Aquatic Toxicology 116–117 (2012) 8–15 Contents lists available at SciVerse ScienceDirect Aquatic Toxicology jou rn al h om epa ge: www.elsevier.com/locate/aquatox Effects of exposure to the -blocker propranolol on the reproductive behavior and gene expression of the fathead minnow, Pimephales promelas Varenka Lorenzi a , Alvina C. Mehinto b , Nancy D. Denslow b , Daniel Schlenk a,∗ a Department of Environmental Sciences, University of California Riverside, Riverside, CA, USA b Center for Environmental and Human Toxicology and Department of Physiological Sciences, University of Florida, Gainesville, FL, USA a r t i c l e i n f o Article history: Received 6 December 2011 Received in revised form 28 February 2012 Accepted 1 March 2012 Keywords: Pharmaceutical Reproduction Behavior Fish Microarray a b s t r a c t Human pharmaceutical drugs have been found in surface waters worldwide, and represent an increasing concern since little is known about their possible effects on wildlife. Propranolol is a common beta- adrenergic receptor antagonist (-blocker) typically prescribed to people suffering from heart disease and hypertension. Propranolol has been detected in United States wastewater effluents at concentrations ranging from 0.026 to 1.90 g/l. In mammals, there is evidence that -blockers can cause sexual dysfunc- tion, and alter serotonergic pathways which may impact reproductive behavior but little is known about the effects on fish behavior. The present study tested the effects of propranolol on fecundity, on brain gene expression and on reproductive behavior of the fathead minnow, Pimephales promelas, a fish that exhibits male parental care. Sexually mature fathead minnows were housed at a ratio of one male and two females per tank and exposed to nominal concentrations of 0, 0.1, 1, 10 g/l for 21 days. Measured con- centrations (±SD) of propranolol were 0.003 ± 0.004, 0.05 ± 0.02, 0.88 ± 0.34 and 4.11 ± 1.19 g/l. There were no statistically significant differences in fecundity, fertilization rate, hatchability and time to hatch. Propranolol exposure was not associated with a change in nest rubbing behavior, time spent in the nest or approaching the females. There was a significant difference in the number of visits to the nest with males receiving low and medium propranolol treatments. The microarray analysis showed that there were 335 genes up-regulated and 400 genes down-regulated in the brain after exposure to the highest dose of propranolol. Among those genes, myoglobin and calsequestrin transcripts (fold change = 10.84 and 5.49, respectively) were highly up-regulated. Ontological analyses indicated changes in genes involved in calcium ion transport, transcription, proteolysis and apoptosis/anti-apoptosis. Pathway analysis indi- cated that the reduced expression of caspases may lead to impaired neurite outgrowth, neurotransmitter secretion and brain function in developing organisms. The results showed that exposure to propranolol at concentrations as high as 4.11 g/l did not significantly impact reproductive behavior or spawning abilities of fathead minnow but did alter the regulation of genes within the brain of fish. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Beta blockers (-blockers) are a class of drugs used to treat cardiac arrhythmias and hypertension. They act as antagonists of the beta adrenergic receptors inhibiting the normal epinephrine- mediated sympathetic actions that would cause an increase in cardiac output. Propranolol is a non-specific  1 ,  2 -blocker and it is very commonly prescribed worldwide. It was identified in munic- ipal wastewater effluents at a maximum concentration of 1.9 g/l in the United States (Huggett et al., 2003), and up to 590 ng/l in European countries (Ternes, 1998; Andreozzi et al., 2003). ∗ Corresponding author at: 2258 Geology Building, 900 University Ave, Depart- ment of Environmental Sciences, University of California Riverside, Riverside, CA 92521, USA. Tel.: +1 951 827 7065; fax: +1 951 827 3993. E-mail address: Daniel.schlenk@ucr.edu (D. Schlenk). Beta-blockers taken as antihypertensive medication have been reported to be associated with sexual dysfunction in men (Burnett and Chanine, 1979; Fogari and Zoppi, 2002). Treatment of healthy men with propranolol was associated with a significant decrease in testosterone levels (Rosen et al., 1988). Similar effects were found in rodent studies, where propranolol inhibited sexual behav- ior in male rats (Smith et al., 1990). Propranolol can also bind to serotonin (5-HT) receptors in the brain, and act as an antag- onist at these sites (Middlemiss, 1984; Sprouse and Aghajanian, 1986). Treatment of rat cultured Leydig cells with propranolol increased the level of 5-HT with consequent release of corti- cotropin releasing factor (CRF) and inhibition of steroidogenesis (Tinajero et al., 1992). The inhibitory effects of propranolol on male rat sexual behavior, and the impairment of sexual func- tion in men may be due to its serotonergic action rather than its antagonistic properties on the adrenergic system (Smith et al., 1996). 0166-445X/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.aquatox.2012.03.001