Effects of pyrethroid insecticides on operant responding maintained by food

Abstract

The pyrethroids are potent insecticides with low concomitant mammalian lethality when compared with other major insecticides. While high doses can lead to hyperactivity, tremors, convulsion and death, low doses have not been as well studied. Since operant behavior can be a sensitive measure of CNS function, male Holtzman rats were trained on a VR25 schedule maintained by 45 mg food pellets. Rats were injected IP with one of four different technical grade pyrethroids: permethrin, allethrin, deltamethrin and fenvalerate. All agents were effective in reducing operant responding and did so in a dose-dependent manner at levels 10 to 100 times below their LD50 values. Time course studies indicated a relatively short duration of action for the Type I agents of less than 60 min for permethrin and 15 min for allethrin. Type II agents were generally effective for greater than 60 min. Results of these studies indicate that operant responding maintained by food is a sensitive measure of the behaviorally disruptive effects of subconvulsive doses of pyrethroids.