Hypoexpression of benzodiazepine receptors in the amygdala of neophobic BALB/c mice compared to C57BL/6 mice

The distribution of benzodiazepine receptors in the brain of neophobic BALB /c mice was studied by autoradiographic analysis using [H-3]-diazepam and c ompared to that of the same receptors of the "nonemotional" C57BL/6 mice. T his technique revealed no significant interstrain difference except for a l ower density of diazepam binding sites in the amygdala of BALB/c mice. Ther efore, the expression of benzodiazepine receptors in the amygdala of the tw o strains of mice were quantified by binding studies on brain membranes. Th e amygdala of BALB/c mice exhibited a fivefold decrease in the density of b enzodiazepine receptors compared to C57BL/6 mice. These results suggest tha t the trait anxiety (neophobia) that characterizes BALB/c mice could be due , at least in part, to a genetic modulation of benzodiazepine receptor expr ession in the amygdala, a structure known to be strongly involved in fear b ehavior. (C) 1999 Elsevier Science Inc.