Differential expression of GAD and GAD during the development

The development of synthetic enzymes in the GABAergic system (GAD and GAD ) of the rat retina was analyzed from birth to the 67 65 4th postnatal week by the reverse transcriptase polymerase chain reaction (RT–PCR) and by immunohistochemistry. As previously observed for GABA, immunoreactive GAD profiles are seen clearly in the inner retinal layers at birth. At the end of the 1st week of 67 postnatal life, immunolabeling is detected in amacrine and/or ganglion cells and in horizontal cells. GAD immunoreactivity is 67 transiently expressed in horizontal cells and disappears during the 3rd postnatal week. GAD however does not develop until the 5th 65 postnatal day. Immunolabeling is detected in the processes layering the inner plexiform layer (IPL) before being detected in the amacrine and/or ganglion cell bodies. The appearance of transcripts for GAD coincided with the appearance of the proteins. A transient form of mRNA transcripts of the GAD gene containing an extra exon (ES-exon) is also observed which disappears progressively from birth to 67 the 4th postnatal week. This form synthesizes a truncated, enzymatically inactive protein, which could participate in the regulation of GABA synthesis from glutamate present at high levels during retinogenesis.  2001 Elsevier Science B.V. All rights reserved. Theme: Development and regeneration Topic: Visual system