Karen_1998_Pestic.Biochem.Physiol_60_167

Brain acetylcholinesterase (AChE) inhibition was measured during 4-week and 4-day episodic exposures to chlorpyrifos. Organisms were exposed to a seawater (-) control, an acetone (+) control (0.1%), and 0.625, 1.25, 2.5, 5.0, and 10.0 ug of chlorpyrifos L-1 in each test. These episodic exposures significantly depressed AChE activity at 2.5, 5.0, and 10.0 ug L-1(weekly test) and at 1.25, 2.5, 5.0, and 10.0 ug L-1(daily test). Six-hour pulsed exposure to chlorpyrifos inhibited brain AChE activity at concentrations as low as 1. 25 ug L-1. Stress at failure of caudal vertebrae following episodic exposure was also tested. Analysis of samples from daily 6-h treatments found no differences after 2 days; however, vertebrae were significantly weaker (than controls) after 4 days. Analysis of weekly 6-h exposures found weaker caudal vertebrae after 2 weeks but not after 4 weeks.