Effect of WIN 55212-2 microinjection into the BNST on neuronal impulse activity evoked by infralimbic cortex stimulation. A, Diagram of the stimulation, microinfusion, and recording protocol used in this experiment. Here, the IL was stimulated with a 100-pulse train, and WIN 55212-2 (WIN, 500 μm) was microinfused within the BNST in a total volume of 20–30 nl >15 s. B, Typical PSTHs showing ILCx-evoked excitation in a typical BNST neuron projecting to the VTA, before (Basal) and after intra-BNST infusion of WIN 55212-2 (30 pmol/20 nl). Intra-BNST CB receptor activation inhibited excitation of BNST neurons evoked by ILCx stimulation. C, Time course of effects of intra-BNST WIN 55212-2 infusion on evoked BNST neuronal impulse activity. Local infusion of WIN 55212-2 (infused at time 0, black bars) into the BNST induced a prolonged reduction of evoked impulse activity in BNST neurons compared with baseline (white bars). Data are expressed as percentage of mean response magnitude and are the mean ± SEM. None of the cells returned to predrug level (n = 13); values are significantly different from baseline from 10 min after WIN 55212-2 (**p < 0.01; ANOVA followed by Dunnett's test). Note the subsequent reversal by SR141716A (1 mg/kg, i.v.; injected at time 15 min, gray bars). D, E, Overall effects of intra-BNST infusion of VEH, WIN 55212-2, WIN 55212-2 plus systemic SR141716A and systemic SR141716A alone on evoked (D) and spontaneous (E) BNST neuronal impulse activity. The scores plotted are the change in response magnitude (D) or firing frequency (E) postdrug as a percentage of predrug rates. Intra-BNST WIN 55212-2 injection induced a 50% inhibition of evoked response magnitude (C) and spontaneous firing frequency (D). Note that SR141716A treatment had no effect by itself on evoked responses and spontaneous firing frequency. ANOVAs followed by Newman–Keuls tests for pairwise comparisons were performed for evoked responses and spontaneous firing frequency. **p < 0.001 versus control group (VEH treatments). Numbers of neurons recorded in each group are mentioned in parentheses above each histogram bar. REC, Recording electrode.
