Diurnal variation in nicotine sensitivity in mice: Role of genetic background and melatonin

► Nicotine sensitivity is time of day dependent in melatonin proficient C3H/Ibg mice. ► Melatonin deficient strains do not exhibit daily variations in nicotine sensitivity. ► Hypothalamic α-bungarotoxin binding sites exhibit daily variations in expression. ► Daily variations in nicotine sensitivity are in part melatonin signaling dependent.