Activities in cellular signalling pathways: a two-edged sword?

The maintenance and adaptive plasticity of neural circuitry requires the coordinated activities of an array of signal transduction systems. These different signalling systems play critical roles in carving out and modifying functional neural circuitry in development and adult plasticity. Ironically, aberrant activity in these systems may sever neural connections and take the lives of neurons in a variety of disorders including Alzheimer's disease. A rather complex set of circumstances must be taken into account when considering the consequences of activity in pathways that regulate neuroarchitecture. The specific signalling pathways activated, their levels of activation, activity in other pathways, and environmental conditions are among the factors that enter into the equation for determining whether use is a boon or a bane.