Hypothalamic control of prolactin release in the rainbow trout,Salmo gairdneri: in vitro studies

Francis Gonnet (1) , Alain Barret (2) , Dominique Grouselle (2) , Patrick Prunet (1)

1 Laboratoire de physiologie des poissons
2 INSERM U36 - Pathologie vasculaire et endocrinologie rénale - Chaire de médecine expérimentale

Hypothalamic control of prolactin (PRL) release in immature rainbow trout Salmo gairdneri was investigated using an in vitro perifusion system of the rostral pars distalis. Hypothalamic extract of trout induced a dose dependent stimulation of PRL release. A similar effect was observed when infusing the medium from a 24h static incubation of the hypothalamus. Extracts from different control tissues (muscle, liver, gut) did not change in vitro release, thus confirming the specificity of this stimulatory effect. Hypothalamic extract from adult male rat, known to contain PRL release inhibiting factors, stimulated in vitro PRL secretion in rainbow trout. This suggests that PRL cells are predominantly influenced by PRL releasing factors. Measurement of TRH and serotonin content in trout hypothalamus indicated consistent physiological levels of these two factors. HPLC studies of hypothalamic extract showed that immunoreactive - TRH eluted at the same place as labelled TRH standard. Moreover, pizotifen, a serotonin antagonist, partially inhibited the stimulation observed with trout hypothalamic extract. These results suggest that, in immature rainbow trout, PRL release is under stimulatory hypothalamic control and that serotonin and probably TRH play a major role in this control.

Mots clés: fish; rainbow trout; prolactin; perifusion; pituitary; hypothalamus

Domaines: Sciences du Vivant [q-bio]

Francis Gonnet, Alain Barret, Dominique Grouselle, Patrick Prunet. Hypothalamic control of prolactin release in the rainbow trout,Salmo gairdneri: in vitro studies. Fish Physiology and Biochemistry, 1989, 7 (1-6), pp.301-308. ⟨10.1007/BF00004721⟩. ⟨hal-02728192⟩