Nicotine injected intravenously or on pituitary in vivo stimulated maturational gonadotropin (GtH2) secretion in domperidone (D-2 receptor antagonist) pretreated carps. The effective dose was 1 mg·kg−1 and 100 μg·kg−1, respectively. No stimulatory effects of nicotine were observed in normal (non-treated) carps. When nicotine was injected together with gonadotropin releasing hormone (GnRH) analogs (D-Arg6 sGnRH or D-Ala6 LHRH) a clear potentiation effect of nicotine on GnRH analogs' action was observed. This potentiation was seen even in normal fish where nicotine itself had no effect on GtH2 release. A synergism between nicotine and GnRH analogs appeared when low doses of GnRH analogs were used. In domperidone pretreated fish, this synergism occurred after injection of 1 μg·kg−1 of sGnRHa. In normal fish, the same phenomenon was observed after injection of 5 μg·kg−1 of sGnRHa or 20 μg·kg−1 of LHRHa. Higher doses of GnRH analogs mask this effect. Results confirm previous in vitro findings on the stimulatory action of nicotine on GtH2 secretion. They also indicate a possible synergy between nicotine and GnRH as well as an inhibitory influence of dopamine on nicotine's action.

F1 hybrids were produced by crossing, in artificial conditions, female Barbus barbus and male B. meridionalis. Results from the genetic study describing enzymatic patterns produced after electrophoresis of experimental F1 hybrids confirmed a great part of the original interpretation of patterns observed in the natural population. Morphological studies which examined denticle length on the last hard ray of the dorsal fin (well developed in B. barbus and absent in B. meridionalis), showed that F1 hybrids' values were not exactly intermediate between the parental values. Up to two years old, experimental hybrids displayed identical growth rates and sexual dimorphism of length (in favour of the females) as B. barbus growing in the same conditions. At this age, in female hybrids, the ovaries matured and produced fertilizable ovules: in male hybrids, the testicles were morphologically normal but no sperm was produced. If this sterility is confirmed in the reciprocal cross (male B. barbus × female B. meridionalis), the phenomenon would be an essential feature in understanding this hybridization.