[en] The present work was carried out at rabbit colony established in Endocrinology Research Unit, Applied Radiobiology Department, Nuclear Research Center, Atomic Energy Authority, Inshas, Egypt. The hormonal radioimmunological assays were performed in the laboratories of the same Research Unit. It was planned to point out the effect of treating adult does subjected to three regimes of photoperiodicity 8 hrs D/16 hrs L, 12 hrs D/12 hrs L and 16 hrs D/8 hrs L , with different hormonal treatments including HCG and pharmaceutical preparations including Melatonin, Serotonin, Bromocriptine (anti prolactin), Indomethacin (anti prostaglandins) alone or in combined with HCG. A total number of 300 young adult female New Zealand white does aged 3-4 months and weighed 2-3 Kg were individually caged and kept in an environmental chamber under 0 controlled ambient temperature of 25 degree C, isolated from outdoors day light and well ventilated This work was accomplished in two separate experiments spaced with two weeks rest to adapt the animals for the photoperiod regime, does subjected to study were kept under these condition for pre-experimental period leaved two weeks then divided into three groups (photoperiods) each of 100 does. The first experiment: was planned and conducted to detect the possibility for improving the reproductive performance of does by magnifying the hormonal coordination related to productive activity with relation to different lighting regimes tested, to fulfill this aim applying human chorionic gonadotropin as well as other chemical compounds that thought to have considerable effect on hormonal regulation of reproduction (Melatonin, Serotonin, Bromocriptine (anti prolactin) and indomethacin (anti prostaglandin)).