ACETYLCHOLINE SENSITIVITY OF CAT'S MEDULLARY NEURONS

Abstract

The presence of ACh-sensitive neurons in the cat''s medulla was demonstrated by means of electrophoretic administration of chemical substances in the immediate vicinity of individual nerve cells using five-barreled micropipette electrodes. Of 819 nerve cells tested, 21.9% increased and 6.7% decreased their rate of activity during ACh administration. Onset and disappearance of change were delayed with respect to duration of ACh tests. Response of ACh sensitive nerve cells to ACh was enhanced by electrophoretic administration of physo-stigmine to the cell and could be blocked by administration of dihydro-[beta]-erythroidine and hexamethonium. Only two of the 34 respiratory nerve cells investigated were ACh sensitive, both were expiratory neurons. Of these, one unit decreased while the other increased its discharge rate during ACh tests.