Muscarinic receptor activation inhibits both release and synthesis of noradrenaline in rat hippocampal synaptosomes.
Rat hippocampal synaptosomes were used to investigate the effects of muscarinic cholinergic drugs on the release of [(3)H]noradrenaline and the rate of noradrenaline synthesis. Oxotremorine and acetylcholine caused depression of K(+)-evoked release of [(3)H]noradrenaline; these effects were reversed by atropine and pirenzepine. Muscarinic agonists depressed 2-chloroadenosine- and isoprenaline-stimulated noradrenaline synthesis but had no effect on 8-Br-cyclic AMP-stimulated synthesis. Oxotremorine also depressed the K(+)-acceleration of noradrenaline synthesis. The action of pirenzepine suggests that the inhibition of release and synthesis are mediated by separate muscarinic receptor subtypes.
Birch
P J
PJ
University Laboratory of Physiology, Parks Road, Oxford OX1 3PT, U.K.
Fillenz
M
M