[A reminder of the structure and function of the skeletal neuromuscular junction]

The skeletal neuromuscular junction has been considered as a model of chemical synapses due to its relatively simple organization. It is made up of three cellular partners including the motoneuron nerve terminals, the peri-synaptic Schwann cells and a specialized region of skeletal muscle fibers. It has been extensively studied revealing its ultrastructural complexity involving many molecular actors. The neuromuscular junction is a highly specialized structure, optimized for the rapid transmission of information from the presynaptic nerve terminal to the post-synaptic muscle fiber. This rapid transmission requires a very close apposition of plasmic membranes of pre- and post-synaptic partners, and a strict structural and molecular arrangement on both sides of the narrow synaptic cleft separating nerve terminal and muscle membranes. In this short review, we summarize the knowledge regarding pre- and post-synaptic ultrastructural specializations and give an overview of some functional aspects of neuromuscular transmission, including the quantal acetylcholine release process, which will help to better understand the pharmacological actions of botulinum toxins in esthetic and corrective dermatology.