxylase and phenylethanolamine N-methyltransferase) and cyclic adenosine monophosphate response element-binding (CREB) in the adrenal medulla, concentrations of catecholamines and corticosterone (CORT) in the plasma and the weight of adrenal glands of chronically psychosocially stressed adult rats exposed daily to 20 min treadmill running for 12 weeks. Also, we examined how additional acute immobilization stress changes the mentioned parameters.Treadmill running did not result in modulation of gene expression of catecholamine synthesizing enzymes and it decreased the level of CREB mRNA in the adrenal medulla of chronically psychosocially stressed adult rats. The potentially negative physiological adaptations after treadmill running were recorded as increased concentrations of catecholamines and decreased morning CORT concentration in the plasma, as well as the adrenal gland hypertrophy of chronically psychosocially stressed rats. The additional acute immobilization stress increases gene expression of catecholamine biosynthetic enzymes in the adrenal medulla, as well as catecholamines and CORT levels in the plasma.Treadmill exercise does not change the activity of sympatho-adrenomedullary system of chronically psychosocially stressed rats.

Impaired adrenal medullary function in a mouse model of depression induced by unpredictable chronic stress

“…This effect was not observed in rats under immobilization, in which TH mRNA, protein and activity remained elevated even after 41 stressor exposures (Nankova et al, 1994). Different changes in catecholamine biosynthetic enzymes were also observed when chronically stressed animals were exposed to the same (homotypic) or a novel stressor (heterotypic) (Gavrilovic et al, 2008(Gavrilovic et al, , 2013Sabban and Serova, 2007). Nevertheless, an increase in adrenal medulla size induced by chronic stress is often associated with increases in expression, synthesis and activity of catecholamine biosynthetic enzymes [see Kvetnansky et al (2009) for review].…”

Metabolomic analysis of long-term spontaneous exercise in mice suggests increased lipolysis and altered glucose metabolism when animals are at rest

“…This may indicate a lower rate of catecholamines synthesis by the adrenal glands after longterm spontaneous exercise. However, there is no evidence in the literature showing a significant training effect on adrenaline and noradrenaline resting values in animals (24,25) and human studies (40,44,52,62). There are several reports on the composition and content of amino acids in the blood of rodents undergoing forced exercise (35).…”

Avaliação comportamental de ratos treinados em natação forçada

“…Apesar de no presente estudo não ter sido realizada a dosagem hormonal, tal resultado é compatível com o que foi observado nos testes comportamentais, indicando que mesmo a natação forçada com sobrecarga foi insuficiente para produzir alterações na ansiedade dos animais. Já Gavrilovic et al [30] observaram que ratos estressados por isolamento social e que realizaram exercício em esteira por 12 semanas (iniciando com 10 minutos na velocidade de 10 metros por minuto e aumentando até 20 minutos na velocidade de 20 metros por minuto), não apresentaram redução nas concentrações de catecolaminas e corticosterona plasmáticas, nem hipertrofia adrenal. Ainda, Fuss et al [18] relatam que em camundongos exercitados voluntariamente, por corrida em esteira, apesar de maiores concentrações de Fator Neurotrófico Derivado do Cérebro (BDNF, Brain-Derived Neurotrophic Factor) e neurogênese no hipocampo, apresentaram aumento no comportamento de ansiedade e maiores níveis de corticosterona (indicativos de estresse) em suas fezes.…”

“…O exercício físico tem sido testado para aliviar diversos tipos de estresse experimentalmente induzidos, como isolamento social [5,30], ruídos [35], imobilização, frio [31], privação de alimentos e água [14], dentre outros. Há indícios de que o tipo e a intensidade do exercício, bem como o modelo animal utilizado, podem influenciar nas respostas hormonais e comportamentais [36].…”