Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

We investigated expression of Mel1a and Mel1b melatonin receptors subtypes in discrete regions of rat brain and retina. Western blots using anti-Mel1a receptor antibody showed a 37kD band in neocortex, hypothalamus, midbrain, cerebellum and medulla. RT-PCR revealed mRNA expression of both subtypes in the same brain regions. In rat retina the Mel1a receptor in rat retina exhibited a single 37kD immunoreactive band and immunocytochemical localization to both the inner and outer plexiform layers. Expression of Mel1a receptor mRNA in the rat retina was confirmed by RT-PCR and in situ hybridization. Mel1a receptor transcripts were localized to the following three retinal cell types: ganglion, amacrine and horizontal cells. Modulation of GABAA receptor mediated whole-cell currents by melatonin was examined in rat brain slices. Melatonin (1 nM) enhanced GABAA receptor- mediated currents in the suprachiasmatic nucleus (SCN) neurons while reducing the currents in the hippocampal CA1 neurons. In HEK293 cells expressing recombinant GABAA receptors, melatonin enhanced GABAA receptor-mediated currents only in cells cotransfected with Mel1a receptor and depressed currents in cells coexpressing the Mel1b receptor. Melatonin, acting on specific melatonin receptor subtypes, exerts opposite effects on GABAA receptor function, providing evidence for functional differences of these subtypes.

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Presentation Number SAbrown0866
Keywords: melatonin, receptors, rat, nervous system