Early appearance and transient expression of putative amino acid neurotransmitters and related molecules in the developing rabbit retina: An immunocytochemical study

Abstract

We have studied, by immunocytochemistry, the ontogeny of GABA, glycine, glutamate, glutamine, and taurine-containing cells in the rabbit retina. Amacrine cells show GABA immunoreactivity by embryonic day 25 (E25) and throughout postnatal life. By contrast, ganglion cells and horizontal cells are only transiently GABA-immunoreactive (-IR); few appear GABA-IR by the third postnatal week. At maturity, glycine is present in amacrine cells and in some bipolar cells. During development, putative ganglion cells transiently contained glycine between E25 and postnatal day 3 (P3), whereas immunolabelling in presumed amacrine cells and bipolar cells persists after birth. Ganglion cells, bipolar cells, photoreceptors, and some amacrine cells are glutamate-IR in the adult retina. Glutamate immunoreactivity first appears in the somata and processes of cytoblastic cells by E20 and is prominent by E25. Surprisingly, ganglion cells are not strongly glutamate-IR until just before eye-opening, at postnatal day 10 (P10), coincident with the appearance of glutamine in their somata and in Müller glial cells. Bipolar cells are glutamate-IR before they or Müller cells contain high levels of glutamine (at P10). Glutamate immunoreactivity in photoreceptors is progressively restricted to the inner segments by eye-opening. At no stage are presumed horizontal cells glutamate-IR or glutamine-IR, but some amacrine cells show glutamate- and glutamine-IR by P10. Taurine is localized to photoreceptors and Müller glial in the adult retina. Some cytoblasts are taurine-IR at E20; with ensuing development, taurine labelling becomes restricted primarily to Müller cells and photoreceptors; some putative bipolar cells may also be labelled. However, for a few days around birth, cells resembling horizontal cells, also show taurine immunoreactivity. The early appearance and often transient expression of these amino acids in retinal cells suggests that these neuroactive molecules may be involved in the structural and functional development of the retina.

Expression of GABA transporter subtypes (GAT1, GAT3) in the adult rabbit retina

“…GAT1, GAT3 and GABA double immunostaining GABA immunoreactivity was seen predominately in sublayers in the inner plexiform layer, in amacrine cells and in ganglion cells, weakly in some bipolar cells and irregularly in the outer plexiform layer (OPL), as has been previously described (Agardh & Ehinger 1983;Messersmith & Redburn 1992;Pow et al 1994;Young 1994). GAT1 had a very similar distribution, and double labeling showed that it often but not always colocalized with the GABA immunoreactive cells (Fig.…”

The expression of GABAAreceptors during the development of the rabbit retina

“…Like in the brain, uptake, synthesis, storage, and release of gammaaminobutyric acid (GABA) are some of the characteristic properties of GABAnergic neurones in the retina (Redburn 1992, Marc, 1992. GABA is synthesized already prenatally, being detectable at around E25 with immunohistochemistry (Pow et al 1994). The synthesizing en-zyme, GAD, may appear even earlier (Redburn, 1992).…”

Developmental Changes in the Neurotransmitter Regulation of Correlated Spontaneous Retinal Activity

“…Although cholinergic and GABAergic amacrine-to-ganglion cell connections have been documented at this time (Greiner and Weidman, 1981), the source of glutamate at this stage is less clear. The absence of bipolar synapses at this time raises the possibility that glutamate may be secreted in a paracrine manner by ventricular cells or precursors to bipolar cells (Pow et al, 1994). Alternatively, potential transient connections between immature glutamatergic photoreceptors, observed to extend synaptophysinpositive processes into the IPL at this stage, may act as a source of glutamatergic transmission (Johnson et al, 1999).…”