Adrenergic Receptors on Astrocytes Modulate Gap Junctions

Adrenergic receptors in astrocytes have both direct and indirect impact on intercllular communication in the nervous system. Direct mechanisms include activation of second messenger pathways that produc posttranslational modifications of the gap junction proteins [connexins (Cxs)] or activate transcription factors or other procsses such as miRNAs that dictate or modify Cx gene expression or protein translation. These direct effects change the strength of intercllular communication through modifying open probability of the gap junction channels, altering balanc between delivery to the membrane and degradation or through regulation of transcript abundanc. Indirect actions with potentially profound implications for glial and neuronal network activity include alterations in the intracllular concntration of metabolites, energy-supplying molecules and second messengers, thereby changing the diffusional driving forc responsible for intercllular spread. Although direct effects target the gap junction channels themselves to affect gating, assembly, and turnover, indirect action to liberate intracllular molecules may also produc rapid dynamic changes in spread of these factors throughout the coupled networks.