Corticosteroid and neurohypophyseal hormone control of parturition in the guppy,Poecilia reticulata

Both increased day length and immersion in distilled water elicited parturition in the pregnant guppy, Poecilia reticulata. Injections of deoxycortisol, oxytocin, vasotocin, and an extract of carp neurohypophyses also induced premature parturition. In vitro, deoxycortisol promoted the breakdown of follicular membranes, thus expediting explusion of young by contractions of ovarian smooth muscle induced by neurohypophyseal hormones.