The effects of β-adrenoceptor blockade on resting heart rate

In the graph below, data for atenolol and placebo are taken from the collated practical classes in 2022, while data for pindolol was obtained from a previous cohort of students.

Figure 1: The effect of β-adrenoceptor antagonists on the resting heart rate of healthy individuals over time. Placebo (vitamin B6, 10 mg), atenolol (50 mg) or pindolol (10 mg) were administered at 0 min. Data shown as mean ± s.e.m. * p<0.05 drug vs placebo (ANOVA); n = 41-73 per treatment. Bpm, beats per minute.

Briefly describe the data shown.