This experiment tested whether F344 rats have the capacity for stronger responses to SD than that induced by SD alone. At age 3 days, 20 male F344 rats gestated and born in LD (16L:8D; lights-on at 0500 h) received s.c. injections of 1 mg of TP in 0.1 ml of corn oil. The dose was chosen because, in a pilot study, this dose inhibited reproductive development in SD but not LD. Twenty control rats received injections of oil vehicle alone. Rats were kept in LD until aged 21 ± 2 days, when both the TP and control groups were divided into weight-matched halves, with one half of each group placed into a second room in SD (8L: 16D; lights-on at 0900 h) or kept in LD (n = 10 rats/group in the four treatments). The experiment was run in three replicates balanced across treatments; the data from the three replicates were combined for the analyses. ventolin inhalers
Rats were housed individually in polypropylene cages (36 X 24 X 19 cm) and provided with food (RMH 3000; Southern States Cooperative; Williamsburg, VA) and tap water ad libidum (ad lib). Temperature was 23 ± 2°C, and relative humidity was between 30% and 70%. Experiments were conducted in accordance with the Guiding Principles for the Care and Use of Research Animals promulgated by the Society for the Study of Reproduction.