Prelimbic Cortical Injections of a GABA Agonist and Antagonist: In Vivo Quantification of the Effect in the Rat Brain Using [(18)F] FDG MicroPET.

PURPOSE

We evaluated the glucose metabolism after microinjections of a GABAA antagonist, bicuculline, and a GABAA agonist, muscimol, in the rat prelimbic cortex (PL) by small animal positron emission tomography (μPET).

PROCEDURES

Following a microinjection of either 0.5 μl bicuculline (0.1 mg/ml), muscimol (1 mg/ml), or saline in the left PL of 11 healthy male Sprague Dawley rats (250-275 g), 2-deoxy-2-[(18)F]fluoro-β-D-glucose ([(18)F]FDG) PET images were acquired. Volume-of-interest (VOI)-based analysis and voxel-based statistical parametric mapping were performed (n = 9).

RESULTS

VOI-based analysis revealed significantly different [(18)F]FDG uptake following bicuculline versus muscimol in PL (p < 0.001), infralimbic cortex (p < 0.01), and cingulate cortex (p < 0.01). Voxel-based analysis showed bicuculline induced widespread significant hypermetabolism throughout the brain while muscimol induced significant localized hypometabolism.

CONCLUSIONS

Here, we visualize functional GABAA-mediated correlations of the PL following pharmacological stimulation. This could serve as a reference and shed light on the working and focality of other stimulation paradigms targeting this region.