Distribution of serotonergic and dopaminergic nerve fibers in the salivary gland complex of the cockroach Periplaneta americana.
BACKGROUND
The cockroach salivary gland consists of secretory acini with peripheral ion-transporting cells and central protein-producing cells, an extensive duct system, and a pair of reservoirs. Salivation is controlled by serotonergic and dopaminergic innervation. Serotonin stimulates the secretion of a protein-rich saliva, dopamine causes the production of a saliva without proteins. These findings suggest a model in which serotonin acts on the central cells and possibly other cell types, and dopamine acts selectively on the ion-transporting cells. To examine this model, we have analyzed the spatial relationship of dopaminergic and serotonergic nerve fibers to the various cell types.


RESULTS
The acinar tissue is entangled in a meshwork of serotonergic and dopaminergic varicose fibers. Dopaminergic fibers reside only at the surface of the acini next to the peripheral cells. Serotonergic fibers invade the acini and form a dense network between central cells. Salivary duct segments close to the acini are locally associated with dopaminergic and serotonergic fibers, whereas duct segments further downstream have only dopaminergic fibers on their surface and within the epithelium. In addition, the reservoirs have both a dopaminergic and a serotonergic innervation.


CONCLUSIONS
Our results suggest that dopamine is released on the acinar surface, close to peripheral cells, and along the entire duct system. Serotonin is probably released close to peripheral and central cells, and at initial segments of the duct system. Moreover, the presence of serotonergic and dopaminergic fiber terminals on the reservoir indicates that the functions of this structure are also regulated by dopamine and serotonin.
Baumann
Otto
O
Institut für Biochemie und Biologie, Zoophysiologie, Universität Potsdam, Lennéstr, 7a, 14471 Potsdam, Germany. obaumann@rz.uni-potsdam.de
Dames
Petra
P
Kühnel
Dana
D
Walz
Bernd
B
D000818:Animals; D000911:Antibodies, Monoclonal; D004298:Dopamine / Q000276:immunology / Q000378:metabolism*; D004525:Efferent Pathways / Q000737:chemistry / Q000378:metabolism; D005260:Female; D008297:Male; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009412:Nerve Fibers / Q000737:chemistry* / Q000378:metabolism*; D010526:Periplaneta; D018987:Salivary Ducts / Q000294:innervation; D012469:Salivary Glands / Q000033:anatomy & histology / Q000294:innervation; D012701:Serotonin / Q000276:immunology / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D012701:Serotonin; D004298:Dopamine