Lesioning of midbrain raphe nuclei with 5,7-DHT fails to alter ethanol intake in the low alcohol drinking (LAD) rat.

1. The effect of 10 g 5,7-dihydroxytryptamine (5,7-DHT) micro-injected into both the dorsal (DRN) and the median raphe nuclei (MRN) on the intake of ethanol in the low alcohol drinking (LAD) rat was measured using a standard 3-30% ethanol preference test. 2. The combined lesion of both midbrain structures depleted the levels of serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) significantly in each of eight major regions of the brain. The levels of norepinephrine, dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) remained unchanged after the lesion. 3. The effects of the neurotoxin lesions on the intakes of ethanol, food, water and total amount of fluid consumed were not significant. 4. The results corroborate our previous findings with the Sprague-Dawley strain of rat and suggest that although brain 5-HT may play a role in the maintenance of basal patterns of ethanol drinking, this monoamine may not be able to modify further the consumption of this fluid after lesioning with 5,7-DHT.