Given that the amplitude of recorded currents was relatively Panobinostat chemical structure small (usually < 100 pA), the maximal voltage error in our voltage-clamp experiments was < 3 mV. Unless otherwise stated, all experiments were performed in the continuous presence of APV (50 μm) or MK801 (20 μm), CNQX (10 μm), gabazine (10 μm) and CGP55845 (1 μm) in order to block NMDA, AMPA, GABAA and GABAB receptors, respectively. In order to optimally isolate the outward SK current from KCa1, M-type and delayed rectifier K+ currents, 5 mm tetraethylammonium (TEA) was added to the superfusate
in voltage-clamp experiments (Sailer et al., 2002; Pedarzani et al., 2005). In slices, this concentration of TEA only slightly affects SK channels whereas it fully blocks other currents which would otherwise contaminate the SK currents (Blatz & Magleby, 1986; Lang & Ritchie, 1990; Leinders & Vijverberg, 1992; see Fig. 3). Neurons were sampled in the same region as described above. Flow rate was the same as above, but temperature was set slightly higher (34.0 ± 0.5 °C). Romidepsin in vitro Structures were visualized using a binocular microscope. The dorsal raphe nucleus was identified as a semilucent region, dorsal to the fasciculus longitudinalis medialis (Paxinos & Watson, 1998). Intracellular electrodes were also pulled using
a P-87 micropipette puller and borosilicate glass capillary tubing (1.0 mm OD, 0.5 mm ID; Prism capillaries, Dagan, Minneapolis, MN, USA). They were filled with 2 m KCl (resistance 70–150 MΩ). All recordings were made in the bridge-balance mode, using an NPI BA-1S amplifier (NPI Electronic GmbH, Tamm, Germany). Membrane potentials and injected currents were
digitized by a Powerlab 4/30 converter and recorded using LabChart7 (AD Instruments, Spechbach, Germany). The accuracy of the voltage measurement was checked by withdrawing the electrode from the neuron at the end of the recording. The measured voltage lay between −3 and +3 mV in all cases. No correction was made for these small errors. Membrane potential was set at −60 mV GPX6 using a continuous direct current injection (−20 to +20 pA, depending on the cell). Action potentials were evoked by short (3-ms) depolarizing pulses (+500–900 pA) using a Master-8 stimulator (A.M.P.I., Jerusalem, Israel). Drug effects on the mAHP were quantified as follows: the control amplitude of the mAHP was defined as the difference in mV between the value of membrane potential 70 ms after the peak of the action potential in control conditions and during superfusion of 300 nm apamin or 100 μm bicuculline methiodide (BMI, which has been shown to fully block SK channels at this concentration: Seutin & Johnson, 1999). Values of this parameter were monitored each minute during superfusion of various Ca2+ channel blockers. Concentration–response curves were analysed using GraphPad Prism (GraphPad Software,Inc., San Diego, CA, USA).