NEONATAL EXPOSURE TO A TYPE-I PYRETHROID (BIOALLETHRIN) INDUCES DOSE-RESPONSE CHANGES IN BRAIN MUSCARINIC RECEPTORS AND BEHAVIOR IN NEONATAL AND ADULT MICE

This study shows that neonatal exposure to the insecticide bioallethri n has a dose-dependent effect on muscarinic cholinergic receptors (MAC hR) in the neonatal mouse, leading to permanent changes in MAChR and i n spontaneous behaviour in adult mice. Neonatal NMRI mice, given oral doses of either bioallethrin or the vehicle, once daily between the 10 th and 16th postnatal day, were killed at the age of 17 days or 1 week after the spontaneous motor behaviour tests at 4 months. The MAChR we re assayed in the cerebral cortex by using the antagonist quinuclidiny l benzilate ([H-3]QNB) and the agonist carbachol. In the 17-day-old mi ce bioallethrin exposure elicited a significant dose-dependent increas e in the specific [3H]QNB binding. The competition study showed that t he proportion of low-affinity binding was significantly increased in t he 17-day-old mice compared with controls. In the adult mouse there wa s a significant dose-dependent decrease in specific [3H]QNB binding. I n these adult mice the behavioural variables 'locomotion' and 'total a ctivity' showed significant (P less than or equal to 0.01) dose-depend ent increases at all doses up to and including 0.70 mg/kg b.wt.