Figure 2. Influence of GABA receptor agonists and antagonists on C4 nerve burst frequency in nicotine and saline-exposed preparations.

Average changes in C4 nerve burst frequency as a function of time in response to 250 μm muscimol (A), 60 μm pentobarbital sodium (Nembutal, B) and 8 μm bicuculline methiodide (C) in saline-exposed (•) and nicotine-exposed preparations (○). Drug application occurred between minutes 30 and 60 (vertical dashed lines in the top panel), and this period was bracketed by a 30 min baseline period and a 30 min period of drug washout. *Difference between nicotine-exposed and saline-exposed preparations at a given time point (P < 0.05). ⁺Frequency significantly different from baseline frequency within a group (P < 0.05). Baseline frequency was taken as the average of the 6 baseline data points, and statistical contrasts between this average baseline value and each subsequent data point were made for all three drugs. Bicuculline did not result in any significant differences, either within or between groups, although there is trend towards an increase in frequency in both groups.