Nicotinic receptors at the neuromuscular junction are arranged in a rosette pattern (Fig 1).

Every receptor consists of five subunits. There are two alpha (α) subunits, each with a molecular weight of 40 000 Da. Each of these has a single acetylcholine binding region. Activation of the receptor requires both α sites to be occupied. The other three subunits are beta (β), delta (δ) and epsilon (ε), which are slightly larger.

In fetal muscle, the epsilon is replaced by a gamma (γ) subunit.

A molecule of ACh needs to slot into each of the receptor sites in the α subunits for the receptor to be activated. The channel then opens, allowing many Na⁺ ions to enter the post-synaptic cell and a few K⁺ ions to leave it, thus depolarizing it.