Fig. 1.

Inhibition of the small-conductance calcium-activated potassium channel by apamin (100 nm) significantly enhanced firing in lateral dorsal striatum (latDS) neurons, but had a smaller effect in nucleus accumbens shell (NAS) neurons. (A and B) The interspike interval (ISI) was greater in latDS than in NAS neurons at baseline, and apamin reduction of the ISI was greater in latDS than in NAS neurons. The ISI was determined at the lowest current step that elicited at least two action potentials (APs). bas, baseline; apa, apamin. (C and D) The apamin-dependent increase in AP firing was greater in latDS than in NAS neurons. The number of APs was determined at a current step at which three APs were generated (or four APs, if no current step produced three APs). (E–G) The slope relationship between input current and number of evoked spikes (the input–output slope), determined from the last subthreshold pulse and the first three suprathreshold pulses (E and F), was significantly smaller in latDS than in NAS neurons (G), and the apamin-dependent enhancement of the input–output slope was significantly greater in latDS than in NAS neurons (G). Data in E and F correspond to the traces shown in A. *P < 0.05, **P < 0.01.