Apparatus is provided including one or more electrodes, adapted to be applied to an otic-ganglion site of a patient selected from the group consisting of: an otic ganglion, an associated neural tract of the otic ganglion, an afferent fiber going into the otic ganglion, and an efferent fiber going out of the otic ganglion. The apparatus further includes a stimulator, configured to drive the one or more electrodes to apply a current to the otic-ganglion site, and to configure the current to activate the otic-ganglion site sufficiently to induce at least one effect selected from the group consisting of: a change in cerebral blood flow (CBF) of the patient, and a change in permeability of a blood-brain-barrier (BBB) of the patient. Other embodiments are also described.