en Biology & physiology Biology & physiology پژوهشي Orginal research papers The effectiveness of two kinds of dopamine antagonist (DA), metoclopramide (Met) and domperidone (Dom) combined with the gonadotropin releasing hormone analogue (D-Ala⁶, Des Gly¹⁰ ethylamide) GnRHa was assayed on the ovulation success, latency period, ovulation index (OI) and fertilization success of kutum, <em>Rutilus frisii kutum</em> (Kamenskii, 1901). Brood fish were injected intra-peritoneally as follows: 2 mg/kg b.w. of carp pituitary extract (CPE) as a control, 5 g+ 2.5mg, 1mg+ 5mg and 2mg+ 10mg/kg b.w. of GnRHa + Met or Dom in a single injection.<br> Based on the ovulation and fertilization success, no significant differences between similar doses of Dom and Met when combined with similar doses of GnRHa were found (p>0.05). However, in some groups, the OI and latency period were greater when Dom was used as a DA instead of Met (p<0.05). In general, the results of this study showed that the potency of Dom was nearly same as Met when combined with GnRHa and used as a DA in kutum. It is strongly recommended to repeat the experiment under different conditions to find out definite conclusion. Kutum, Rutilus frisii kutum, Spawning, GnRHa, metoclopramide, domperidone 105 118 http://jifro.ir/browse.php?a_code=A-10-600-114&slc_lang=en&sid=1 F. Peykan Heyrati 100319475328460024278 100319475328460024278 No S. Dorafshan dorafshan@modares.ac.ir 100319475328460024279 100319475328460024279 Yes