The effects of GnRHa with and without dopamine antagonist on reproductive hormone levels and ovum viability in tench Tinca tinca

Abstract The study evaluated the impact of mGnRHa ([D-Tle 6 , Pro 9 , NEt]-mGnRH), with or without metoclopramide, on release of luteinizing hormone (LH) and sex steroids and on viability of ova in tench Tinca tinca . Four experimental groups were subjected to the following treatments given as intraperitoneal injection: 0.9% NaCl (C); 25 μg kg − 1 mGnRHa (Gn); 25 μg kg − 1 mGnRHa with 20 mg kg − 1 metoclopramide (GnM); and or 20 mg kg − 1 metoclopramide (M). GnM treatment induced LH surge reaching maximum concentrations 6 h post-treatment followed by a slight but significant decline ( P P 2 ) or testosterone blood level. Significant decrease from baseline ( P 2 values at the end of trial period in both Gn and GnM. Testosterone values increased with Gn and the GnM, peaking 12 h post-treatment and dropping to baseline levels at 24 h. GnM was associated with significant increase of 17α, 20β-dihydroxy-4-pregnen-3-one (17,20 β -P) values at 6 h ( P P β -P secretion, possibly the source of the adverse effects on ovum viability. We describe for the first time the negative impact of metoclopramide combined with mGnRHa hormone treatment on ovum quality in tench. Statement of relevance Improvement of fish artificial reproduction.