Abstract:
Adenosine receptors (AR) are activated by extracellular adenosine, and are involved in many different functions including neuromodulation, mediation of inflammatory conditions, and cell death. In the brain, adenosine has been shown to provide neuroprotection against various insults including glutamate mediated excitotoxicity, hypoxia and ischemia. The expression of adenosine receptor subtypes A1,A2A, A2B and A3 have been demonstrated in various regions of the central nervous system (CNS), however, very little information is available on the expression of these receptors in the cochlear nucleus (CN). Understanding the expression and distribution of AR in the cochlear nucleus would aid in determining whether adenosine may have a role in cochlear nucleus function and degenerative changes in the CN that lead to hearing disorders. In this study, immunohistochemistry was used to characterise the expression of A1, A2A and A3Rs in the mouse CN, obtained from developmental ages P0, P6, P14 and P22. Double labelling studies were performed with fluorescent Nissl and antibodies to Microtubule Associated Protein 2 (MAP2) and Glial Acidic Fibrillary Acid Protein (GFAP) to aid with the structural localisation of these receptors. Inconsistent results were obtained with the A1R antibody and so it was not possible to identify and characterise the expression of A1 in the CN. Two patterns of labelling were observed with the antibodies to A2ARs, which included labelling around granule cell-like soma and on glial cells. The A3R labelling was described as dendritic like and was found throughout the P22 CN. These labelling patterns were observed in both the P6 and P14, but could not be characterised in the P0 CN. The study concluded that A2ARs are found on the membrane of granule like somata and glial cells, whilst the A3Rs are found on neuronal dendrites throughout the CN. These data provide a platform for further studies to determine the role of AR and adenosine in the normal and abnormal function of the CN.
