[Ac-D-NAL(2)1,4FD-Phe2,D-Trp3,D-Arg6]-LHRH, a potent antagonist of LHRH, produces transient edema and behavioral changes in rats.

Acute toxicity studies of [Ac-D-NAL(2)1,4FD-Phe2,D-Trp3,D-Arg6]-LHRH (LHRH-A), a potent antagonist of LHRH were performed. Subcutaneous administration of this peptide to rats induced transient edema of the face and extremities. This effect was maximal 3-5 h after peptide administration and subsided by 24 h. These effects were not seen with an LHRH agonist or two other antagonists. This side effects of LHRH-A was peculiar to rats and not observed in mice, rabbits and rhesus monkeys. Intravenous administration led within minutes to depression of spontaneous activity in rats and monkeys. We conclude that some LHRH antagonists produce species specific effects on vascular permeability and spontaneous activity.