In addition to steroid hormones the maturating follicles in ewes produce oxytocin (OXT) which exerts, by local and central effects, the influence on folliculogenesis. Several previous studies have revealed that short-term treatment with OXT in such species as rats and cattle stimulates gonadotropin secretion. Furthermore, it has been indicated that OXT can reduce estrogen production. Both of these effects can favour the ovulation rate (OR). The goal of this study was to reveal the effect of prolonged injections of the OXT (0,1 I.U. every 30 min per 12 h, i.m. and i.v.) on the ovulation rate and contents of leptin and estradiol (E₂) during the oestrus in ewes. Within 2 h of OXT administration both i.m. and i.v., the level of leptin started to increase but E₂ at the same time decreased. More pronounced differences were observed when OXT was given intravenously. Under the influence of OXT given i.m. or i.v. the ovulation rate rose by up to 0,15 and 0,30 ova per ewe respectively. These results are consistent with the assumption that OXT may modulate the selection of premature follicles in the last phase before ovulation.

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