Astrocytic Glutamate Transporters and Migraine

Glutamate levels and lifetime in the brain extracellular space are dinamically regulated by a family of Na+- and K+-dependent glutamate transporters, which thereby control numerous brain functions and play a role in numerous neurological and psychiatric diseases. Migraine is a neurological disorder characterized by recurrent attacks of typically throbbing and unilateral headache and by a global dysfunction in multisensory processing. Familial hemiplegic migraine type 2 (FHM2) is a rare monogenic form of migraine with aura caused by loss-of-function mutations in the alpha 2 Na/K ATPase (alpha 2NKA). In the adult brain, this pump is expressed almost exclusively in astrocytes where it is colocalized with glutamate transporters. Knockin mouse models of FHM2 (FHM2 mice) show a reduced density of glutamate transporters in perisynaptic astrocytic processes (mirroring the reduced expression of alpha 2NKA) and a reduced rate of glutamate clearance at cortical synapses during neuronal activity and sensory stimulation. Here we review the migraine-relevant alterations produced by the astrocytic glutamate transport dysfunction in FHM2 mice and their underlying mechanisms, in particular regarding the enhanced brain susceptibility to cortical spreading depression (the phenomenon that underlies migraine aura and can also initiate the headache mechanisms) and the enhanced algesic response to a migraine trigger.