nicotinic Definition

relating to, resembling, producing, or mediating the effects produced by nicotine on nerve fibers at autonomic ganglia and at the neuromuscular junctions of voluntary muscle which increases activity in small doses and inhibits it in larger doses

niacin

an acid C6H5NO2 of the vitamin B complex found widely in animals and plants and used especially against pellagra; also : nicotinamide —called also nicotinic acid