The effect of acetylcholinesterase inhibition on the release of acetylcholine from the striatum in vivo: interaction with autoreceptor responses.

The release of acetylcholine from the rat striatum is under inhibitory control of muscarinic autoreceptors. Since in vivo release studies are generally performed in the presence of an acetylcholinesterase inhibitor, modifications of responses to muscarinic receptor agonists and antagonists may be expected. In this study we show that the addition of 0.1 microM neostigmine bromide to the perfusion Ringer in a dialysis experiment attenuates the responses obtained by infusion of 100 microM oxotremorine and potentiates the effect of infusion of 1 microM atropine. Furthermore it is shown that under physiological conditions the muscarinic autoreceptors are not fully occupied, since infusion of 1 microM atropine did not affect the release of acetylcholine when no acetylcholinesterase inhibitor was added to the perfusion Ringer.