Nicotinic receptors are of two types: Nm and Nn. Nm is located in the neuromuscular junction which causes the contraction of skeletal muscles by way of end-plate potential (EPPs).Nn causes depolarization in autonomic ganglia resulting in post ganglionic impulse.m is located in the neuromuscular junction which causes the contraction of skeletal muscles by way of end-plate potential (EPPs). Nn causes depolarization in autonomic ganglia resulting in post ganglionic impulse.