Fig 5.

Allopregnanolone blocks T-type calcium channels (T-channels) in a voltage-dependent manner and attenuates rebound burst firing in subicular neurones. (a) Original traces from a representative subicular neurone displaying that allopregnanolone (Allo) reduced the amplitude of inward calcium currents evoked using three different 3.6-s prepulses: −110 mV (red), −90 mV (blue), and −80 mV (green), and V_t of −50 mV. (b) Average current amplitudes exhibit a significant decrease after application of 1 μM Allo across different conditioning potentials. The inset shows the chemical structure of Allo (*P<0.05, ^†P<0.01, and ^‡P<0.001, two-way repeated measures analysis of variance followed by Holm-Sidak's post hoc test). (c) Steady-state inactivation curves (I/I_max) display a leftward shift upon application of Allo. (d) Original traces from a representative subicular neurone depicting active membrane responses to a 200 pA hyperpolarising stimulus in the absence (black trace), presence of Allo 3 μM (blue trace), and after drug wash-out (black trace). (d) The average number of rebound bursts and average number of rebound action potentials (e) was significantly decreased upon addition of Allo, whereas the average input resistance was not significantly affected (f). Results are expressed as mean (standard error of mean). *P<0.05 and ^†P<0.01, paired t-test.