Developmental changes in expression patterns of two dopamine receptor genes in mushroom bodies of the honeybee, Apis mellifera

The expression patterns of two dopamine receptor genes, Amdop1 and Amdop2, in the developing mushroom bodies of the honeybee brain were determined by using in situ hybridisation. Both genes were expressed throughout pupal development, but their patterns of expression in the three major divisions of mushroom body intrinsic neurons (outer compact cells, noncompact cells, and inner compact cells) were quite distinct. Amdop1 expression could be detected in all three mushroom body cell groups throughout development. Staining for Amdop1 mRNA was particularly intense in newly born Kenyon cells, suggesting that levels of Amdop1 expression are higher in newborn cells than in more mature mushroom body neurons. This was not the case for Amdop2. Amdop2 expression in the mushroom bodies was restricted to inner and outer compact cells during most of pupal development, appearing in noncompact cells only late in metamorphosis or at adult eclosion. In contrast to the case with Amdop1, staining for Amdop2 mRNA was observed in glial cells. Expression of Amdop2 in glial cells was detected only at early stages of glial cell development, when the cells are reported to be actively dividing. This study not only implicates dopamine in the development of honeybee mushroom bodies but also suggests different roles for the two dopamine receptors investigated.