Alterações eletrocorticográficas, eletrocardiográficas e de cálcio sérico causadas por dose suprafisiológica de vitamina A

Abstract

Vitamin A and its derivatives are widely used therapeutically, primarily for skin and hair, due to its antioxidant activity that protects cells against damage caused by excess free radicals. Vitamin A acts on nuclear receptors and, as a result, increases gene expression. High doses of vitamin A and its derivatives can lead to changes in organ functions, such as osteoclastic activity and increased levels of serum calcium, which can precipitate osteopenia and osteoporosis. Little is known about its activity in the central nervous system; however, there have been reports of behavioral changes and the possibility of exacerbating depressive symptoms with an increased risk of suicide. There were used 45 male Wistar rats for this study, to which silver electrodes were implanted in the motor cortex (stereotactic coordinate of -0.96 from bregma). For the ECG examinations, the D2 lead was used, and subsequently, blood samples were collected from the animals for serum calcium measurement. The rats were treated with 50,000 IU/kg i.p. every 24 hours for 3, 7, and 14 days. Each group had its electrocorticographic (ECoG) activity, electrocardiographic (ECG) activity, and serum calcium levels evaluated. It was demonstrated that there was a gradual increase in serum calcium, but it remained within the normal range for the species. The ECoG revealed increased activity in low-frequency brain oscillation bands (delta, theta, and alpha). The cardiac activity was close to normal with a sinus rhythm and a decrease in the RR and QT intervals.