Fig. 3. Somatic behaviors reduce GCaMP signaling from IPN GAD2+ neurons during nicotine withdrawal.

GCaMP responses were analyzed during bouts of somatic behaviors in nicotine-withdrawn mice and following saline injections. We focused our analysis on somatic behaviors that had an average duration of >2 s which included grooming, scratching, digging, and chewing. A–D Mecamylamine increased time spent grooming and digging in comparison to saline. There was also a trend to increased scratching time but no change in chewing time following mecamylamine vs saline administration. We recorded GCaMP activity of IPN GAD2+ neurons time-locked to somatic events following mecamylamine (E) and saline injection (F). Z-score plots were generated from all somatic events included in the analysis for grooming, scratching, digging, and chewing following mecamylamine (G, I, K, M) and saline injections (H, J, L, N). Plots show the z-scores from 2 s prior to the onset of each behavior (onset indicated by an arrow) until 4 s post onset. Comparisons were made using an average z-score per animal (n = 9–13) that was calculated from all events of each behavior. Following mecamylamine injection, we observed significant decreases in GCaMP activity 2–4 s post-onset of grooming compared to pre-onset (G). No significant difference in GCaMP activity pre- and post-onset of grooming occurred following saline injection (H). Significant reductions in GCaMP signaling were observed post-onset of scratching behavior compared to pre-onset following mecamylamine (I) but not saline injection (J). No difference in GCaMP activity was observed post-onset of digging and chewing events compared to pre-onset following mecamylamine (K, M) or saline injection (L, N). MEC mecamylamine, SAL saline.