Effect of melatonin on 5 Gy γ-radiation-induced caspase-3 activity in the splenocytes of Funambulus pennanti. Animals were sacrificed after 4 h exposure during (a) the reproductively active phase (RAP) and (b) the reproductively inactive phase (RIP). (c) A comparison of caspase-3 activity between RAP and RIP irradiated (I) and RAP and RIP melatonin-treated plus irradiated (MI) groups, in which controls of both phases were assumed to be 100%. Vertical bars represent mean±SEM (standard error of the mean), n _ 5 for each group. The statistical significance is indicated: a _ p<0.05, b _ p<0.01 when compared with the control group; d _ p<0.01 when compared with the irradiated group. Con, control; Mel, melatonin only; Irrd, irradiation only; Mel+Irrd, melatonin treatment and irradiation.