Effects of exogenous neurohormone, gonadotropin (GtH) and dopaminergic drugs on the serum GtH content and ovulatory responsiveness of wild catfish, Silurus asotus (Linnaeus, 1758)

Abstract

Wild female catfish Silurus asotus (Linnaeus, 1758) were injected with domperidone (DOM) alone, [d‐Ala6, Pro9 Net]‐luteinizing hormone‐releasing hormone (LHRH‐A) alone once or twice, LHRH‐A plus DOM once or twice simultaneously at 6‐h intervals, LHRH‐A plus carp pituitary extract (CPE) twice simultaneously at 6‐h intervals and LHRH‐A plus human chorionic gonadotropin (HCG) twice simultaneously 6 h apart respectively. The results indicated that injection of LHRH‐A at a dosage of 0.01–0.02 μg g−1 body weight (BWt) alone induced a low but significant increase in serum gonadotropin (GtH) (P<0.05) and resulted in a very low ovulation rate, while DOM at a dosage of 5 μg g−1 BWt alone did not induce an increase in the serum GtH levels and ovulation; in contrast, LHRH‐A at a dosage of 0.01 μg g−1 BWt plus DOM at a dosage of 5 μg g−1 BWt (termed the Linpe technique) increased the serum GtH (P<0.05) significantly and induced an ovulatory rate of 100%, while LHRH‐A plus CPE or HCG resulted in an increase in the serum GtH (P<0.05) and high ovulatory rate, although the latency period was longer when fish were given LHRH‐A plus HCG or CPE.

Effects of in vivo treatment with the dopamine antagonist pimozide and gonadotropin-releasing hormone agonist (GnRHa) on the reproductive axis of Senegalese sole (Solea senegalensis)

“…For example, treatment of European sea bass with the DA antagonist domperidone, either alone or combined with GnRHa, had no effect on spontaneous or GnRHa-induced OM or spawning (Prat et al, 2001). In contrast, in species expressing a strong DA inhibitory tone, DA antagonists stimulated OM and spawning when given as single treatments, and enhanced GnRHa-induced effects in combined treatments (Yaron, 1995;Wen and Lin, 2004;. The results from the present study indicate that an endogenous DA inhibition would not be the cause for the absence of spontaneous egg release in cultured Senegalese breeders.…”

“…In these species it is required 3 3 the co-administration of GnRHa with DA antagonists, in order to remove the endogenous DA inhibition and permit the stimulatory action of GnRHa on the reproductive axis (Peter and Yu, 1997;Mylonas et al, 2009). Combined treatment of GnRHa with DA antagonists, such as pimozide (PIM) or domperidone, has been used successfully to stimulate reproduction in cyprinids (Yaron, 1995;Mikolajczyk et al, 2004), catfishes (Silverstein et al, 1999;Wen and Lin, 2004) and mullets (Arabaci and Sari, 2004;Aizen et al, 2005). But, only few studies have investigated the DA system in marine fishes, with no conclusive results.…”

Broodstock management and hormonal manipulations of fish reproduction

“…Broodstock management and hormonal manipulations of fish reproduction 29 removes the inhibition on the gonadotrophs and enhances the stimulatory effect of GnRHa on LH release. Currently, hormonal manipulations of reproduction using a combined GnRHa/DA antagonist treatment are used mostly in cyprinids (Kaminski et al, 2004;Mikolajczyk et al, 2003;Mikolajczyk et al, 2004;Yaron, 1995), catfishes (Brzuska, 2001;Silverstein et al, 1999;Wen and Lin, 2004) and mullets (Aizen et al, 2005;Glubokov et al, 1994).…”

“…Similarly, two injections of 20 µg Kg -1 GnRHa with 5 mg Kg -1 of the DA antagonist pimozide induced ovulation in 95% of treated common carp (Mikolajczyk et al, 2004). Two injections of GnRHa in combination with a DA antagonist have been used successfully also in the koi carp (Cyprinus carpio) , lake mullet (Chalcalburnus tarichi) and wild catfish (Silurus asorus) (Wen and Lin, 2004). Finally, a single injection of 20 µg Kg -1…”

Edwardsiella tarda infection in Korean catfish, Silurus asotus, in a Korean fish farm

“…Korean catfish, Silurus asotus , is broadly distributed throughout the freshwater of Korea, China and Japan (Wen & Lin 2004), and represents one species of commercially valuable fish in Korea. Since early times, catfish has been widely utilized as a nutritive food and a folk medicine (Park, Im, Jeong & Kim 2002).…”