One hundred flies were allowed to age for 3 to 5 days on standard cornmeal/yeast/molasses-agar culture medium before being fed a 4% sucrose solution supplemented with 1ug/uL cocaine for at most 2 hours. Brains from the first 40 flies that consumed 0.53uL of the sucrose/cocaine solution were then dissociated with collagenase and stepwise trituration.