Immunohistochemical characterization of NMDA, kainic acid and aspartate-induced released of GABA in chick retina

IMMUNOHISTOCHEMICAL CHARACTERIZATION OF NMDA, KAINIC ACID AND ASPARTATE-INDUCED RELEASED OF GABA IN CHICK RETINA^*

KARIN C. CALAZA, FERNANDO G. DE MELLO AND PATRÍCIA F. GARDINO

Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, RJ, Brazil

It has been shown that glutamate and its agonists, NMDA, kainic acid (KA) and aspartate (ASP) can promote the release of GABA from isolated retina and retina cell cultures. In addition, dopamine (DA) modulates the release induced by NMDA. The aim of this work is to determine, qualitatively and quantitatively the GABAergic cell types that are affected by glutamatergic agonists and DA in isolated mature and embryonic chick retina. Embryonic day fourteen (E14) and two- to seven-day post-hatched (P2-7) retinas were incubated with different glutamatergic agonists and DA at C. GABA containing neurons (GABA+) were identified immunohistochemically. In P7 animals, the stimulation of GABA release with NMDA or ASP resulted in 50% decrease in the number of GABA+ amacrine cells. No change in GABA+ horizontal cell number was detected. DA partially inhibited (50%) the decrease in GABA+ amacrine cells by the treatment with either NMDA or ASP. KA induced a decrease of both GABA+ amacrine (60%) and horizontal cells (50%). However, DA did not interfere with the release stimulated by KA. NMDA, KA and ASP stimulated retinas show a punctate labeling of the inner plexiform layer, differing from the uninterrupted labeling in the control retina. The NMDA effect on GABAergic cell number was the same for E14 or P2-7 retinas, i.e., a 50% decrease in the number of GABA+ amacrine cell number. In addition, DA partially (50%) reduced the NMDA effect. The KA effect on the embryonic retina repeated the pattern seen in P2-7 retinas, a reduction of both GABA+ amacrine (60%) and horizontal cells (50%). However, as opposed to what was observed in P2-7 retinas, DA significantly reduced the decrease of GABA+ cells induced by KA in E14 retinas. From this data, it can be concluded that NMDA induced GABA release from amacrine cells is modulated by dopamine. This effect is independent of the developmental stage of the retina, since it is observed in both, E14 and P2-P7. On the other hand, KA stimulates GABA release from both types in E14 and P2-P7 chicken. However DA modulates this process in E14 retina, but not in P2-7 retinas. — ( June 27, 2000 ) .

Publication Dates

• Publication in this collection
  05 Oct 2000
• Date of issue
  Sept 2000