Abstract
Dopamine and histamine are neuromodulators found in the adult stomatogastric nervous system (STNS) of several crustacean species. We used antibodies against tyrosine hydroxylase (TH) and histamine to map the distribution and developmental acquisition of the dopamine and histamine neurons in the STNS of the lobster, Homarus americanus. Embryos, larvae, juvenile and adult animals were studied. TH labeling was present in the STNS as early as E80-85 (80-85% of embryonic development). A subset of preparations in embryos, larvae, juveniles, and adults contained 1-5 labeled somata in the stomatogastric ganglion. Histamine staining appeared in the STNS as early as E50. The distribution of both TH and histamine staining remained relatively constant through development. Electrophysiological recordings demonstrated that receptors for both amines are present in the embryo. Bath application of dopamine increased the frequency of the pyloric rhythm in embryos, and evidence for dopaminergic activation of peripherally initiated spiking in motor axons was seen. In embryos and adults, histamine inhibited the motor patterns produced by the stomatogastric ganglion (STG). These data suggest that the dopaminergic and histaminergic systems in H. americanus appear relatively early in development and that the effects of each are largely maintained through development.