Serotonin-like immunoreactivity in the retina of the clawed frog Xenopus laevis.
Using an antiserum directed against serotonin, we have studied the morphology and distribution of serotonin-containing and serotonin-accumulating neurons in the retina of Xenopus laevis. Endogenous serotonin-like immunoreactivity was found in two classes of amacrine cell, one class of bipolar cell and a few centrifugal fibres. Kainic acid-induced depletion of serotonin, under various conditions, enabled us to determine the distribution of stained bipolars, amacrine cells and centrifugal fibres within the meshwork of serotonin-like immunoreactivity-labelled processes. Kainic acid-induced release of serotonin by bipolar cells is calcium dependent. Stimulation of release by kainic acid as well as the fact that all serotonin-like immunoreactive bipolar cells ramify in sublayer 1 of the inner plexiform layer suggest that serotonergic bipolars are OFF centre cells. Release of serotonin from amacrine cells is largely calcium independent. Serotonin-containing amacrines send primary dendrites into layer 1 of the inner plexiform layer; short off-shoots from the primary dendrites descend into sublayers 3-5 in which they ramify into a fine network. Serotonergic amacrines have an uneven distribution in the Xenopus retina. Their highest density occurs in the posterolateral quadrant, whereas large portions of the anteromedial quadrant lack serotonin-like immunoreactivity altogether. The uneven distribution of serotonin-containing elements in the Xenopus retina with its peak falling onto the retinal area which generates binocular vision, suggests its involvement in binocular perception.
Schütte
M
M
Department of Ophthalmology, NYU Medical Center, NY 10016.
Witkovsky
P
P
D000818:Animals; D002452:Cell Count; D007150:Immunohistochemistry; D009412:Nerve Fibers / Q000737:chemistry; D009474:Neurons / Q000166:cytology; D012160:Retina / Q000033:anatomy & histology / Q000737:chemistry*; D012701:Serotonin / Q000032:analysis*; D014982:Xenopus laevis
D012701:Serotonin