Agents known to alter synthesis, storage, release, reuptake or catabolism of the monoamines (Lippmann, 1968; Rubinstein & Sawyer, 1970), and excess amounts of 5-hydroxytryptamine (5-HT), can both interfere with ovulation and ovarian development (Brown, 1967; Vaughan, Benson & Norris, 1970). Conversely, manipulation of sex steroid levels alters hypothalamic catecholamine content (Lichtensteiger, Korpela, Langemann & Keller, 1969), and cyclic variations in hypothalamic catecholamines (Lichtensteiger, 1969) and monoamine oxidase activity have been observed during the oestrous cycle (Zolovick, Pearse, Boehlke & Eleftheriou, 1966).
Whether one monoaminergic system alone regulates gonadotrophin secretion or whether secretion is dependent upon a more complex integrative mechanism, as suggested by Lippmann (1968), remains to be determined. In most investigations, one or a combination of several pharmacological agents have been employed to alter brain levels of the various monoamines. However, these agents do not permit the selective manipulation of only one monoaminergic system without affecting others. Recently, intracisternal