ORIGINS OF HORIZONTAL CELL SPECTRAL RESPONSES IN THE RETINA OF MARINETELEOSTS (CENTROPOMUS AND MUGIL SP)

Intracellular recording and marking of horizontal cells (HCs) were car ried out in isolated retinas of marine teleosts (Centropomus and Mugil sp.) to identify the cellular origins of different spectral types of S-potential, The spectral responses recorded under mesopic conditions were classified into four types: photopic L, biphasic C(R/G), biphasic C(G/R), and scotopic L(sL), Intracellular marking with Lucifer yellow (LY) or Procion yellow (PY) revealed that in the Centropomus retina a n L-type response was recorded from H1 and H2 cells, C(R/G)-type from H3 cells, and sL-type from H4 cells, However, in 20% of microelectrode penetrations from the photoreceptor surface, the sequential order of response appearances was found to be L-, sL-, and C(R/G)-types. In thi s species, thick dendritic processes of H3 and H4 cells are distribute d at the same level as the cell body, In the Mugil retina, on the othe r hand, L-type response was recorded from H1 cells, C(G/R)-type from H 2 cells, C(R/G)-type from H3 cells, and sL-type from H4 cells, this se quential arrangement being very regular, In both species, the cone-con nected H1 cells are small and possess an axon, while the two other con e HCs as well as rod-connected H4 cells are axonless, Earlier (Negishi et al., 1988) and present findings indicate that there is a wide vari ety of HC morphology and functional organization in the teleost retina . (C) 1997 Wiley-Liss, Inc.