The effects of medicinal plants on muscarinic receptors in various types of smooth muscle.

Pharmacological agents that can affect muscarinic receptors are commonly used to treat or manage various diseases. Medicinal plants have been used from ancient time to treat cardiovascular, gastrointestinal, respiratory, and urogenital disorders, which may related to their muscarinic receptors effects. Several pharmacological studies revealed the inhibitory or stimulatory effect of some herbal plants on muscarinic receptors. Medline, PubMed, Science Direct, Scopus, and Google Scholar as online database were searched from the beginning of 1983 to March 2018 using following keywords: muscarinic receptor, medicinal plant, herbal medicine, and smooth muscle, animal, human, in vivo, and in vitro. The original studies in English language were included. Based on the results of the reviewed articles, more than 70 medicinal plants extracts or constituents affected muscarinic receptors (stimulatory or inhibitory) of smooth muscles in cardiovascular, gastrointestinal, respiratory, and urogenital systems. Among them, there are some tropical plant and herbs that have been traditionally used as food additive. The therapeutic properties of these plants may be regarded in treatment of cardiovascular (hypertension and tachycardia); gastrointestinal (diarrhea, colitis, and constipation); and urological (overactive bladder, abortion, and preterm labor) diseases. However, more clinical trials are needed to use some of these medicinal plants in clinical target therapy.