The Physiological and Behavioural Adjustments of the Zebrafish 'Danio rerio' Exposed to the β-blocker Propranolol

Abstract

Propranolol (PROP) is a β-blocker prescribed mainly to treat human cardiac diseases but with its wide usage it often makes its way into the aquatic environment. This study examined whether PROP alters developmental patterns and catecholamine (CA)-regulated processes in the zebrafish (Danio rerio) and if exposure during early life alters the stress response and behaviors of adults. The 48 h LC50 was 21.6 mg/L, well above environmental levels (0.00059 mg/L). Embryos/larvae continuously PROP-exposed had decreased and increased transcript levels of the β1-adrenoceptor at 1 dpf and 5 dpf, respectively. Stressed, PROP-exposed zebrafish had reduced testosterone and estradiol levels and exhibited less anxiety behaviours than control fish. Furthermore, adults previously PROP-exposed as embryos/larvae had decreased growth in terms of body length (0.0006 mg/L PROP) and mass (20 mg/L PROP). Changes in cholesterol and testosterone levels occurred in PROP-exposed fish. Thus PROP-exposure alters developmental patterns and CA-regulated process that are essential for normal behaviours and responses to stress, and at least some of these changes persist in the adult zebrafish.