Nutrition and dopamine: An intake of tyrosine in royal jelly can affect the brain levels of dopamine in male honeybees (Apis mellifera L.).

Precursors of neuroactive substances can be obtained from dietary sources, which can affect the resulting production of such substances in the brain. In social species, an intake of the precursor in food could be controlled by social interactions. To test the effects of dietary tyrosine on the brain dopamine levels in social insect colonies, male and worker honeybees were fed tyrosine or royal jelly under experimental conditions and the brain levels of dopamine and its metabolite were then measured. The results showed that the levels of dopamine and its metabolite in the brains of 4- and 8-day-old workers and 8-day-old males were significantly higher in tyrosine-fed bees than in control bees, but the levels in 4-day-old males were not. The brain levels of dopamine and its metabolite in 4- and 8-day-old males and workers were significantly higher in royal jelly-fed bees than in control bees, except for one group of 4-day-old workers. Food exchanges with workers were observed in males during 1-3 days, but self-feedings were also during 5-7 days. These results suggest that the brain levels of dopamine in males can be controlled by an intake of tyrosine in food via exchanging food with nestmates and by self-feeding.