Numerous synthetic and highly active forms of GnRH
have been developed principally for clinical use in human
and veterinary medicine, and some long-acting formulation
have been used in some fish species. We considered
des-Gly-His-(Bzl)-GnRH-ethylamide and des-Gly10, DAla6,
Pro-GnRH the most promising because they have
been shown to be biologically active in frogs ([12,18,38-
40]. Similarly, among the numerous DA antagonists on
the market, pimozide has been used successfully in fish
[41] and metaclopromide is active in R. temporaria [32].
Preliminary experiments on a limited number of animals
(Lithobates pipiens and Ceratophrys ornata, data not
shown) and doses reported in the literature were used to
establish the compounds and doses used.