Early development of the serotonergic and dopaminergic nervous system in Spisula solidissima (surf clam) larvae

We have defined the development of the serotonergic and dopaminergic compon ents of the central nervous system in the early Spisula solidissima (surf c lam) embryo using HPLC and immunocytochemistry. HPLC analysis reveals norep inephrine, dopamine, and serotonin are present at 24 h post-fertilization. Immunocytochemistry shows that the serotonergic nervous system emerges duri ng the late trochophore stage with the development of a single serotonergic cell, C/A1, in the cerebral/apical ganglion. After 48 h, a second serotone rgic cell forms, C/A2, which is connected to C/A1 by two serotonergic proce sses, and a single serotonergic cell emerges in the visceral ganglion, V1. At 72 h, a new serotonergic cell body develops in the cerebral/apical gangl ion, C/A3. After 96 h, the cerebral/apical ganglion and visceral ganglion a re connected by a serotonergic process. Expression of the dopamine receptor , D-2, begins by 24 h with a generalized expression in the region of the de veloping gut. D-2 expression in the gut ceases by 48 h. At 48 h, a network of fibers forms dorsolateral to the mouth. By 72 h, D-2 expressing projecti ons emerge from this network. (C) 2001 Elsevier Science Inc. Ail rights res erved.