Blood pressure elevation in rats by peripheral administration of Tyr-Gly-Gly-Phe-Met-Arg-Phe and the invertebrate neuropeptide, Phe-Met-Arg-Phe-NH2.

Phe-Met-Arg-Phe-NH2 (FMRFamide), injected at less than 1 mumol/kg intravenously in the anesthetized rat, produces sharp elevations of blood pressure and changes in respiration. The effects were dependent on the carboxyterminal Arg-Phe (RF) configuration and were stereospecific for these two amino acids. A related peptide with RF carboxyterminus, gamma 1-melanotropic stimulating hormone, also had potent blood pressure stimulating activity. The mechanisms underlying the pressor effect of FMRFamide have not yet been established but this pressor action was not significantly attenuated by standard pharmacologic antagonists or prevented by removal of the adrenal or pituitary gland.