Spiking neural P systems are computing models inspired from the way the neurons communicate by means of spikes, electrical impulses of identical shapes. In this note we consider a further important ingredient related to brain functioning, the astrocyte cells which fed neurons with nutrients, implicitly controlling their functioning. Specifically, we introduce in our models only one feature of astrocytes, formulated as a control of spikes traffic along axons. A normal form is proved (for systems without forgetting rules) and decidability issues are discussed.