Relating olfactory neurotoxicity to altered olfactory-mediated behaviors in rainbow trout exposed to three currently-used pesticides.
Odor-evoked neurophysiological responses can form the basis for behavioral responses. Here we first characterized olfactory-mediated behavioral and neurophysiological responses of juvenile rainbow trout to the amino acid l-histidine, then looked at whether there were similar responses to the carbamate antisapstain IPBC and the herbicides atrazine and Roundup, and lastly explored how exposures to these pesticides modified the l-histidine responses. Trout were behaviorally attracted to 10(-7)M l-histidine (as assayed in a counter-current olfactometer), but this preference behavior switched to indifference with higher histidine concentrations. Neurophysiologically, the summed electrical responses of peripheral olfactory neurons, as measured using electro-olfactogram (EOG), was 0.843+/-0.252 mV to 10(-7)M l-histidine. Of the pesticides, only Roundup evoked EOGs, indicating the amino acid-based pesticide may have acted as an odorant, and generated a behavioral response: it was avoided at active ingredient [AI; glyphosate isopropyl amine] concentrations > or =10 mg/l. With 30 min pesticide exposures, 10(-7)M l-histidine preference behavior was eliminated following exposure to 1 microg/l IPBC and atrazine, and 100 microg/l AI Roundup. Similarly, 10(-7)M l-histidine-evoked EOGs were significantly reduced by exposure to 1 microg/l IPBC, 10 microg/l atrazine, and 100 microg/l AI Roundup. When combined together, the results demonstrate that typical preference behavior can be abolished when neurophysiological responses are reduced by >60% of control. This asymmetry in response thresholds suggests that behavioral responses may be more sensitive toxicological endpoints than neurophysiological responses.
Tierney
Keith B
KB
Department of Biological Sciences, Simon Fraser University, Burnaby, BC V5A 1S6, Canada.
Singh
Christopher R
CR
Ross
Peter S
PS
Kennedy
Christopher J
CJ
D000818:Animals; D001280:Atrazine / Q000633:toxicity*; D001522:Behavior, Animal / Q000187:drug effects; D002219:Carbamates / Q000633:toxicity*; D004594:Electrophysiology; D005998:Glycine / Q000031:analogs & derivatives* / Q000633:toxicity; D006639:Histidine / Q000494:pharmacology; D018034:Olfactory Receptor Neurons / Q000187:drug effects* / Q000502:physiology; D017686:Oncorhynchus mykiss / Q000502:physiology*; D010575:Pesticides / Q000633:toxicity*; D012903:Smell / Q000187:drug effects; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000633:toxicity; D000097797:Glyphosate
D001280:Atrazine; D002219:Carbamates; D005998:Glycine; D006639:Histidine; D010575:Pesticides; D014874:Water Pollutants, Chemical; D000097797:Glyphosate; C106572:3-iodo-2-propynylbutylcarbamate