Fig. 3.

Propranolol stabilizes single-unit firing in the population of mPFC neurons. Spontaneous firing rates were averaged across all neurons and normalized to the preconditioning baseline for each brain region and treatment group. Fear conditioning (blue vertical bar) induced a dramatic increase in average spontaneous firing rate in PL neurons from vehicle-treated rats [A, black trace; Inset shows first 20-s postshock bin, comparing vehicle (white bar) with drug (red bar)] that was mitigated by propranolol treatment (A, red trace). Conditioning induced a weaker postshock increase in spontaneous firing in IL neurons from vehicle-treated rats (B, black trace; Inset shows first 20-s postshock bin) and produced an enduring suppression of this activity. Propranolol treatment (B, red trace) counteracted both types of firing rate changes in IL. Injection (INJ) is denoted by green vertical bar; conditioning (tone-shock pairings) is denoted by blue vertical bar. Data during the conditioning period were not recorded. *P < 0.05 vs. vehicle. All values are means (±SEM for insets).