Unresponsiveness of the reproductive organs of the male mouse to treatment with a potent luteinizing hormone-releasing hormone agonist (ICI-118,630).

The effects of administration of a luteinizing hormone-releasing hormone (LHRH) analogue (ICI-118,630) on plasma concentrations of hormones and weights of reproductive organs were studied in male mice. A single injection of the analogue (54 micrograms/kg body weight) caused a transient elevation of the concentration of LH in the plasma, up to 7 times the level in control mice. Daily administration of the analogue for a period of 3 weeks caused a small but significant decrease of the weight of the ventral prostate. The weight of the seminal vesicles in mice treated with the analogue, however, did not differ from that in control animals. The concentration of testosterone and LH in the plasma of these mice was not significantly different from those in control mice. It is demonstrated that the LHRH-analogue has no "castration-like" effect on the accessory sex organs of the male mouse, which is therefore not a suitable model in the study of these compounds.