Effects of intraocular administration of glutamate on dopaminergic neurons in rat retina

• Published in: Japanese Journal of Pharmacology Vol. 58; no. suppl.1; p. 183
• Main Authors: Hamahashi, Takatoshi, Kamisaki, Yoshinori, Okada, Chiharu, Itoh, Tadao, Tamai, Akihiko
• Format: Journal Article
• Language: English
• Published: The Japanese Pharmacological Society 1992
• ISSN: 0021-5198; 1347-3506
• DOI: 10.1016/S0021-5198(19)49047-1

Previously, we reported that water-immersion restraint stress produced increases in dopamine (DA) and glutamate (Glu) contents in retina of the rat. We also found that Glu increased in aromatic amino acid decarboxylase (AAAD) activity of the isolated retina. In the present study, we investigated the effects of intraocular administration of Glu on rat retinal neurons, especially dopaminergic neurons. Male Wistar strain rats (6-8 weeks) housed under a 12-hr light/dark cycle (lights on 07：00-19：00) were used in these studies. The experiments were conducted between 13：00 and 15：00. Glu (0.02 - 10 μmol) was injected into the right eye and an equal volume of saline into the left eye as control. One hour after the injections, rats were sacrificed by decapitation and their retinas were quickly removed. DA contents and AAAD activity were measured. Intraocular Glu injection caused no significant change in DA contents of retina, but significant increase in AAAD activity to 139% of that in the control retina. These data suggest that exogenously administered Glu may stimulate not only DA synthesis through the activation of AAAD but also DA degradation. Further study is undertaken to clarify which subclasses of Glu receptors are involved in the effect of Glu on DA neurons.