Differential localization of GABAB receptors in the mouse retina

THE mRNA distribution of the two cloned GABAB receptor variants, GABABR1a and −R1b, was analysed in the retina by non-radioactive in situ hybridization. GABABR1a transcripts were found in the inner nuclear and ganglion cell layers, probably in horizontal, amacrine and ganglion cells, whereas GABABR1b transcripts were detected in the ganglion cell layer only. Together with a recent immunohistochemical localization of GABABR1 in the retina, this indicates a differential targeting of the receptor variants to pre- and postsynaptic sites with GABABR1a and −R1b localized to axonal and dendritic compartments, respectively. In this way, inhibition of neurotransmitter release and slow postsynaptic inhibition could be provided by receptor variants derived from the same gene.