Differential alterations of cholinergic muscarinic receptors during chronic and acute tolerance to organophosphorus insecticides

Effect of single or chronic injection with a carbamate, propoxur, on the brain cholinergic system and behavior of mice.

“…Chronic treatment with carbamates and organophosphorus com pounds causes behavioral modifications such as changes in memory and learning ability and affects the cholinergic system such as causing changes in HAChT and [3H] QN B binding (28)(29)(30)(31)(32)(33)(34). We speculate that there is some relationship between the change in HAChT or [3H]QNB binding and rotarod performance in the present experiments.…”

Differential Modulation of Muscarinic Receptors in the Rat Brain by Repeated Exposure to Methyl Parathion.

“…Several pervious in vivo studies reported a reduction in the number of muscarinic receptors in certain brain areas as a result of chronic exposure to various OPs (Schiller, 1979;Costa et al, 1982;Russell and Overstreet, 1987).…”

“…Muscarinic receptor subtypes differ in synaptic and tissue localization, agonist and antagonist affinity, and the second messenger systems associated with them (Caulfield and Birdsall, 1998). By far the most common and consistent finding on repeated exposure to OP antiAChEs has been a reduction in the number of mAChRs (Schiller, 1979;Costa et al, 1982;Yamada et al, 1983;Churchill et al, 1984aChurchill et al, , 1984b. It has been suggested as the primary mechanism by which animals adapt to or compensate for sustained mAChR activation (Russell and Overstreet, 1987;Hoskins and Ho, 1992).…”

Acetylcholinesterase and Acetylcholine Receptors: Brain Regional Heterogeneity

“…By far the most common and consistent finding among the reports on chronic exposure to organophosphate compounds has been a reduction in the number of muscarinic AChRs 1.5 EFFECTS ON ACETYLCHOLINE RECEPTORS (Churchill et al, 1984a(Churchill et al, , 1984bCosta et al, 1982aCosta et al, , 1982bGupta et al, 1985;Kobayashi et al, 2007;Russell and Overstreet, 1987;Schiller, 1979;Sun et al, 2003;Yamada et al, 1983). Previous studies have shown that repeated postnatal exposure of rats to organophosphates resulted in persistent inhibition of brain AChE and transient reductions of total and M2/M4 mAChR (Liu et al, 1999;Tang et al, 1999).…”

“…These homeostatic mechanisms involve modulation of both presynaptic and/or postsynaptic components of the cholinergic synapse. These may involve changes in HACU, ChAT, and the vesicular VAChT in the presynaptic terminal and modifications of mAChRs and nAChRs for both the postsynaptic and presynaptic components (Costa et al, 1981a(Costa et al, , 1981b(Costa et al, , 1982a(Costa et al, , 1982bKobayashi et al, 1986Kobayashi et al, , 1997Padilla, 1995;Richardson and Chambers, 2003Russell and Overstreet, 1987;Schwab et al, 1981Schwab et al, , 1983Whalley and Shih, 1988).…”