title: Behavioral effects of type II pyrethroid cyhalothrin in rats.
abstract: Synthetic pyrethroids such as cyhalothrin are extensively used in agriculture for the control of a broad range of ectoparasites in farm animals. It has been suggested that type II pyrethroids might induce anxiogenic-like effects in laboratory animals. The present study was undertaken to investigate a possible anxiogenic-like outcome of cyhalothrin in rats. Adult male rats were orally dosed for 7 days with 1.0, 3.0, or 7.0 mg/kg/day of cyhalothrin, present in a commercial formulation (Grenade Coopers do Brazil S.A.). The neurobehavioral changes induced by cyhalothrin as well as those produced on corticosterone serum levels were measured 24 h after the last treatment. Picrotoxin (1.0 mg/kg) was also acutely used as a positive control for anxiety. Results showed that cyhalothrin: (1) induced some signs and symptoms of intoxication that included salivation, tremors, and liquid feces; (2) reduced total locomotor activity in the open-field; (3) reduced the percentage of time spent in open-field central zones; (4) increased immobility time in the open-field; (5) reduced the percentage of time spent in plus-maze open arms exploration; (6) reduced the time spent in social interactions, and (7) increased the levels of serum corticosterone. The behavioral changes reported for cyhalothrin (3.0 mg/kg/day) were similar of those induced by picrotoxin. The no effect level dose obtained for cyhalothrin in this study was 1.0 mg/kg/day. These results provide experimental evidence that cyhalothrin induces anxiety-like symptoms, with this effect being dose-related. Thus, anxiety must be included among the several signs and symptoms of pesticide intoxication.
authors.affiliation: Applied Pharmacology and Toxicology Laboratory, School of Veterinary Medicine, University of São Paulo, São Paulo, SP, Brazil, 05508-900.
authors.forename: D Abbud
authors.initials: DA
authors.lastname: Righi
authors.forename: J
authors.initials: J
authors.lastname: Palermo-Neto
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D000697:Central Nervous System Stimulants / Q000633:toxicity; D003345:Corticosterone / Q000097:blood; D004305:Dose-Response Relationship, Drug; D007306:Insecticides / Q000633:toxicity*; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D009043:Motor Activity / Q000187:drug effects; D009570:Nitriles; D019055:No-Observed-Adverse-Effect Level; D010852:Picrotoxin / Q000633:toxicity; D011722:Pyrethrins / Q000633:toxicity*; D051381:Rats; D017208:Rats, Wistar; D012919:Social Behavior
chemical_list: D000697:Central Nervous System Stimulants; D003345:Corticosterone; D007306:Insecticides; D009570:Nitriles; D010852:Picrotoxin; D011722:Pyrethrins; C037304:cyhalothrin