![]() ![]() Whole retinas were kept in the fixative fluid for 2 h at room temperature, heated in PBS at 65☌ for 30 min, and carefully rinsed with 5% sucrose in 0.2 M cacodylate buffer (pH 7.4) to eliminate phosphate ions. They were perfused through the heart with 2% formaldehyde and 1% glutaraldehyde in Sörensen phosphate buffer (pH 7.4), after rinsing the vascular tree with carboxygenated Ames medium (Sigma) containing 40 mM glucose. injection of 0.1 ml of a solution containing 5% ketamine HCl (Ketaset Fort Dodge Laboratories, Fort Dodge, IA) and 1% xylazine (Rompun Bayer, Shawnee Mission, KS). Briefly, adult mice, homozygous for PLAP cDNA, were anesthetized by i.p. Details of the technique of specimen preparation and staining for alkaline phosphatase activity were described ( 21). These animals were obtained by introducing into the mouse genome PLAP cDNA linked to a promoter sequence of the gene for TH ( 21). GABA acts on the ionotropic receptors clustered at the postsynaptic active zone, whereas dopamine diffuses to more distant, slower-acting metabotropic receptors.Ī transgenic mouse line was used in which DA cells in the retina expressed human placental alkaline phosphatase (PLAP) on the outer surface of the cell membrane. We suggest that the synapses between retinal dopaminergic neurons and AII amacrine cells are GABAergic and that both GABA and dopamine are released by the presynaptic endings. D1 and D2/3 dopamine receptors, on the other hand, do not form clusters on the surface of the perikarya of AII amacrine cells. ![]() We found that at the interface between the dendrites of the dopaminergic neurons and the AII amacrine cell perikarya clusters of postsynaptic γ-aminobutyric acid type A (GABA A) receptors are situated in register with aggregates of presynaptic organelles immunoreactive for GABA, the GABA vesicular transporter, and the vesicular monoamine transporter-2. ![]() We used triple-label immunocytochemistry and confocal microscopy to identify the receptors contained within the postsynaptic active zone of these synapses in both mouse and rat retinas. In the retina, dopaminergic amacrine (interplexiform) cells establish multiple synapses on the perikarya of AII amacrines, the neurons that distribute rod signals to on- and off-cone bipolars. ![]()
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