Leuphasyl® is a pentapeptide (also known as Pentapeptide-18 with sequence Tyr-D-Ala-Gly-Phe-Leu) that modulates Ca2+ channels in vitro. It is an enkephalin-like peptide that has proven effective in reducing expression wrinkles with an alternative mechanism to Botulinum toxin-like molecules. Natural enkephalins are endogenous opioids: they inhibit neuronal activity. Their receptors are outside neurons, coupled to G proteins of the inhibiting type (Gi). The docking of enkephalin molecules in these receptors results in the release of the G protein subunits (alpha, beta, gamma) within the cell.
These subunits close Ca2+ channels and open K+ channels. Preventing the entry of Ca2+ into the neuron avoids vesicle fusion and consequently inhibits acetylcholine release across the synapse to the muscle.
Pentapeptide-18 acts similar to natural enkephalins (proven in vitro study): it couples to the enkephalin receptor on the outside of the nerve cells. When Leuphasyl® couples to the receptor, a conformational change initiates a cascade inside the neuron that decreases its excitability: nerve cell activity is "turned down," and the release of acetylcholine modulated. As a result, muscle contraction will be relaxed, and therefore, expression wrinkles will be diminished.