Impaired hippocampal glucoregulation in the cannabinoid CB1 receptor knockout mice as revealed by an optimized in vitro experimental approach.
Journal of Neuroscience Methods. 2012-03-01; 204(2): 366-373
DOI: 10.1016/j.jneumeth.2011.11.028
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Lemos C(1), Valério-Fernandes A, Ghisleni GC, Ferreira SG, Ledent C, de Ceballos ML, Köfalvi A.
Author information:
(1)Center for Neuroscience and Cell Biology of Coimbra, Faculty of Medicine, University of Coimbra, 3004-517 Coimbra, Portugal.
Several techniques exist to study the rate of glucose uptake and metabolism in
the brain but most of them are not sufficiently robust to permit extensive
pharmacological analysis. Here we optimized an in vitro measurement of the
simultaneous accumulation of the metabolizable and non-metabolizable (3)H and
(14)C d-glucose analogues; permitting convenient large-scale studies on glucose
uptake and metabolism in brain slices. Next, we performed an extensive
pharmacological characterization on the putative glucoregulator role of the
endocannabinoid system in the hippocampal slices of the rat, and the wild-type
and the CB(1) cannabinoid receptor (CB(1)R) knockout mice. We observed that
(3)H-3-O-methylglucose is a poor substrate to measure glucose uptake in the
hippocampus. (3)H-2-deoxyglucose is a better substrate but its uptake is still
lower than that of (14)C-U-d-glucose, from which the slices constantly metabolize
and dissipate (14)C atoms. Thus, uptake and the metabolism values are not to be
used as standalones but as differences between a control and a treatment. The
CB(1)R knockout mice exhibited ∼10% less glucose uptake and glucose carbon atom
dissipation in comparison with the wild-type mice. This may represent congenital
defects as acute treatments of the rat and mouse slices with cannabinoid
agonists, antagonists and inhibitors of endocannabinoid uptake/metabolism failed
to induce robust changes in either the uptake or the metabolism of glucose. In
summary, we report here an optimized technique ideal to complement other
metabolic approaches of high spatiotemporal resolution. This technique allowed us
concluding that CB(1)Rs are at least indirectly involved in hippocampal
glucoregulation.