Cholinergic and Behavioral Neurotoxicity of Carbaryl and Cadmium to Larval Rainbow Trout (Oncorhynchus mykiss)

Abstract

Pesticides and heavy metals are common environmental contaminants that can cause neurotoxicity to aquatic organisms, impairing reproduction and survival. Neurotoxic effects of cadmium and carbaryl exposures were estimated in larval rainbow trout (RBT; Oncorhynchus mykiss) using changes in physiological endpoints and correlations with behavioral responses. Following exposures, RBT were videotaped to assess swimming speed. Brain tissue was used to measure cholinesterase (ChE) activity, muscarinic cholinergic receptor (MChR) number, and MChR affinity. ChE activity decreased with increasing concentrations of carbaryl but not of cadmium. MChR were not affected by exposure to either carbaryl or cadmium. Swimming speed correlated with ChE activity in carbaryl-exposed RBT, but no correlation occurred in cadmium-exposed fish. Thus, carbaryl exposure resulted in neurotoxicity reflected by changes in physiological and behavioral parameters measured, while cadmium exposure did not. Correlations between behavior and physiology provide a useful assessment of neurotoxicity.

Zinc and Calcium Supplementation to Combat Cadmium Induced Bioaccumulation in Fresh Water Teleost Oreochromis Mossambicus (Tilapia)

“…ATPase causing metabolic effects and disrupting neurotransmitter uptake [45]. In several situations, acetylcholine is not broken and accumulates within synapses causing physiologic impairment and alterations in fish swimming behavior [46] It is clear from the present study that the toxicity of metal is affected by Ca which in turn reduces the toxic effect of metal through competitive inhibition at the gill surface.…”

Cadmium disrupts behavioural and physiological responses to alarm substance in juvenile rainbow trout (Oncorhynchus mykiss)

“…This possibly explains why past studies have suggested that Cd does not alter normal fish behaviour by disrupting brain function (e.g. neurotransmitter levels; Beauvais et al, 2001).…”

Risks of carbamate and organophosphate pesticide mixtures to salmon in the Pacific Northwest

“…Although herbicides could indirectly affect salmonids via effects to algae and plants, direct effects to fish from these pesticides are much less likely. In contrast to the other pesticide groups, carbamates and organophosphate pesticides are highly toxic to salmonids (Beauvais et al 2000(Beauvais et al , 2001Sandahl and Jenkins 2002;Sandahl et al 2005;Laetz et al 2009;NOAA 2009) and were frequently detected in the Washington State WRIAs from 2003 to 2007. Thus, carbamate and organophosphate pesticides are the pesticides of greatest concern for direct effects to Pacific salmonids.…”

“…Inhibition of AChE activity occurs in the central nervous system (CNS) and in the plasma and muscle of fish (Perkins and Schlenk 2000). Studies with a number of carbamate and organophosphate pesticides (e.g., azinphosmethyl, chlorpyrifos, malathion, diazinon, carbaryl) have demonstrated an association between inhibition of brain AChE activity and behavioral endpoints such as reduction in spontaneous swimming and feeding rates, swimming stamina, predator detection, and homing behavior (Post and Leasure 1974;Moore and Waring 1996;Van Dolah et al 1997;Beauvais et al 2000Beauvais et al , 2001Scholz et al 2000;Sandahl et al 2005;Labenia et al 2007).…”