Pyriproxyfen is one of the most used larvicides and
insecticides; it acts as an analog of juvenile
insect hormone (a growth regulator). It is highly toxic during all stages of mosquito development, suppresses metamorphosis, and interferes in insect reproduction and proliferation.
Pyriproxyfen and its main metabolite have been shown to affect brain development in rodents. This compound is employed mainly to eliminate outbreaks of the genus Aedes, even in
potable water. Despite the increasing number of toxicological studies about larvicides and
insecticides-with an indication of continuous use-there have been few studies about the effects of
pyriproxyfen in non-target species such as fish. This study evaluated the effects of
pyriproxyfen on behavioral, cognitive, and endocrine parameters in zebrafish. We exposed adult zebrafish to different
pyriproxyfen (Pestanal®) concentrations (0.125, 0.675, and 1.75 mg/l) for 96 h. We analyzed behavioral parameters, memory,
cortisol levels, and gene expression of
glucocorticoid receptor (gr) and
corticotrophin-releasing factor (crf) after
pyriproxyfen exposure. This exposure did not alter locomotion (distance or mean speed), anxiety-like behavior (latency to enter to the top zone of the tank or time in the top zone of the tank), and social or aggressive behavior. However, there was impaired inhibitory avoidance memory at all tested
pyriproxyfen concentrations.
Cortisol levels were reduced in exposed groups when compared to control or vehicle. However, gr and crf gene expression in
pyriproxyfen-treated animals were unaltered when compared to control or vehicle groups. Taken together, these findings indicate that
pyriproxyfen may induce
cognitive impairment and altered
cortisol levels in zebrafish, a non-target species.