Module 10: Figure neuronal SK channel function

The role of small-conductance (SK) channels in modulating the firing frequency of CA1 hippocampal neurons.

The activation of the apamin-sensitive small-conductance (SK) channels and apamin-insensitive channels regulates the firing pattern of CA1 hippocampal neurons. A. Following a 400 ms depolarizing current pulse, the control displays a fast after-hyperpolarizing potential (fAHP) (closed arrowhead) followed by a slow after-hyperpolarizing potential (sAHP) (open arrowhead). The fast early response was reduced by apamin, whereas the slower response was completely suppressed by an analogue of cyclic AMP. B. These two hyperpolarizing responses affect the firing pattern in two ways. Under control conditions, an 800 ms depolarizing pulse induces a brief burst of four action potentials. Addition of apamin to reduce the fast AHP resulted in a small increase in firing frequency, whereas inhibition of the slow AHP with 8CPT-cyclic AMP abolished the adaptation process, resulting in a prolonged burst of firing. Reproduced, with permission, from Stocker, M., Krause, M. and Pedarzani, P. (1999) An apamin-sensitive Ca2+-activated K+ current in hippocampal pyramidal neurons. Proc. Natl. Acad. Sci. U.S.A. 96:4662–4667. Copyright (1999) National Academy of Sciences, U.S.A.; see Stocker et al. 1999.