Ethanol effects on local cerebral glucose utilization in high-alcohol-drinking and low-alcohol-drinking rats.

Divergent ethanol-drinking behavior in rats selectively bred for high- or low-ethanol-drinking behavior could be related to differences in the sensitivity of the CNS to ethanol. In the current study, we examined the effects of acute (i.e., single injection) ethanol administration on local cerebral glucose utilization (LCGU) within selected brain regions of high-alcohol-drinking (HAD) and low-alcohol-drinking (LAD) rats. Adult, male, HAD and LAD rats from replicate line 2 were injected intraperitoneally with saline, or ethanol, at doses of 0.25 g/kg or 1.0 g/kg, during their dark cycle; 10 min later, [14C]-2-deoxyglucose ([14C]-2-DG; 125 microCi/kg) was injected into the femoral vein. Timed arterial blood samples were collected over 45 min and assayed for plasma glucose, ethanol, and [14C]-2-DG levels. Rats were then decapitated, and their brains were quickly extracted and frozen in isopentane at -50 degrees C. Coronal brain sections were prepared and apposed to x-ray film for 2 days, and image densities were determined by using quantitative autoradiography. Data were collected from several key limbic (nucleus accumbens, ventral tegmental area, olfactory tubercle, amygdala, hippocampus, ventral pallidum, and septum), basal ganglia, cortical (medial prefrontal, frontal, parietal, temporal, occipital, entorhinal, piriform, and cingulate), and subcortical (thalamus, habenula, and superior colliculus) structures. After administration of both low (0.25 g/kg) and moderate (1.0 g/kg) doses of ethanol, LCGU values were lower, relative to those for saline controls, in several CNS regions (lateral septum; posterior cingulate, frontal, parietal, and temporal cortices; dorsomedial striatum; and dorsomedial thalamus) of LAD but not HAD rats. These findings may indicate that certain CNS regions of LAD-2 rats are more sensitive than regions of HAD-2 rats to the effects of low-to-intermediate doses of ethanol.

Local cerebral glucose utilization after relapse in ethanol drinking in alcohol-preferring (P) rats.

The [(14)C]-2-deoxyglucose ([(14)C]-2-DG) quantitative autoradiographic technique was used to determine rates of local cerebral glucose utilization (LCGU) in discrete brain regions of adult, male alcohol-preferring (P) rats after 2 weeks of ethanol deprivation (E-D), 3 and 14 days of ethanol-relapse drinking (E-R3; E-R14), and in P rats, which were chronically drinking ethanol (E-C) for 8 weeks during daily 3-h scheduled-access sessions to 15% (vol./vol.) ethanol and water, or were ethanol-naive (E-N). The hypothesis to be tested was that ethanol-relapse drinking is initiated to restore changes in functional activity back to their chronic ethanol-exposed state. The LCGU rates were measured 1 h before the scheduled-access session. Mean ethanol intake did not differ among the groups. The LCGU rates were decreased in 41 of 57 regions or subregions examined in E-C rats compared with findings for E-N rats, including subregions of the cerebral cortex, hippocampus, and structures in the mesocorticolimbic and nigrostriatal systems. After 2 weeks of deprivation, LCGU values tended to return toward control values (E-N) in most CNS regions and did not differ significantly from control values in 12 regions or subregions (e.g., parts of the limbic system, cerebral cortex). Compared with LCGU values that recovered toward control levels in the E-D group, ethanol-relapse drinking was associated with decreased LCGU values in (1) 4 of 10 limbic structures, (2) all 6 cerebral cortical regions, (3) 1 of 4 basal ganglia regions, (4) 2 of 7 hippocampus subregions, and (5) 1 of 6 thalamic nuclei. The present results indicate that ethanol-relapse drinking was associated with reduced LCGU rates in most CNS regions that recovered toward control values and suggested to us that ethanol-relapse drinking may be initiated to restore neuronal function to its prior chronic ethanol-exposure state.