primarily G proteins containing the Gq alpha subunit bound to of the Gq-Gβγ complex(i.e. Gqβγ). Gqβγ then dissociate into its Gq and Gβγ components which act to regulate cell signaling pathways. In particular, Gq stimulates cell signal pathways involving a) phospholipase C/IP3/cell Ca2+ mobilization/diacylglycerol/protein kinase Cs; calmodulin-modulated myosin light chain kinase; RAF/MEK/Mitogen-activated protein kinases; PKC/Ca2+/Calcineurin/Nuclear factor of activated T-cells; and the EGF cellular receptor. In certain cells, activation of FP also stimulates G12/G13-Gβγ G proteins to activate the Rho family of GTPases signaling proteins and Gi-Gβγ G proteins to activateRaf/MEK/mitogen-activated kinase pathways. Functions Studies using animals genetically engineered to lack FP and examining the actions of EP4 receptor agonists in animals as well as animal and human tissues indicate that this receptor serves various functions. It has been regarded as the most successful therapeutic target among the 9 prostanoid receptors. Eye Animal and human studies have found that the stimulation of FP receptors located on Ciliary muscle and trabecular meshwork cells of the eye widens the drainage channels (termed the uveoscleral pathway) that they form. This increases the outflow of aqueous humor from the anterior chamber of the eye through Schlemm's canal to outside of the eyeball. The increase in aqueous humor outflow triggered by FP receptor activation reduces Intraocular pressure and underlies the widespread usage of FP receptor agonists to treat glaucoma. László Z. Bitó is credited with making critical studies to define this intraocular pressure-relieving pathway. Three FP receptor agonists are approved for clinical use in the USA viz., travoprost, latanoprost, and bimatoprost, and two additional agonists are prescribed in Europe and Asia viz., unoprostone and tafluprost. Hair growth Since FP receptors are expresses in human dermal papillae and the use of FP agonists to treat glaucoma has as a side-effect an increase in eyelash growth, it has been suggested that FP agonists may be useful for treating baldness. This is supported by studies in the stump-tailed Macaque primate model of androgen-induced scalp alopecia which have found that the FP agonist, latanoprost, promotes scalp hair growth. These studies have not yet been translated into baldness therapy in humans. Reproduction FP receptor activation contributes to the regression of the corpus luteum and thereby the estrus cycle in many species of farm animals. However, it does not make these contributions in mice and its contribution to these functions in humans is controversial. The receptor has been in use as a