**2.6. Melatonin administrations**

First, melatonin was dissolved in 100% ethanol (1/10 μl) and then diluted in saline (0.9 % NaCl) (9/10 μl) to the desired concentrations. Stock solutions were kept at 4 °C prior to use. The stock was diluted with sterile saline to the desired concentrations in order to make fresh working melatonin solutions. Vehicle solutions were made in the ratio of one part absolute ethanol to 1000 parts sterile saline. Melatonin was injected in a dose of either 1 or 100 μg/kg (15:00 pm).
