Prostaglandin F (2-alpha) is involved in a number of physiologic processes. It serves as a potent luteolytic agent in many species, has been implicated as a modulator of intraocular pressure, smooth muscle contraction in the uterus and elsewhere. Its effects on cells are mediated through specific interaction with the prostaglandin F receptor (FP or PTGFR). Knockout mice lacking the FP receptor are unable to deliver normal fetuses at term due to a lack of response to oxytocin. The mice also failed to show the decline in serum progesterone expected to precede parturition.