LUTEINIZING AND FOLLICLE-STIMULATING-HORMONE SECRETION DURING MEDIAN-EMINENCE PERFUSION OR INTRAVENOUS-INFUSION WITH GONADOTROPIN-RELEASING-HORMONE ANTISERA IN OVARIECTOMIZED EWES

Effects of passive immunization against gonadotrophin-releasing hormon e (GnRH) on luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion were examined in six ovariectomized (OVX) ewes during the breeding season (8L:16D). The same amount of rabbit anti-GnRH seru m was administered by intravenous infusion or median eminence (ME) per fusion over 30 h. Administration of anti-GnRH serum by both routes fai led to affect FSH (P>0.05) but equally reduced basal and mean circulat ing LH concentrations and LH pulse amplitude (P<0.05). Luteinizing hor mone pulse amplitude was also reduced by ME perfusion with vehicle (P< 0.05). Luteinizing hormone interpulse interval was not affected by int ravenous infusion with anti-GnRH serum but was increased by ME perfusi on with anti-GnRH serum (P<0.05). The results suggested that targeting the ME of the ovariectomized ewe with perfusion of GnRH antiserum for 30 h blocked pulsatile LH secretion, leaving only basal secretion, an d had no effect on FSH secretion.