Presence and development of thyrotropin-releasing hormone-immunoreactive amacrine cells in the retina of a teleost, the brown trout (Salmo trutta fario)

The presence of thyrotropin-releasing hormone-immunoreactive (TRHir) amacrine cells is described for the first time in the retina of a teleost, These amacrine cells were mostly located in the inner nuclear layer, with occasional perikarya in the ganglion cell layer. Their processes formed a conspicuous plexus at the level of the gang lion cell perikarya. The TRHir amacrine cells appeared in posthatching stages, with the total number in retinas of juveniles approximately four times the number of cells in adults, Two types of TRHir cells, large and small, can be distinguished in developing stages, small cells outnumbering large cells. The TRHir cells of adults appears mainly to correspond to large, multistratified amacrine cells of developing stages. The possibility of transient expression of TRH in small amacrine cells during development is discussed. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.