Rationale: There is accumulating evidence that the neuropeptide urocortin 1 (Ucn1) is involved in alcohol consumption. Thus far, however, most studies have been performed in mice.
Objectives: The purpose of the present study was to characterize Ucn1 expression in rats selectively bred for either high or low alcohol intake.
Methods: Brains from naive male rats of five pairs of independently selected lines (iP/iNP, AA/ANA, HARF/LARF, HAD1/LAD1, and HAD2/LAD2) were analyzed by immunohistochemistry.
Results: Significant differences were found between iP/iNP, HARF/LARF, and HAD2/LAD2 in number of Ucn1-containing cells in the Edinger-Westphal (EW) nucleus (the main source of Ucn1 in the brain), whereas no significant differences were found between HAD1/LAD1 and AA/ANA. Similarly, significant differences in the optical density of Ucn1 immunoreactivity in EW were found between iP/iNP, HARF/LARF, and HAD2/LAD2, whereas no differences on this measure were found between HAD1/LAD1 and AA/ANA. In the lateral septum (LS, the main projection area of Ucn1-containing neurons in the rat), significant differences were found only between AA/ANA and HAD2/LAD2; however, a meta-analysis indicated that across all five lines, preferring animals had a significantly greater number of Ucn1-positive fibers than nonpreferring animals.
Conclusions: These results provide evidence that, in rats, Ucn1 may be involved in regulation of alcohol intake, and that this regulation may occur through the Ucn1 projections to LS.