Fig. 5

Effect of blocking the voltage-gated Ca²⁺ channels on the neuronal depolarization elicited near the site of CSD induction by CSD threshold and just subthreshold KCl stimuli. A Representative membrane potential traces recorded in response to a CSD threshold KCl stimulus in a L2/3 pyramidal cell located near the KCl puffer (as in Figure 1) in the absence (ctrl, red trace) and presence (Ni²⁺, green trace) of a saturating concentration of Ni²⁺ (5 mM) (upper panel). The corresponding, simultaneously recorded, IOS changes are shown in the lower panel. Ni²⁺ completely inhibited the CSD peak depolarization (3^rd peak) as well as the steep CSD IOS rise. Ni²⁺ also eliminated the 2^nd peak of the early depolarization as well as the slow IOS rise preceding CSD initiation, and it inhibited 45 % of the amplitude (relative to the resting potential) of the 1^st peak of the depolarization elicited by the CSD threshold stimulus. B Representative membrane potential traces recorded in response to a CSD just subthreshold KCl stimulus in the same L2/3 pyramidal cell of panel A in the absence (ctrl, black trace) and presence (Ni²⁺, green trace) of Ni²⁺. Ni²⁺ inhibited 57 % of the amplitude (relative to the resting potential) of the 1^st peak of the depolarization elicited by the just subthreshold stimulus, and eliminated both the 2^nd peak and its shoulder, thus decreasing the duration (at half amplitude) of the just subthreshold depolarization from 11.7 to 2.1 s. C Average peak voltage of the depolarizations produced by KCl stimuli of increasing intensity in the presence of Ni²⁺ (5 mM) as a function of stimulus intensity (KCl puff duration) (n= 4; N =4). Inset: representative membrane potential traces recorded in response to subthreshold KCl stimuli of increasing intensity up to the threshold stimulus in the presence of Ni²⁺ (5 mM) in the same L2/3 pyramidal cell of panels A, B