24-h changes in plasma prolactin levels in female lactating rabbits. Groups of 6–7 animals maintained with their litters or separated from them for 48 h were killed by decapitation on day 11 post-partum, at 6 different time points throughout a 24-h cycle, starting at 0900 h. The dark bar indicates scotophase duration. Results are the means ± SEM. Letters indicate the existence of significant differences between time points in each group after a one-way ANOVA followed by a Student-Newman-Keuls' test, as follows: ap < 0.05 vs. 09:00 and 17:00 h, bp < 0.01 vs. 09:00 h, p < 0.05 vs 05:00 h. For further statistical analysis, see text.
Cano et al. Journal of Circadian Rhythms 2005 3:9 doi:10.1186/1740-3391-3-9