Pharmacological Actions of Hemlock (Conium Maculatum) Alkaloids

The actions of three hemlock alkaloids—coniine, N-methylconiine and α-coniceine—have been examined on isolated tissues, on anaesthetised cats and hens and on conscious mice and young chicks. The most pronounced action of the alkaloids was to block spinal reflexes by an action exerted in the spinal cord. Their peripheral actions on autonomically innervated structures were mainly a consequence of an initial stimulant and a secondary depressant action on autonomic ganglia. Large doses of the alkaloids stimulated skeletal muscle and subsequently caused neuromuscular block. This blocking action differed in many respects from that produced by decamethonium or tubocurarine.