Cholinergic involvement in the action of formetanate on operant behavior in rats

Parameters for Carbamate Pesticide QSAR and PBPK/PD Models for Human Risk Assessment

Our interest in providing parameters for the development of quantitative structure physiologically based pharmacokinetic/pharmacodynamic (QSPBPK/PD) models for assessing health risks to carbamates (USEPA 2005) comes from earlier work with organophosphorus (OP) insecticides (Knaak et al. 2004). Parameters specific to each carbamate are needed in the construction of PBPK/PD models along with their metabolic pathways. Parameters may be obtained by (1) development of QSAR models, (2) collecting pharmacokinetic data, and (3) determining pharmacokinetic parameters by fitting to experimental data. The biological parameters are given in Table 1 (Blancato et al. 2000). Table 1 Biological Parameters Required for Carbamate Pesticide Physiologically Based Pharmacokinetic/Pharmacodynamic (PBPK/PD) Models.(a).

Acute effects of the organophosphate paraoxon on schedule-controlled behavior and esterase activity in rats: dose-response relationships

The effects of acute intraperitoneal administration of paraoxon on behavioral and biochemical parameters were studied in male rats. Rats were trained to press a lever under an FR10 schedule of reinforcement. Rats were injected with 3 sublethal doses of paraoxon (0.5, 0.75, and 1.0 mg/kg) and performance was monitored for four days after exposure. Response rates were depressed significantly for days 1 and 2 with 0.75 and 1.0 mg/kg, but not 0.5 mg/kg, even though there was inhibition of brain and plasma cholinesterases at all doses. Performance recovered prior to brain AChE recovery. There was no clear-cut threshold of brain AChE inhibition required to yield performance deficits, nor was there a direct correlation between significant inhibition in peripheral enzymes which could serve as markers (plasma aliesterases, butyrylcholinesterase, non-iso-OMPA-sensitive cholinesterase, and hepatic aliesterases) and performance deficits, suggesting that other noncholinergic targets may play a role in OP-induced behavioral deficits.