Higher physiological doses of nandrolone decanoate do not influence the Bezold-Jarish reflex control of bradycardia

Background. We investigated the influence of short-term treatment with supraphysiological doses of an anabolic-androgenic steroid on the Bezold-Jarisch reflex (BJR) control of heart rate (HR) and whether this treatment induced cardiac hypertrophy and anabolic effects in rats. Methods. Male rats were treated with nandrolone decanoate (10 mg/kg(-1) body weight/4 weeks; DECA) or vehicle control (CON). After 4 weeks of treatment, BJR was evaluated by bradycardia responses that were elicited by serotonin administration (2-32 mu g/kg(-1)). Mean arterial pressure (MAP) was assessed and cardiac hypertrophy was determined by the left ventricle weight/body weight (LVW/BW) ratio. Histological analyses of LV and the measurement of the total body protein content of the animals were performed. Results. Nandrolone decanoate (ND) treatment had no effect on the MAP (CON = 105 +/- 5; DECA = 110 +/- 3 mmHg). However, the mean basal HR of DECA animals was significantly lower than that of control animals (CON = 381 +/- 14; DECA = 324 +/- 12 bpm; p <0.01). ND did not change the sensitivity of the BJR. The LVW/BW ratio indicated significant hypertrophy of the LV in DECA animals (CON = 1.76 +/- 0.04; DECA = 2.0 +/- 0.04 mg/g; p < 0.01). Histological and morphometrical analyses demonstrate that there is also modest myocyte hypertrophy (CON = 14.5 +/- 1.5; DECA = 20.0 +/- 0.9 myocyte nuclei/field; p <0.05). However, the Masson-trichromic-stained samples showed an enhancement of collagen deposits on the LV matrix. Conclusions. We concluded that 4 weeks ND treatment induced an anabolic effect and the beginnings of LV remodeling, mainly due to excessive collagen deposition in the cardiac extracellular matrix. However, the treatment did not influence BJR control of bradycardia, an effect that could be explained by an enhanced efferent vagal tonus in DECA animals. (C) 2008 IMSS. Published by Elsevier Inc.