Figure 6.

Calcium effects on persistent firing. (a) Recordings from an Htr5b-EGFP-positive hippocampal interneuron in normal (top; 2 mM) and low (bottom; 0.5 mM) Ca²⁺ ACSF. Note the firing lasts dramatically longer in low Ca²⁺ than in normal ACSF. (b) Bar graph showing the number of evoked spikes required to induce persistent firing remains unchanged in low Ca²⁺ conditions (all data normalized to the 2 mM condition in the same cells; 1 mM; n = 9, 0.5 mM; n = 11 and 0 mM; n = 10). Increasing the Ca²⁺ concentration to 5 mM slightly reduced the number of evoked spikes required to induce persistent firing (n = 4). (c) The duration of persistent firing is significantly increased in low Ca²⁺ (0.5 mM and 0 mM) and reduced in high Ca²⁺ (5 mM). All statistics are paired-sample comparisons relative to 2 mM Ca²⁺ in the same cell, * P < 0.05. All summary data are mean ± s.e.m. All data are from Htr5b-EGFP-positive hippocampal interneurons near the SR-SLM border.