Reversal by atropine of tetanic fade induced in cats by antinicotinic and anticholinesterase agents.

The tetanic fade induced by intraarterial administration of neostigmine or by subparalyzing doses of d-tubocurarine or hexamethonium was studied in cat anterior tibial muscle preparations. The prior administration of atropine significantly reduced the time for recovery from the tetanic fade induced by the above mentioned drugs. A similar response was seen when atropine was administered prior to neostigmine administration for reversal of paralyzing doses of d-tubocurarine. We interpret these results to show that presynaptic muscarinic receptors participate in a negative feedback affecting acetylcholine release at the neuromuscular junction.