Effect of gonadotropin-releasing
hormone analogue (GnRHa) and pimozide on plasma levels of sex steroids and
ovarian development in sea bass (Dicentrarchus labrax L.)
F.
Prat, S. Zanuy, M. Carrillo-2001
Aquaculture, 198 (3-4): 325-338
Abstract:
To synchronise and advance spawning, European sea
bass females in late vitellogenesis were treated with two i.p. injections of
GnRH analogue alone (5 and 20 µg/kg BW) given 12 h apart, or combined with
pimozide (PIM) (10 mg/kg BW) either in the first or second injection.
Saline-injected and untreated females were used as controls. Administration
of GnRHa alone or combined with PIM accelerated the final oocyte maturation
(FOM) and induced spawning. However, 48 h after the second injection the
size of oocytes and the percentage of oocytes in GVBD stage were lower in
the PIM-treated females. The number of eggs spawned was highest in the group
that received GnRHa alone and lowest in the group that received PIM in the
second injection. Plasma levels of 17 β-oestradiol (E2) increased
sharply at 12 h after the first injection of GnRHa alone or combined with
PIM, decreasing after a second injection of GnRHa alone. However, the plasma
E2 decreases was much slower in females that received the PIM in the first
injection. Females that received PIM in the second injection still showed
elevated plasma E2 during a longer period. Plasma testosterone (T) increase
was parallel to the plasma E2 decrease and peaked earlier in the group that
received GnRHa alone in both injections. Low and nonsignificant changes of
17 α,20 β -dihydroxy-4-pregen-3-one (17,20 β -P) were
observed in plasma during the time that the animals were sampled. The
results demonstrate that the use of PIM does not improve the GnRHa treatment
and the use of GnRHa alone during the last stages of vitellogenesis is
enough to induce FOM in the European sea bass.
(Department of Reproductive Fish Physiology,
Instituto de Acuicultura de Torre de la Sal, C.S.I.C. Ribera de Cabanes,
12595 Torre de la Sal, Castellón, Spain, Tel.: +34-964-319-500; fax:
+34-964-319-509, e-mail:of M. Carrillo: carrillo@iats.csic.es