Figure 8.

α3β4* and/or α4* nAChRs drive nicotine-elicited firing in MHbVL neurons. A, Cell-attached recordings from MHbVL (n = 8) and MHbVC (n = 8) neurons were established, and baseline firing was recorded for several minutes, followed by superfusion of nicotine (1 μm). Normalized firing rate is plotted, with baseline firing before nicotine application set to 1.0. B, Cell-attached recordings from α4 KO MHbVL neurons (n = 9) were conducted. As in A, baseline firing was recorded followed by firing in response to superfusion of 1 μm nicotine. Data from MHbVL WT neurons shown in A are replotted for reference using dashed lines and no symbols. C, Cell-attached recordings from WT MHbVL neurons (n = 6) were conducted in response to SR16584, a putative α3β4* nAChR antagonist. Baseline firing was recorded for several minutes, followed by superfusion of SR16584 (20 μm), then superfusion of nicotine (1 μm) plus SR16584. Data from MHbVL WT neurons shown in A (response to 1 μm nicotine alone) are replotted for reference using dashed lines and no symbols. D, Representative traces from cell-attached firing experiments described in A–C. A sample current trace from t = 2.5 min (baseline) and t = 10 min (in 1 μm nicotine) is shown for the indicated cell type, genotype, and/or pharmacological treatment. Calibration: 20 pA, 200 ms. E, Quantification of data shown in A–C. For each cell from each of 4 conditions described in A–C, the fold change in action potential firing was derived compared with predrug firing. A bar graph is shown for these 4 conditions. *p < 0.05 (paired t test comparing predrug firing and peak firing during drug application for each cell).