INTRODUCTION: Physiological regulation of GnRH secretion in mammals is associated with complex interplay between excitatory and inhibitory neurotransmitter and neurohormone systems within the hypothalamus that mediate oestrogen signals to GnRH cells. Among numerous studies on the neuroendocrine processes controlling GnRH secretion only a few research have revealed that hypothalamic GnRH acting locally may also participate in the regulation of its own release, but the mechanisms involved remain poorly understood. AIM(S): This study was designed to evaluate the effect of prolonged intermittent infusion of small doses of exogenous GnRH on GnRH and GnRH receptor (GnRHR) biosynthesis in the hypothalamus, GnRHR expression in the anterior pituitary gland (AP), and on LH secretion in sexually inactive sheep. METHOD(S): Studies were conducted on 3–4-year-old Polish Merino ewes during the middle of the anestrous season. Infusions of exogenous GnRH (0.2 µg GnRH per animal daily) were performed into the third cerebral ventricle for 3 consecutive days. The control for GnRH-treated group was animals infused with equivalent to GnRH volume of Ringer’s solution. The measurement of GnRH and GnRHR levels was performed using an enzyme-linked immunosorbent assay (ELISA). Plasma LH concentration was analysed by a double-antibody radioimmunoassay (RIA). RESULTS: The results of this study demonstrate that prolonged infusion of small doses of GnRH into the third cerebral ventricle of anestrous ewes increased drastically GnRH and GnRHR levels in the hypothalamus, but decreased GnRHR expression in the AP and also reduced LH secretion. CONCLUSIONS: The study indicates the existence of ultrashort loop feedback mechanism of GnRH release from the hypothalamus in which hypothalamic GnRHR participate. Decreased expression of GnRH in the AP and diminished LH secretion in GnRH-treated ewes provide indirect evidence for suppressive effect of exogenous GnRH on GnRH release from hypothalamic nerve terminals. FINANCIAL SUPPORT: This work was supported by grant National Science Center Poland No UMO-2012/05/B/ NZ4/02443.