The document summarizes various models used to screen neuromuscular blocking agents. Intact unanesthetized animal models include testing contractures in birds, righting reflex in rats and mice, and inclined screen and inverted grid methods using mice or rats. Anesthetized animal models include nerve-muscle preparations of limbs and phrenic nerve-diaphragm preparations. In vitro studies involve isolated nerve-muscle preparations like frog nerve-muscle and phrenic nerve-diaphragm, as well as lumbrical nerve-muscle preparation in rabbits and electrical activity of single muscle fibers. These models are used to classify and determine potency of depolarization versus non-depolarization blocking agents