Neurobehavioral impairments caused by developmental imidacloprid exposure in zebrafish

Abstract

BACKGROUND Neonicotinoid insecticides are becoming more widely applied as organophosphate (OP) insecticides are decreasing in use. Because of their relative specificity to insect nicotinic receptors, they are thought to have reduced risk of neurotoxicity in vertebrates. However, there is scant published literature concerning the neurobehavioral effects of developmental exposure of vertebrates to neonicotinoids. METHODS Using zebrafish, we investigated the neurobehavioral effects of developmental exposure to imidacloprid, a prototypic neonicotinoid pesticide. Nicotine was also administered for comparison. Zebrafish were exposed via immersion in aqueous solutions containing 45 μM or 60 μM of imidacloprid or nicotine (or vehicle control) from 4 h to 5 d post fertilization. The functional effects of developmental exposure to both imidacloprid and nicotine were assessed in larvae using an activity assay and during adolescence and adulthood using a battery of neurobehavioral assays, including assessment of sensorimotor response and habituation in a tactile startle test, novel tank swimming, and shoaling behavior. RESULTS In larvae, developmental imidacloprid exposure at both doses significantly decreased swimming activity. The 5D strain of zebrafish were more sensitive to both nicotine and imidacloprid than the AB* strain. In adolescent and adult fish, developmental exposure to imidacloprid significantly decreased novel tank exploration and increased sensorimotor response to startle stimuli. While nicotine did not affect novel tank swimming, it increased sensorimotor response to startle stimuli at the low dose. No effects of either compound were found on shoaling behavior or habituation to a startling stimulus. DISCUSSION Early developmental exposure to imidacloprid has both early-life and persisting effects on neurobehavioral function in zebrafish. Its developmental neurotoxicity should be further investigated.

Neurotoxicity of a Biopesticide Analog on Zebrafish Larvae at Nanomolar Concentrations

“…We show that exposure of zebrafish larvae to A6 induces larval mortality at the relatively low concentration of 0.5 μM, with marked effects on the nervous system, both central and sensory. Similar lethalities have been reported for other pesticides tested on zebrafish larvae [35,36,37]. Using the well-defined and easily accessible lateral line sensory system as an assay, we observed that A6 affects axonal regeneration at the low dose of 50 nM, suggesting that this compound may have serious long-term effects on neural plasticity and repair at these low doses.…”

Effects of neonicotinoids on putative escape behavior of juvenile wood frogs (Lithobates sylvaticus) chronically exposed as tadpoles

“…There is also the possibility that the neonicotinoids have affected the anxiety of the wood frogs because nAChRs, where neonicotinoids bind in the nervous system, are involved in anxiety-like behaviors in mice (Drago et al 2003). Crosby et al (2015) conducted the first targeted assessment of the behavioral effects of imidacloprid on an aquatic vertebrate, using a fish model species, the zebrafish (Danio rerio). They assessed the developmental neurotoxicity of larval aquatic exposure to imidacloprid (and nicotine) on zebrafish as larvae immediately after exposure and during adolescence and adulthood after exposure had ceased for 1.5 and 3 mo, respectively (Crosby et al 2015).…”

Developmental neurotoxicity of succeeding generations of insecticides

“…Recently, we (Crosby and others 2015) investigated in zebrafish the neurobehavioral effects of developmental exposure to imidacloprid, a prototypic neonicotinoid pesticide. Nicotine was also administered for comparison.…”