[Immunohistochemical studies of the role of dopaminergic retinal cells in neuronal light adaptation].
BACKGROUND
Tyrosine hydroxylase (TH) like immunoreactivity was investigated in frozen sections and in whole mounts of the chicken and bovine retina in order to investigate the distribution and role of dopaminergic structures in retinal circuiting.


METHODS
By means of monoclonal antibodies against tyrosine hydroxylase the dopaminergic retinal structures were marked and their distribution determined by light microscopy.


RESULTS
In both species TH-positive labelled cell bodies were localized in the innermost part of the inner nuclear layer (INL) close to the inner plexiform layer (IPL). In addition, in bovine retina TH-positive cell bodies were also located in the IPL and in the ganglion cell layer. TH-positive cell bodies gave rise to one to four fibers, which extended into sublayer 1 of the inner plexiform layer. In this sublayer fine fibers with button like structures were visible establishing a dense TH-positive plexus. In both species within this plexus small spots, free of any staining and surrounded by a ring of TH-positive fibers, could be observed. These "ring-like" structures were twice as frequent in bovine than in chicken retina. One to three thicker fibers per cell project into sublayer 3 and 4-5 of the IPL. In sublayer 3 of chicken retina they ramified into very long and fine fibers with small "bouton" like knobs. In bovine retina similar long fine fibers are found predominantly in sublayer 4-5. In sublayer 4-5 of the chicken retina the fibers were short and thick and shows a clear ramification pattern. They were found to be in close contact to the fibers of adjacent TH-positive cells. In bovine retina thin fibers arose from the TH-positive plexus in sublayer 1, passed through the INL and ramified within the outer plexiform layer (OPL). In chicken retina fibers only occasionally entered the INL; in the OPL fibers never could be observed. The appearance of TH-positive cells in the bovine and chicken retina resembles that of TH-positive cells found in other vertebrates. In whole mounted retinae from chicken and bovine the mean-density of TH-positive cells was 23 cells/mm2 and 27 cells/mm2, respectively.


CONCLUSIONS
The fact that in the rod dominated bovine retina dopaminergic "ring-like" structures are observed more frequently than in the chicken retina may give a morphological hint that dopaminergic amacrine cells might be involved in neuronal retinal light adaptation.
Datum
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KH
Abteilung für Pathophysiologie des Sehens und Neuroophthalmologie Universitäts-Augenklinik Tübingen.
Kohler
K
K
Zrenner
E
E
D000221:Adaptation, Ocular / Q000502:physiology*; D000818:Animals; D002417:Cattle; D002645:Chickens; D003712:Dendrites / Q000648:ultrastructure; D004298:Dopamine / Q000502:physiology*; D007124:Immunoenzyme Techniques; D010786:Photoreceptor Cells / Q000033:anatomy & histology / Q000201:enzymology; D012160:Retina / Q000033:anatomy & histology / Q000201:enzymology*; D013045:Species Specificity; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*
D014446:Tyrosine 3-Monooxygenase; D004298:Dopamine
Immunhistochemische Untersuchungen zur Rolle dopaminerger retinaler Zellen bei der neuronalen Helligkeitsanpassung.