Does Prolactin Modify Testosterone Feedback in the Hamster? Pituitary Grafts Alter the Ability of Testosterone to Suppress Luteinizing Hormone and Follicle-Stimulating Hormone Release in Castrated Male Hamsters*

Adult male golden hamsters maintained in a long photoperiod (14 h of light and 10 h of darkness) or in a short photoperiod (5 h of light and 19 h of darkness for 7 weeks) were castrated and either given one anterior pituitary transplant under the kidney capsule or sham-operated. Additional animals were castrated and grafted or sham-grafted at the time of transfer to the short photoperiod. Starting 2 weeks after castration, all animals were injected three times a week with 20 μg testosterone propionate (TP). After 3 weeks, the dose of TP was increased to 80 jig and, after an additional 2 weeks, to 320 μg per injection. Blood samples were collected 2 weeks after castration and 1 day after the last injection of 20, 80, and 320 μg TP. Short photoperiod reduced and pituitary grafts increased plasma PRL levels. Plasma testosterone levels were related to the dose of injected TP, but were not influenced by photoperiod or pituitary transplants. Before the onset of TP injections, plasma LH and FSH levels in grafted...