Dr. Gyula Lázár, University of Pécs Medical Faculty, Department of Human Anatomy Pécs

The optic tectum is the most important visual centre from fish to birds. Most studies on this system were performed on frogs. In the last 15 years primarily the neurotransmitters and modulators of the tectum have been studied.

The tectum projects to the middle thalamic neuropil. Tectal afferents establish connections with neurons of the central and lateral thalamic nuclei. From these nuclei originates a pathway that terminates in the telencephalon, mainly in the striatum. Most cells of the two thalamic nuclei mentioned contain nitric oxide synthase and several of them are immunoreactive for NPY. It is not known whether the two populations of neurons are composed of interneurons, projection neurons or both.

The optic tectum is reciprocally connected with the isthmic nucleus. The majority of isthmic cells are cholinergic, but several cells are serotoninergic and both types send axons into the tectum. The relationship of their terminals and peptidergic and GABAergic tectal cells is not known.

We will identify tectal and thalamic projection neurons with retrograde labelling. Using immunohistological techniques we attempt to identify some of their peptides and transmitters. The expected results may help understanding function of the frog visual system.