Figure 7. Loss of β2 eliminates the diurnal difference in firing rate, and rescue of inactivation with β2N restores daytime firing rates in SCN neurons.

(a) Spontaneous action potential activity from representative day (BK_i) and night (BK_s) WT neurons. Dotted line (a,c,d) denotes −50 mV. (b) In WT SCNs, BK_i neurons fired at higher frequencies than BK_s, similar to the average day–night difference in firing. β2 KO neurons did not exhibit a diurnal difference in frequency, and during the day, fired at levels similar to WT night. Application of β2N^ΔFIW to daytime β2 KO neurons had no effect on frequency, but β2N increased firing rate to WT levels. (c) Day (BK_s) and night (BK_s) β2 KO neurons. (d) Day β2 KO neurons with 50 μM β2N (BK_i) or 50 μM β2N^ΔFIW (BK_s). All values are mean±s.e.m. n values: WT: BK_i (17), BK_s (10), day (17), night (20); β2 KO: day (19), night (19), β2N^ΔFIW (20), β2N (19), β2N/pax (8), and pax (8).