Methyllycaconitine

Methyllycaconitine (MLA) is a plant alkaloid found in the larkspur, and has been identified as an antagonist of nicotinic acetylcholine receptors (nAChrs) in the muscle and brain. It is one of many alkaloids found in the larkspur, but is believed to be one of the major culprets in the poisoning of livestock in the Western United States.

Toxicology
Larkspur poisoning in cattle results in labored breathing, rapid and irregular heartbeat, muscular weakness, and collapse. This is believed to be a result of the blockade of nAChrs in the neuromuscular junction, and of antagonism of the &alpha;7 nAChrs in the brain.