ABSTRACT
<p><b>OBJECTIVE</b>To explore the effect of organophosphorus insecticides (OPs) on the nicotinic autoreceptor function (NAF) in rat cortical synaptosomes and to understand alternative target of the OPs for human and other animals.</p><p><b>METHODS</b>In vitro experiment, synaptosomes from the rats were incubated with [(3)H] choline and then superfused with physiological buffer. The [(3)H] acetylcholine release from the synaptosomes after the addition of paraoxon or chlorpyrifos to the superfusion system was recorded and the changes of NAF were calculated. In vivo experiment, NAF and acetylcholinesterase (AChE) activity in the cortical synaptosomes in the adult rats dosed with chlorpyrifos were also determined 96 h after OPs treatment.</p><p><b>RESULTS</b>Paraoxon caused slight effect on NAF (average inhibition rate: < 23%) while chlorpyrifos oxon caused > 100% of inhibition on NAF in vitro. Chlorpyrifos markedly reduced NAF by 66% 96 h after treatment and inhibited the AChE activity by 91% in vivo.</p><p><b>CONCLUSION</b>The OPs may have different effects on the NAF of rat cortical synaptosomes while chlorpyrifos may certainly inhibit the NAF in cortical synaptosomes of adult rats.</p>