Figure 4.

T-type Ca²⁺ channels modulate the basal [Ca²⁺] at subthreshold potentials in the primary dendrite of mitral cells. A, Mitral cells were loaded with Alexa-594 and Ca²⁺ Green-1 as shown on the fluorescent images (left). Rectangle represents the scanned area; red polygon represents the region of interest. Basal [Ca²⁺] was expressed as G/R. A 4-s-long hyperpolarizing step from V_rest to V_hyper caused a reduction in basal [Ca²⁺] (τ_decay = 1.20 s, n = 5). B, A 4-s-long hyperpolarizing step significantly decreased the basal [Ca²⁺] in the apical dendrite and tuft. Black dots connected with thick black lines indicate the mean of 7 and 5 individual experiments (thin lines) in the apical tuft and apical dendrite (Ad), respectively. *p < 0.05; **p < 0.01. C₁, C₂, Sinusoidal modulation of membrane potential above and below normal resting potential modulates basal [Ca²⁺]. Voltage-dependent increases in basal [Ca²⁺] are attenuated by T-type channel blockers NNC 55–0396 (50 μm) and Z941 (10 μm). Bar charts on the right represent the population effect of Z941 on the amplitudes of subthreshold Ca²⁺ influx (control, black, n = 4; Z941, gray, n = 4, 5–20 min bath application). ***p < 0.001.