CALRETININ IN NEUROCHEMICALLY WELL-DEFINED CELL-POPULATIONS OF RABBITRETINA

In the rabbit retina, parvalbumin has been localized selectively to AI I amacrine cells, while 28 kDa calbindin could be detected in horizont al cells, in one type of depolarizing cone bipolar cell and a populati on of wide-field amacrine cells. The distribution of the third neurona l calcium binding protein, calretinin, however, has not been studied t o date in detail in the rabbit retina. Therefore in this study we aime d to describe the overall distribution of calretinin in the different retinal layers and the possible colocalization pattern with other neur ochemical marker molecules. A few cone photoreceptor cells were found to be labeled, whereas the outer plexiform layer was free from immunor eactive elements. In the most proximal row of the inner nuclear layer amacrine cells were labeled, while more distally a few cells emitted b eaded axon-like processes toward the outer retina. There were large (1 8-28 mu m in diameter) cells labeled in the ganglion cell layer, of wh ich many apparently had their axon stained. Some of the calretinin imm unoreactive amacrine cells (the AII neurons) also contained parvalbumi n. Colocalization of calretinin and 28 kDa calbindin could not be asce rtained in the same amacrine cell populations, nor was tyrosine hydrox ylase present in calretinin-containing cells. There was partial coloca lization of calretinin in the gamma-aminobutyric acid-positive amacrin e cell population. Parvalbumin containing ganglion cells were also pos itive for calretinin; however, the calretinin-positive ganglion cells were more numerous. gamma-Aminobutyric acid could be colocalized in so me calretinin-positive neurons of the ganglion cell layer. (C) 1997 El sevier Science B.V.