Effect of lesions of the dorsalis raphe nuclei on the initiation of alcohol preference in rats.
In this report, the effect of lesion of the dorsalis raphe nuclei (DR) by stereotaxic injection of kainic acid on the initiation of voluntary ethanol consumption is described for male rats. After a 30-day recovery period DR- and control-rats were exposed to a 0.2% saccharin sodium--water--5% ethanol free choice test (8 days) for the first time. This three-choice paradigm revealed a positive preference for ethanol (50.5%) vs. saccharin (29.5%) and water (20.0%) in control rats. However, in the group showing histological evidence of DR lesion there was no preference for ethanol (25.7%) whereas total fluid intake/8 days was not affected. These findings suggest a specific effect of the DR lesion on ethanol preference in naive rats. In addition, the within-group analysis of data revealed that such effects were due to an increase in the population of spontaneous non-alcohol-preferring subjects (ethanol preference between 0 and 20%) and to prevention of alcohol-preferring rats (ethanol preference between 80-100%). The depletion of brain serotonin (5-HT) found in the forebrain of the DR-lesioned rats suggests that 5-HT pathways projecting from the DR neurons may be involved in these effects. The fact that forebrain noradrenalin was not affected would rule out involvement of lesions of locus coeruleus-noradrenalin neurons by diffusion of kainic acid. However, the eventual lesion of peptide neurons in the periventricular gray substance surrounding the DR nuclei cannot be discounted.
Laboratorio de Investigaciones Cerebrales, Universidad Nacional de Cuyo, Mendoza, Argentina.
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Rodríguez Echandía
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D000428:Alcohol Drinking / Q000502:physiology*; D000818:Animals; D001931:Brain Mapping; D002755:Choice Behavior / Q000502:physiology*; D008297:Male; D011903:Raphe Nuclei / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains