Dopamine and senescence in Drosophila melanogaster.

Five-day-old Drosophila melanogaster males, when exposed to 2-h-old males, will perform courtship rituals; the intensity and duration of this behavior rapidly diminishes with time. The ability of the older males to habituate to the attractive signals given off by the younger males is a dopaminergic-modulated experience-dependent modification of behavior that is abolished with increasing age. Dopamine-depleted females show increased resistance to copulation; 20-day-old females demonstrated an increase in copulation avoidance compared with younger (5-15-day-old) females. These changes in dopaminergic-modulated behaviors observed during aging parallel declines in whole body levels of dopamine. Immunocytochemical analysis of adult brains using an antibody raised against Drosophila tyrosine hydroxylase to visualize catecholaminergic cell bodies revealed increased degeneration of the cell bodies with aging. These results suggest that the deficits seen in dopaminergic-modulated behaviors may arise as a consequence of degenerative changes within the aging brain.