DENSITY RATIO OF DOPAMINERGIC VERSUS SEROTONERGIC CELLS CORRELATES WITH CONE-TO-ROD RATIO IN TELEOST RETINAS

Dopaminergic and serotonergic cells were visualised immunohistochemica lly with antibodies against tyrosine hydroxylase and serotonin in reti nal wholemounts of eight teleosts from different habitats and with dif ferent rod-to-cone ratios. The cell densities were calculated, and the density ratio of dopaminergic cells versus serotonergic cells was com pared among theses fish species. The density ratio was high (1.9-2.7) in three out of the four species of cichlid fish studied with cone den sities roughly equalling rod densities, medium in roach (0.8) where ro ds dominate cone numbers, and low in deep-sea fish (0.2-0.4) with pure rod retinas. These observations confirm earlier findings on the speci es-specificity of the ratio of dopaminergic versus serotonergic cells in the retina and further demonstrate a close correlation between the rod-to-cone ratio, and the density ratio of dopaminergic versus seroto nergic cells in the inner retina. The possible significance for the pr ocessing of photopic and scotopic information in the inner retina is d iscussed. (C) 1997 Elsevier Science Ireland Ltd.