Article Figures & Data
Figures
- Fig. 1.
Placements of electrode and microdialysis probes, depiction of stimulus parameters, and glutamate efflux during BLA stimulation. Locations of electrode tips (●) and linesrepresenting the active surface of microdialysis probes for all animals used in the study are illustrated. Electrode placement was ipsilateral to microdialysis probes in all experiments, but in different rats, placements were made randomly in either the left or right hemisphere.a, Electrode placements were confined to the basolateral amygdala complex. b, PFC probe placements were primarily in infralimbic/prelimbic regions of the medial PFC. c, NAc probe placements were along the border of the shell and medial core. d, BLA stimulation consisted of brief bursts of 50 μA current pulses over a period of 10 min. e, BLA stimulation significantly increased glutamate efflux in the PFC (F = 4.53; p < 0.01;n = 15). f, BLA stimulation also increased glutamate efflux in the NAc (F = 1.69;p < 0.05; n = 10).
- Fig. 2.
Dopamine release during BLA stimulation. BLA stimulation increased extracellular levels of dopamine in both the PFC (F = 6.09; p < 0.01;n = 10) and the NAc (F = 4.65;p < 0.01; n = 10). However,post hoc analysis revealed that NAc dopamine levels did not increase during the period of BLA stimulation when compared with baseline. Asterisks indicate significant differences from baseline (p < 0.05).
- Fig. 3.
Effect of intra-PFC perfusion of mGluR2/3 agonist LY354740 on glutamate efflux in the PFC during BLA stimulation. Reverse dialysis of LY354740 (1 μm) reduced the glutamate efflux evoked by BLA stimulation (solid line;n = 7) as compared with control animals (dotted line; n = 15) (also depicted in Fig. 1). Two-way repeated-measures ANOVA revealed a significant difference between the groups (F = 12.04;p < 0.01). Asterisks indicate individual samples that were significantly different between groups (p < 0.05). [Of note, we were able to detect LY354740 levels in our HPLC system that were used to detect glutamate, and therefore we were able to confirm that LY354740 did not diffuse from the PFC to the NAc because, during the time that the compound was perfused into the PFC, it was not detected in the dialysate obtained from the probe implanted in the NAc (data not shown).]
- Fig. 4.
Effects of local perfusion into PFC of mGluR2/3 agonist LY354740 (1 μm) and AMPA antagonist LY293558 (100 μm) on dopamine efflux in the NAc and PFC during BLA stimulation. Drug perfusion began at least 1 hr before BLA stimulation.a, BLA stimulation increased NAc dopamine efflux with either the mGluR2/3 agonist in the PFC (solid line, ■) (F = 3.72; p < 0.01;n = 9) or the AMPA antagonist in the PFC (solid line, ▪) (F = 4.26;p < 0.01; n = 6). This increase was in contrast to the lack of immediate dopamine increase during BLA stimulation in control rats (dotted line) (also depicted in Fig. 2.). Asterisks indicate significant differences between the control and the other two groups (p < 0.05). b, In the PFC, dopamine increase was evoked by BLA stimulation in the presence of either the mGluR2/3 agonist (solid line, ■) (F = 11.9; p < 0.01;n = 8) or the AMPA antagonist (solid line, ▪) (F = 2.22; p< 0.05; n = 8). There were no significant differences between these groups and the control group.
Tables
- Table 1.
Behaviors observed during microdialysis sample collection in the 10 min periods during and after BLA stimulation
Behaviors Controls LY354740 LY293558 During After During After During After Ambulation 63 0 13* 0 33 Grooming 0 59 0 25 0 11* Freezing 96 56 94 81 100 56 Sniffing 48 63 6* 50 22 56 Mouth movement 63 26 81 69* 100* 67* Jaw tremor 48 33 31 38 78* 89* Data are presented as percentages of animals that exhibited selected behaviors within each group. The control group (n = 27) had normal Ringer's perfused into the microdialysis probe implanted in the PFC. In the other two groups, either the mGluR2 agonist LY354740 (n = 16) or the AMPA/kainate antagonist LY293558 (n = 9) was added to the Ringer's solution that was perfused into the PFC. All animals were at rest for the 10 min period before BLA stimulation (data not shown). Asterisks denote significant differences (p < 0.05) compared with the control group.
