Fig. 7

Blocking Ca_V2.1 Ca²⁺ channels prevents CSD initiation by suprathreshold stimuli at least four times larger than the control CSD threshold. Upper panels: representative IOS changes recorded at different distances from the site of KCl application (cf inset in Figure 1A) in response to a CSD threshold KCl stimulus in control (left) and in the presence of 400 nM ω-AgaIVA (right). Lower panels: IOS changes recorded in the same slice at the same distances in response to largely suprathreshold KCl stimuli of duration 4 times threshold (left) and 13 times threshold (right) in the presence of 400 nM ω-AgaIVA. After blocking Ca_V2.1 channels, almost no IOS changes were recorded in response to threshold stimulation and only slow non-propagating IOS changes whose amplitude rapidly declined with distance from the site of KCl application were recorded in response to a stimulus 4 times larger than the threshold stimulation. The steeper and biphasic IOS change recorded at 150 µm in response to a KCl stimulus 13 times threshold and the corresponding IOS change recorded at 100 um (which is distorted by the large artefactual inward IOS change produced by the very high KCl concentration) can be interpreted as indicative of a CSD-like event propagating for a short distance (up to 250 µm) from the site of KCl application. Farther than this distance, the amplitudes of the IOS changes rapidly declined