Journal of Neuroscience, Vol 10, 3646-3652, Copyright © 1990 by Society for Neuroscience
Serotonin synthesis and distribution in Drosophila dopa decarboxylase genetic mosaics
AM Valles and K White
Department of Biology, Brandeis University, Waltham, Massachusetts 02254.
In Drosophila, the enzyme dopa decarboxylase (DDC) catalyzes the last step
in the biosynthesis of serotonin (5HT) and dopamine. In the present study,
the distribution of DDC and one of its biosynthetic products (5HT) was
determined in CNSs that were genetic mosaics, composed of neurons that have
DDC activity and neurons that lack DDC activity. Phenotypic mosaicism, that
is, immunoreactive (IR) and non-IR neurons within the same nervous system,
was observed for both DDC and 5HT immunoreactivity. DDC-IR neurons were
always 5HT-IR, but some 5HT- IR neurons devoid of DDC immunoreactivity were
also observed. 5HT-IR neurons devoid of DDC immunoreactivity were always in
close apposition to other DDC-IR neurons. We suggest that in vivo uptake
mechanisms are responsible for 5HT accumulation in neurons devoid of DDC
immunoreactivity.