So-called interplexiform cells immunoreactive to tyrosine hydroxylase or somatostatin in rat retina

The morphology of so-called interplexiform (IP) cells immunoreactive to tyrosine hydroxylase (TH) or somatostatin (SOM) in the rat retina was described in comparison with those in the carp retina. In frozen cross-sections of the rat retina, many processes of TH-like immunoreactive cells were found to extend toward the outer plexiform layer (OPL), forming a thin layer of network fibers. A few of them further extended into the photoreceptor cell layer; such fibers were never found in the carp retina. Some processes of SOM-like immunoreactive cells in the rat retina were found to travel across the inner nuclear layer and appeared to poorly develop a network at the OPL. In the carp retina, on the other hand, only one exceptional cross-section contained such an ascending process.