EFFECTS OF VARIOUS DRUGS INCLUDING ORGANOPHOSPHORUS COMPOUNDS (OPC) AND THERAPEUTIC COMPOUNDS AGAINST OPC ON DRL RESPONDING

The effects of various drugs were assessed in rats responding under a Differential-Reinforcement-of-low-Rate 30-s (DRL 30-s) schedule. Atrop ine, scopolamine, and CEB-1957 (a new muscarinic blocker) increased re sponse rate and decreased reinforcement rate, while methylatropine onl y decreased reinforcement rate. Physostigmine decreased response and r einforcement rates, when pyridostigmine had few effect on DRL respondi ng. The irreversible acetylcholinesterase (AChE) inhibitors organophos phorus compounds (OPC) soman and sarin, injected at one-third of the L DS, did not consistently alter DRL performance, suggesting that they p roduce few behavioral effects in the rat when administered at subtoxic doses. Three oximes-pralidoxime, pyrimidoxime, and HI-6-decreased bot h response and reinforcement rates. Mecamylamine had few consistent ef fects on performance, and nicotine, d-amphetamine, diazepam, and the w akening drug modafinil increased response rate and decreased reinforce ment rate. These two latter drugs also increased the number of very pr emature responses. These results, taken together, indicate that a DRL schedule is a useful tool to bring to light the existence of psychotro pic effects of a drug. The explanation of drug-induced alterations of DRL performance, in terms of effects on cognition or on mood, is also discussed. (C) 1998 Elsevier Science Inc.